Logo

Prop issue mercury 115 el pto

Maurice Helou

New member
1997 Cherokee ranger 18 with 1997 mercury 115 el pto w/ lazer11 13.5x22 prop. Ran Excellant smooth 5000 rpm for years. Then the problem, 5000 rpm would not plane, felt like being held back. Replaced hub, same problem. Replace prop with 21 pitch alluminum, ran fine, plane out at 4800 rpm. Rebalanced lazer 11, it needed very little adjustment. Put the original lazer 11 on, same problem, revs to 5000 rpm would not go very fast felt like being held back. Put the alluminum prop on all issues went away. Question, why is lazer 11 not performing, after many years of performance, yet the alluminum prop works well. What is the common denominator. The motor produces no abnormal noise, runs and idles smooth.
 
What you failed to mention was rpm increase with reduction in mph. Had you said that, the obvious answer would be a spun hub on the Laser II prop. Based upon your input, think about what I said. I see no other solution with the input you have provided.

Mark
 
First, the hub was replaced and did not correct the problem.
With alum 21p prop rpm is 3800 to 4000 and speed is 32 mph.
With lazer 11 The problem is intermittent; first as I punch the gas the motor will rev to 5000 rpm and speed is 10 mph and of course does not plane. After idle back to neutral several times and then punch the gas I may plane out at 4000 rpm and about 32 mph.

In the past the lazer11 worked with no issues, rpm was 5000 and speed in excess of 32 mph.
What else should I be checking.?
 
Okaye. How big are the ports in the Laser II? How big were they when you had no issues with the prop?

Mark

the lazer is an older model prop, the ports are square. There were never any plugs when we were running 5000/5200 and close to 40mph. I see the newer lazer ports are round and have plugs. Are there plugs made for the older style prop and should I try and locate them and use the plugs? Won't using the plugs defeat the purpose of the ports, which is to exit exhaust thus causing bubbles to break up water and allow a faster plane. Let me end by saying I am a newbe and thanks for your help.
 
The hole size determines the amount of what you said. With no holes, no exhaust gas to reduce the density of the water across the blades, no rise in rpms, engine lugs in the hole shot and duration is lengthy when running a prop made for a BB on the pad at WOT which you have.

Flip side is too much exhaust causing the prop to ventilate and you get minimal thrust and if bad enough not even completing the hole shot. Trick is to get the hole size to match your setup and your rig.

First of all the manual lists your engine at 5250 upper end of rated rpms at WOT. Sounds like you are there on rpms. However, running your numbers: 2:1 gearbox, 5200 rpm, 22P prop comes with a no slip speed of 54. Checking your 40 mph vs no slip of 54 yields 28% slip.

I ran the 21 inch pitch of that prop at 6000 rpm on my Ranger 17' Fisherman, Direct Charged I6 115, 99 cu in. with the pad right at 50. Our engine hull combinations are very similar. So my numbers were 2, 6000, 21, no slip of 60, actual 50, slip 17%. My boat was new in 1989 and the prop came with it. As I recall it had 5/16 to 3/8" round holes. I seldom tucked her all the way in. Usually parallel to the pad for the hole shot. I usually boated alone and that could make some difference. I'd firewall it in the hole and rpms would jump up fast to several hundred (give or take 300...see later) rpms over what I thought was normal. Hole shot was stellar and engine was holding the extra rpms. After on plane, I punched her all the way out till just before I started ventilating with too much trim. Rpms were around 6300 during that time for a few seconds and then the bubbles would be locked out, the prop would bite solid water, the rpms would drop to 6000 and away I went.

You can seal the holes off with something like JB weld and then start drilling them out. I'd start with 5/16 and move up in 1/16 inch steps till you get to where you are now with the width of the square holes you mentioned. If you have a battery operated drill I'd take bits as mentioned with me to your boating area having drilled the 5/16 at home where it would be easier to get it as straight in alignment as you could. Then enlarging at the lake would not that big of a deal. I'd make a test run with each diameter, varying trim position coming out of the hole and recording rpms, time to plane out, and top speed which shouldn't have changed. Then back to the dock, drill out to the next size and do it again. Don't know how long the JB will stay in the hole so I'd make it quick.

