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Alpha I leg stealing power?

scheffer said:
5) 5 days later on Sunday, took the boat out with family, noticed problem planing.
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The extra weight in the boat with the family + now a full fuel tank will cause the boat to run the way it is now, Keep in mind your comparing how the boat ran with just you in the boat after the service with less fuel.

How big is the family?

Does this boat have a water tank for a sink, Head, etc? if so did you put in water the tank for the family to use?

I would suggest that you go run the boat with just you in it again and see if you get a change for the better in the running attitude of the boat.

Good luck.;):)
 
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Master mechanic said:
List of possible causes of low WOT (Wide Open Throttle) rpm.
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If you read the OP's first post, he describes his boat as a 2005 Bayliner 245 with Mercruiser 5.0L and Alpha I drive.

He also describes that his previous planing speed could be obtained at 3.1k to 3.3k rpm that particular day!
He doesn't mention the planing speed, he just mentions the rpm.

After this mechanical work, he now must reach 3.8k rpm to achieve planing.
(we must assume that he means the same planing attitude as before)

In later posts, he says that no other changes were made to anything, he's using his TT's and drive trim, etc.
His hull is clean, drive is the same drive, prop is same prop,etc..... so no changes here!
No engine work had been done either.

However, in post 28, he's now referring to it as "Loss of Power", whereas earlier it was "More RPM to achieve planing attitude."
So I'm a bit confused on this, as you guys may be.

He now also notes that 40 gallons of fuel was added..... 40 gallons = a conservative 240 lb.
5 days later he takes the boat out with his family.
Agree..... what does a family weigh?????
Mom........ 125 lb. ???
Kids....... 80-100 lb. each????
Misc gear ........ 50 lb. ???
240 + 125 + 160/200 + 50 = 575/625 lb. + or - a bit!

Where was this weight placed???


So what I get from reading this thread, is several things:

1... he has no idea what his WOT RPM was or is.... he never bothered to test this.
For any boat owner, this information is a "MUST", IMO.

2... his compliant is the increase in RPM that is now necessary to achieve the same planing attitude.

3... since he is able to increase RPM, nothing to me suggests an engine or engine tune issue.

4.... he may not be considering this added weight from when he noticed that his previous planing speed could be achieved at 3.1k to 3.3k rpm.


Scheffer, not beating you up here, but if you were to look back through your thread, you may see that you have somewhat "piece-mealed" the information out to us.
Had this all been available from post #1, it sure would have been easier!

I'm now thinking that it's very possible that your difference is simply in the way that the boat was loaded in each scenario.

.
 
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Hi Rick,

Agreed, I have been a bit piece-meal with the data. I have to apologize for that. I'm fairly new to power boating so a lot of things are new to me...

I was trying to keep the original post "condensed" to make it more readable (obviously, a mistake)... Also, up until the first few replies, the ONLY thing that I had considered that I "changed" was the leg maintenance. Once someone suggested other things like gas/bottom/etc, I realized that there was more than one variable in my situation.

As you pointed out, in my original post, I said that it requires more RPM to stay on the plane. Later, I said that I had less power. I didn't mean to be confusing with this. In my brain understood the two statements to be equivalent. My reasoning: My limited understanding of engines (which could be flawed) says that higher RPM = more power output to prop. Therefore, if I used to be able to plane at ~3.2k but now I can't, then there must be less power available to the prop at 3.2k RPM. Also, if now I need 3.8k to just stay on the plane, then now there must be the same power at 3.8k RPM that I used to have at 3.2K.

So, I'm looking for reasons that now after service and gas, it takes more RPMs to make equivalent power... Feel free to correct me if my understanding is flawed...

As to the weight increase on the Sunday... I'm not positive you aren't right, but my gut says this isn't the issue. First, one correction. I bought the gas on the way home from the marina with the lift. I had to motor for ~45min with this additional fuel and didn't notice a problem planing. So, the increase in weight between no problem and problem was just the family and snacks. My wife is ~125lbs as you guessed (good one), but my 2 kids are both under 5 so the total for them is less than 100lbs (snacks included). All other gear was equivalent (no extra water or what have you was added) So, the weight difference before and after the problem is less than 250lbs.

From my experience (which is limited), weight hasn't made a significant difference to the boats performance. I have had between 1 and 5 adults (say 200 -> 1000lbs) on the boat and I've always been able to plane at between 3.1K and 3.3K RPM. So, I'm not sure how the small difference of the family could cause this much difference in performance?

Just to satisfy my curiosity.... can you explain why you don't think it could be the gas? Assuming there could be either water in the gas, or gunk, or just lower octane?

Continued thanks for putting up with me..
 
scheffer said:
Hi Rick,

1.... Agreed, I have been a bit piece-meal with the data. I have to apologize for that. I'm fairly new to power boating so a lot of things are new to me...

2.... I was trying to keep the original post "condensed" to make it more readable (obviously, a mistake)... Also, up until the first few replies, the ONLY thing that I had considered that I "changed" was the leg maintenance. Once someone suggested other things like gas/bottom/etc, I realized that there was more than one variable in my situation.

3... As you pointed out, in my original post, I said that it requires more RPM to stay on the plane. Later, I said that I had less power. I didn't mean to be confusing with this. In my brain understood the two statements to be equivalent. My reasoning: My limited understanding of engines (which could be flawed) says that higher RPM = more power output to prop. Therefore, if I used to be able to plane at ~3.2k but now I can't, then there must be less power available to the prop at 3.2k RPM. Also, if now I need 3.8k to just stay on the plane, then now there must be the same power at 3.8k RPM that I used to have at 3.2K.