Then come back with the numbers and lets go from there. The 28% slip still bothers me as that is a heck of a lot of slip for that hull/engine combination especially with a new hub. Got a GPS? Check your speed with that. On your tach, that engine is spec'd to idle at 675 +/- 25 so if you are anyway near that it is probably ok. Stator is 12pole if you have an adjustable model. I ran the Quicksilver OEM.

Mark
 
The hole size determines the amount of what you said. With no holes, no exhaust gas to reduce the density of the water across the blades, no rise in rpms, engine lugs in the hole shot and duration is lengthy when running a prop made for a BB on the pad at WOT which you have.

Flip side is too much exhaust causing the prop to ventilate and you get minimal thrust and if bad enough not even completing the hole shot. Trick is to get the hole size to match your setup and your rig.

First of all the manual lists your engine at 5250 upper end of rated rpms at WOT. Sounds like you are there on rpms. However, running your numbers: 2:1 gearbox, 5200 rpm, 22P prop comes with a no slip speed of 54. Checking your 40 mph vs no slip of 54 yields 28% slip.

I ran the 21 inch pitch of that prop at 6000 rpm on my Ranger 17' Fisherman, Direct Charged I6 115, 99 cu in. with the pad right at 50. Our engine hull combinations are very similar. So my numbers were 2, 6000, 21, no slip of 60, actual 50, slip 17%. My boat was new in 1989 and the prop came with it. As I recall it had 5/16 to 3/8" round holes. I seldom tucked her all the way in. Usually parallel to the pad for the hole shot. I usually boated alone and that could make some difference. I'd firewall it in the hole and rpms would jump up fast to several hundred (give or take 300...see later) rpms over what I thought was normal. Hole shot was stellar and engine was holding the extra rpms. After on plane, I punched her all the way out till just before I started ventilating with too much trim. Rpms were around 6300 during that time for a few seconds and then the bubbles would be locked out, the prop would bite solid water, the rpms would drop to 6000 and away I went.

You can seal the holes off with something like JB weld and then start drilling them out. I'd start with 5/16 and move up in 1/16 inch steps till you get to where you are now with the width of the square holes you mentioned. If you have a battery operated drill I'd take bits as mentioned with me to your boating area having drilled the 5/16 at home where it would be easier to get it as straight in alignment as you could. Then enlarging at the lake would not that big of a deal. I'd make a test run with each diameter, varying trim position coming out of the hole and recording rpms, time to plane out, and top speed which shouldn't have changed. Then back to the dock, drill out to the next size and do it again. Don't know how long the JB will stay in the hole so I'd make it quick.

Then come back with the numbers and lets go from there. The 28% slip still bothers me as that is a heck of a lot of slip for that hull/engine combination especially with a new hub. Got a GPS? Check your speed with that. On your tach, that engine is spec'd to idle at 675 +/- 25 so if you are anyway near that it is probably ok. Stator is 12pole if you have an adjustable model. I ran the Quicksilver OEM.

Mark

This is still bugging me. What you said about all the years you ran the prop and it worked fine. You had the holes I am assuming just as they are today. You swapped props and the problem disappeared. Obviously the prop is the smoking gun. You had the hub replaced, but is it holding?

Get a marker of some sort, permanent marker, scribe a line if necessary on the rear of the prop extending from the brass splined area out to the SS inner barrel. Run it ensuring that it causes the same problem. Take it back off and check your line. If it is no longer straight, the new hub is slipping also. Gotta be it man.

Mark
 
First, the hub was replaced and did not correct the problem.
With alum 21p prop rpm is 3800 to 4000 and speed is 32 mph.
With lazer 11 The problem is intermittent; first as I punch the gas the motor will rev to 5000 rpm and speed is 10 mph and of course does not plane. After idle back to neutral several times and then punch the gas I may plane out at 4000 rpm and about 32 mph.

In the past the lazer11 worked with no issues, rpm was 5000 and speed in excess of 32 mph.
What else should I be checking.?

This has slipping hub written all over it. "first as I punch the gas the motor will rev to 5000 rpm and speed is 10 mph"....you are putting max thrust against the prop with max resistance against it...sitting in the water having to get the boat moving and having to move a large quantity of water out of the way.

"After idle back to neutral several times and then punch the gas I may plane out at 4000 rpm and about 32 mph." Here you seat and reseat the hub until it finds enough friction to hold onto the outer hub. More slipping prop syndrome. That's how they work when you hit something. The rubber slips in the hub disconnecting the drive shaft from the hub of the prop protecting it. You cut it back to idle to let the rubber reseat, put the throttle back to it and away you go....when the rubber to hub interface are working correctly.

Your 28% slip that the BAM prop slip calculator measured. More slip.

Run the scribed line test. I bet you will fail it and your Laser will go back to the prop shot to have them do it right this time.

Mark
 
This has slipping hub written all over it. "first as I punch the gas the motor will rev to 5000 rpm and speed is 10 mph"....you are putting max thrust against the prop with max resistance against it...sitting in the water having to get the boat moving and having to move a large quantity of water out of the way.

"After idle back to neutral several times and then punch the gas I may plane out at 4000 rpm and about 32 mph." Here you seat and reseat the hub until it finds enough friction to hold onto the outer hub. More slipping prop syndrome. That's how they work when you hit something. The rubber slips in the hub disconnecting the drive shaft from the hub of the prop protecting it. You cut it back to idle to let the rubber reseat, put the throttle back to it and away you go....when the rubber to hub interface are working correctly.

Your 28% slip that the BAM prop slip calculator measured. More slip.

Run the scribed line test. I bet you will fail it and your Laser will go back to the prop shot to have them do it right this time.

Mark

Ok - I got it, let me go to work on the process. I am thinking we have it narrowed down.
Thanks Mark
 
The hole size determines the amount of what you said. With no holes, no exhaust gas to reduce the density of the water across the blades, no rise in rpms, engine lugs in the hole shot and duration is lengthy when running a prop made for a BB on the pad at WOT which you have.

Flip side is too much exhaust causing the prop to ventilate and you get minimal thrust and if bad enough not even completing the hole shot. Trick is to get the hole size to match your setup and your rig.

First of all the manual lists your engine at 5250 upper end of rated rpms at WOT. Sounds like you are there on rpms. However, running your numbers: 2:1 gearbox, 5200 rpm, 22P prop comes with a no slip speed of 54. Checking your 40 mph vs no slip of 54 yields 28% slip.

I ran the 21 inch pitch of that prop at 6000 rpm on my Ranger 17' Fisherman, Direct Charged I6 115, 99 cu in. with the pad right at 50. Our engine hull combinations are very similar. So my numbers were 2, 6000, 21, no slip of 60, actual 50, slip 17%. My boat was new in 1989 and the prop came with it. As I recall it had 5/16 to 3/8" round holes. I seldom tucked her all the way in. Usually parallel to the pad for the hole shot. I usually boated alone and that could make some difference. I'd firewall it in the hole and rpms would jump up fast to several hundred (give or take 300...see later) rpms over what I thought was normal. Hole shot was stellar and engine was holding the extra rpms. After on plane, I punched her all the way out till just before I started ventilating with too much trim. Rpms were around 6300 during that time for a few seconds and then the bubbles would be locked out, the prop would bite solid water, the rpms would drop to 6000 and away I went.

You can seal the holes off with something like JB weld and then start drilling them out. I'd start with 5/16 and move up in 1/16 inch steps till you get to where you are now with the width of the square holes you mentioned. If you have a battery operated drill I'd take bits as mentioned with me to your boating area having drilled the 5/16 at home where it would be easier to get it as straight in alignment as you could. Then enlarging at the lake would not that big of a deal. I'd make a test run with each diameter, varying trim position coming out of the hole and recording rpms, time to plane out, and top speed which shouldn't have changed. Then back to the dock, drill out to the next size and do it again. Don't know how long the JB will stay in the hole so I'd make it quick.

Then come back with the numbers and lets go from there. The 28% slip still bothers me as that is a heck of a lot of slip for that hull/engine combination especially with a new hub. Got a GPS? Check your speed with that. On your tach, that engine is spec'd to idle at 675 +/- 25 so if you are anyway near that it is probably ok. Stator is 12pole if you have an adjustable model. I ran the Quicksilver OEM.

Mark

Mark, I have installed the Quicksilver OEM rubber plugs and will be testing in the next week.
Are you suggesting that I pre drill all 3 plugs to 5/16 on my bench and then run the first test. As I make drilling adjustments should I be drilling all 3 plugs to the next size at the same time?
Mo
 
Mark, I have installed the Quicksilver OEM rubber plugs and will be testing in the next week.
Are you suggesting that I pre drill all 3 plugs to 5/16 on my bench and then run the first test. As I make drilling adjustments should I be drilling all 3 plugs to the next size at the same time?
Mo

First test should be solid plugs to get a bench mark. Take data: What is the current load in the boat...folks fuel etc.

Try to keep these parameters constant during all the testing. Ambient temp if you think it will change significantly during your tests.....hotter it is, lower HP your engine produces so sloppier the performance will be.

How long from firewall till bow goes down on hole shot? Expect numbers in the 5 second give or take area. Maybe not initially, but when we are finished; looking for less time actually.

Engine rpms during hole shot. I realize they will increase as the boat speed increases, but do the best you can to capture them initially when you firewall it and what they are when the bow goes down.

Boat speed as bow lowers.

Other thing that you might want to notice, is once on plane, how long does it take for the prop to lock up....rpms will drop and speed will pick up proportionally.....you won't get this data point with no holes, but after you start drilling, be interesting piece of info.

Once you have that data let's look at it and then start drilling holes. Yes, all holes need to be the same size at the same time to equalize the load on the props. Otherwise you will surely have some prop vibrations.

Trim is an important part of this so in each of your tests, take a run with the trim all the way in till the bow drops, and then trim the engine parallel with the boat and do the hole shot again. A lot of times I get a better hole shot with it level vs tucked in as the engine ventilates better and the rpms come up faster. Also, if the engine ventilates while you are shooting, the boat will porpoise somewhat and every time it does, it sucks in more air but rpms increase significantly and when the stern goes back down, the prop is spinning a lot faster and you get a jolt forward. Once we get this right and you experience it a few times you will love it. I do!

Then we will decide to move on and if so, drill out 3 ea. 5/16 holes and take the same data under the same conditions as best you can. We will look at the numbers and if it's time to stop we will. Otherwise we will increase 1/16" on all 3 plugs at a time and continue testing.

Or if you want to spring for another set of plugs, we can go overboard just to see the upper limit and come back if necessary. One thing I am particularly interested in is the change in hole shot rpms between each test. Interested in hole shot time also, but rpms is what I am really interested in. You want to get your rpms up to get your ponies pushing the prop, but as I said before, if they get too high it just signals that you are loosing too much thrust via excessive exhaust gasses over the blades and it will delay the time of the shot.

Let's make it happen.

Mark
 
First test should be solid plugs to get a bench mark. Take data: What is the current load in the boat...folks fuel etc.

Try to keep these parameters constant during all the testing. Ambient temp if you think it will change significantly during your tests.....hotter it is, lower HP your engine produces so sloppier the performance will be.

How long from firewall till bow goes down on hole shot? Expect numbers in the 5 second give or take area. Maybe not initially, but when we are finished; looking for less time actually.

Engine rpms during hole shot. I realize they will increase as the boat speed increases, but do the best you can to capture them initially when you firewall it and what they are when the bow goes down.

Boat speed as bow lowers.

Other thing that you might want to notice, is once on plane, how long does it take for the prop to lock up....rpms will drop and speed will pick up proportionally.....you won't get this data point with no holes, but after you start drilling, be interesting piece of info.

Once you have that data let's look at it and then start drilling holes. Yes, all holes need to be the same size at the same time to equalize the load on the props. Otherwise you will surely have some prop vibrations.

Trim is an important part of this so in each of your tests, take a run with the trim all the way in till the bow drops, and then trim the engine parallel with the boat and do the hole shot again. A lot of times I get a better hole shot with it level vs tucked in as the engine ventilates better and the rpms come up faster. Also, if the engine ventilates while you are shooting, the boat will porpoise somewhat and every time it does, it sucks in more air but rpms increase significantly and when the stern goes back down, the prop is spinning a lot faster and you get a jolt forward. Once we get this right and you experience it a few times you will love it. I do!

Then we will decide to move on and if so, drill out 3 ea. 5/16 holes and take the same data under the same conditions as best you can. We will look at the numbers and if it's time to stop we will. Otherwise we will increase 1/16" on all 3 plugs at a time and continue testing.

Or if you want to spring for another set of plugs, we can go overboard just to see the upper limit and come back if necessary. One thing I am particularly interested in is the change in hole shot rpms between each test. Interested in hole shot time also, but rpms is what I am really interested in. You want to get your rpms up to get your ponies pushing the prop, but as I said before, if they get too high it just signals that you are loosing too much thrust via excessive exhaust gasses over the blades and it will delay the time of the shot.

Let's make it happen.

Mark
Mark
The saga continues, for the good and bad news. I plugged the Lazer 11 and idled 10 min to the wake zone, all well so far. Next I slowly applied throttle, she up and plained quickly reaching 4800 rpm, thats 800 to 1000 rpm better than on the alum prop and almost to where it was before this all started. No issues at previously stated. Ran about 400 yards made a smooth turn on the return back to the no wake zone. The engine began running rough and shaking I quickly idled back down. There was a clicking sound, I then shut it down. All that took place in about 20 seconds. Tilted the motor up, dropped the trolling motor down and made it back to the dock. I check the prop, the nut was tight and in place, the tabs down and in place and no irregular movement. Prop turns clockwise there was a click on each rotation. Will not turn counter clockwise. Thats my story. This morning I am off to the marina and have them pick up the boat. Based on the limited info what could I be looking at, Lower Unit rebuild or something less sinister. I haven't check oil in the lower unit. Will leave that up to the tech.
Your thoughts would be appreciated.
 
In F gear you have an overrun clutch. You experienced it. CCW the prop is locked to the flywheel. CW it ratchets and moves slightly in and out. When you are on plane for instance and cut the throttle, the prop is locked to the water flowing past it causing it to keep turning. If it weren't for the overrun clutch, the minute you cut the throttle, your teeth would be in the dash as the prop would act as a brake.

My first thought is that you threw out one of your fabricated plugs. Did you? Nothing else makes sense.

Mark
 
Plugs are still in. Just left the shop. The issues I described hand turning the prop clockwise and clicking and not turning counter clockwise were because the throttle was still in gear and not in neutral per talking with the tech at the marina. So what I thought was a problem was happening because I didn't know enough to go to neutral. The cause for the shut down will be determined when they pick up the boat on Monday. I will let you know. The plugged lazer11 appeared to perform much, much better than before all the prop issues started. Still would like to see 5000 to 5200 rpm or the better question is what is your opinion what should the rpm's be at full throttle. BTW the vacuum hose for speedometer is crimped therefore not giving accurate mph, will be replacing VH.
 
Forget the speedometer. If you really want to know I have a Magellan GPS I bought for $100. Per the manual, your engine is designed to run up to 5250 rpm at WOT. After 50 years of boating with all 2 cycle engines except for one, I am totally convinced that 2 cycles want to RUN. I know Mercs want to run. Proved it to myself and don't give a !@#$%% what anybody else thinks. So let that baby run and if you get above that, my opinion so be it.

I told you about the overrun clutch in F gear and that is NOT A PROBLEM. THAT IS THE WAY THE EQUIPMENT IS DESIGNED. Your money. You want to puke it for a nebulous inspection for that particular "problem", your money, your decision.
 
mark
this is where we are. the tech ran the boat around the lake, no issues turning 5200 rpm running great with the plugs in the lazer11. so with your help we corrected the original lazer 11 prop issue by installing the plugs. Now to the recent issue, you mention "if i cut the throttle" i simply dont recall if i was cutting throttle to slow down or if i was still going flat out which is what i think i was doing at the time. The motor was shaking and at that time i began to throttle down and heard the clicking and then shut it down. Because i am inexperienced and not knowing if i caused damaged or could cause further damage and just left it for a tech to check it out. so with the motor running correctly. WHAT happened on my test run to cause the problem.
 
It is normal to hear that clicking when you cut the throttle quickly !!

I would say that it depends on now quiet everything else is. When I run my heavy high pitched SS prop on my engine at low speeds I can hear the rattle. If I change props, lighter with less pitch, it doesn't rattle.

I think with the data you gave me above, you are just worrying about nothing.

If you haven't already, drain your lower unit oil. Most Mercs have a magnet on the lower (drain) screw that collects metallic particles as a normal occurrence. If yours is really covered in metal and you have changed your oil recently then you MIGHT worry.

Put in Quicksilver or Mercury Premium LU oil, made for the higher hp engines.....says so on the back of the container. WW has it with the pump, plastic tube and adapter to thread into the drain hole. I think your 115 is like my 90 with 2 vent plugs just above the AV plate, both are SS and the same size as the drain plug with a slot for a flat blade screwdriver. Remove both. With the engine vertical, insert the adapter from the new oil into the drain hole. Pump the oil into the LU till the front vent starts showing oil....pump a little more to reduce the large bubbles. Install that vent screw. Continue pumping till the same thing happens to the rear vent hole and plug it too....should have a blue gasket on each screw.

The oil you drained out should be blue black if the same oil I mentioned above. If so, fine. If yellowish, brown, chocolate or any of that, you have water intrusion into the lower unit and COULD have a problem as a result.

Do what I said and get back if a problem. If not, go out, enjoy your boat and have fun..."Don't worry, be happy" from a motion picture with Martin Downey Jr. I think.

Mark
 
Boat coming off lake to winterized and stored in 3 weeks. Will change fluids and check as you said. I had the boat running for 4 hours of fishing. She ran to 5200 rpm at 41 mph. The spedo works at high speed, but the vacume hose does have a crimp. Thanks to you I am good to go. The plugs in prop did the trick. I tend to over think, over engineer and over IBM. If there are answers, why is the prop performing now with plugs compared to prior to problem stated back in July. Oh well I will just enjoy the performance I have. Thanks much for your help.
 
Boat coming off lake to winterized and stored in 3 weeks. Will change fluids and check as you said. I had the boat running for 4 hours of fishing. She ran to 5200 rpm at 41 mph. The spedo works at high speed, but the vacume hose does have a crimp. Thanks to you I am good to go. The plugs in prop did the trick. I tend to over think, over engineer and over IBM. If there are answers, why is the prop performing now with plugs compared to prior to problem stated back in July. Oh well I will just enjoy the performance I have. Thanks much for your help.

It's really hard to figure out a problem when you are here and the problem is there. You know not of the history, nor the owner of the engine. You only know what you are told, or what you see in a picture. I do agree with over thinking problems. Some guys just like to tinker. Some like things perfect. Some don't have any mechanical moxy. Some no common sense. Sometimes you are too close to the problem. I have had that happen to me numerous times. Take someone standing off and looking at the whole picture, or not being under the stress of getting the problem fixed. They can think clearly and take things into perspective. Sometimes that helps.

Having been around machinery all my adult life of a lot of varieties, I have seen a lot and learned a lot. Having messed up things that wouldn't otherwise have been messed up; example: Accidentally breaking off a plastic vacuum hose fitting while changing spark plugs that didn't need changing on my truck once and not having a fitting and no way to go 8 miles to town to get one, I have taken the approach of "don't fix it if it ain't broke". Works for me.

I like your rpm number. Have fun and thanks for the feedback.

Mark
 
Back
Top