4..... So, I'm looking for reasons that now after service and gas, it takes more RPMs to make equivalent power... Feel free to correct me if my understanding is flawed...

5.... As to the weight increase on the Sunday... I'm not positive you aren't right, but my gut says this isn't the issue. First, one correction. I bought the gas on the way home from the marina with the lift. I had to motor for ~45min with this additional fuel and didn't notice a problem planing. So, the increase in weight between no problem and problem was just the family and snacks. My wife is ~125lbs as you guessed (good one), but my 2 kids are both under 5 so the total for them is less than 100lbs (snacks included). All other gear was equivalent (no extra water or what have you was added) So, the weight difference before and after the problem is less than 250lbs.

6.... From my experience (which is limited), weight hasn't made a significant difference to the boats performance. I have had between 1 and 5 adults (say 200 -> 1000lbs) on the boat and I've always been able to plane at between 3.1K and 3.3K RPM. So, I'm not sure how the small difference of the family could cause this much difference in performance?

7.... Just to satisfy my curiosity.... can you explain why you don't think it could be the gas? Assuming there could be either water in the gas, or gunk, or just lower octane?

Continued thanks for putting up with me..
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1.... Understood!

2.... actually, this is often a result of an onlooker not reading or understanding the entire scenario. I read the RPM issue, and saw that as your main concern at that point.

3... for me, the ability to increase RPM, initially eliminated the idea of an engine issue. But more info was needed, IMO.

4.... the logical reason would be more weight in the hull from when you were noting the RPM before.

5... I suppose you need to consider how the weight was distributed.
Stern heavy hulls, resist planing.

6... Yes...... it makes a huge difference on your hull with only 5.0L engine power. Add to this the single prop A drive.
Perhaps you have not noticed this in the past.

7... Well, as siad, I've based this on the ability of the engine to increase RPM.
Had you NOT been able to increase RPM, I may have gone in another direction.


All of our suggestions are offered without the ability of being there with "Hands-On" assessment.
Add to this you being new at power boating, and you can see that right off the bat, we all have a disadvantage.
No harm/no foul, but certainly not ideal in order to effectively help you touble shoot.

.
 
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Sheffer:

You have heard from the best (me excluded) about the RPM issue. Is it real or perceived? We don't know but you say it is so help us help you fix it. Have you opened the engine cover for a quick once over? In order to remove the OD a safety minded mech. would disconnect the battery neg. cable or activate the emergency "man over board switch" to disable the starter.

Since the OD was removed perhaps the mech. had his hands on the shift and throttle cables. Check the throttle to see if it is allowing the carb WOT. Some people will put their hands on anything (top of the carb spark arrestor is a common point) in a moment to steady themselves while tring to stand on their heads to do something in a cramped engine bay. Been there and done that...sold my I/O since I could no longer stand on my head and bought an outboard.
 
OK, someone noted that his motor comes up as a 5 litre with throttle body injection which I agree would be 220 hp. BUT if you doubters about 260 hp 5 litre motors do some checking you will find that the 5 litre also comes with multiport fuel injection and is rated at 260 hp. A large percentage of newer (2005 and up ) bayliner boats similar to Sheffer`s boat, came with the 260 hp motor. His apparently did not !
 
Now, back to his perceived problem. IF he is correct and the boat now takes more rpm to get on plane then I can`t see why some are calling this a loss of power.
Something is causing the boat to require more push from the motor to get and stay on plane.
Some causes could be improperly trimmed leg. If the leg is trimmed too low it would be plowing or pushing water with the bow. The opposite can also be true.
On my 24 foot and considerably heavier fibreform if I trim my leg up to get better cruising speed at slightly lower rpm but I stop for some reason I have to trim back down to take off and get on plane quickly. If I don`t , my boat will stick it`s nose in the air and refuse to come up on plane.
Next thing to consider, does he have trim tabs. I do and I can drop them down and this will push the nose of the boat down into a plowing attitude and pull me right off plane.
All I`m saying is, the motor didn`t change just because the leg was removed and reinstalled.
The thing I`d be more interested in is ,has the boat speed changed to maintain planing? Or has something changed that now requires more rpm to get the required speed for planing?
Too many variables hare and not enough info to diagnose his problem but my feeling is, it something other than engine performance.
 
despy said:
1... Hard to believe that with all the knowledgeable people on this forum, so few are aware that the mpi version of the 5 litre engine in 2005 and up is rated at 260 hp and a large percentage of bayliners used it in their 24 foot boats.
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1... and your points in the above that relate to Scheffer's issue is?????? :)
No offense, just trying to learn what this means for us!

despy said:
.............
1... if I`m not mistaken, the 5 litre in 2005 was rated a 260 hp which is same as older 5.7.
Should get that boat on plane with no problem. If it is taking considerably more rpm to get it on plane, then something has to be slipping or leg is trimmed too high or tach is simply gone wonkie.
2..... Fact is, his symptons aren`t power loss as much as asking why the motor APPEARS to be reving higher to do the same job.
3..... Better question to ask might be what SPEED he used to plane at and what speed he needs now.
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1 for both above..... Despy, I appreciate your pointing that out, but I think that the engine horse power (be it 220 or 260.... TBI or MPI), is a moot point considering the issue described. You yourself elude to this in post # 13 and again in post #39!
Just curious!

2 & 3..... Bingo! :)

See Bill's response post #10.



Also, some the questions that are now being asked, have pretty much been discussed....... and from what I read (post # 17), he IS using both his TT's and PT.


Post # 20 confirms that this is the original drive and propeller.

Post # 23 confirms NO Growth on the hull!


A member from another forum has been quoted in post # 26.
Items # 2, 5, 6 and 12 make some sense..... the rest do not necessarily apply.


Post # 27 suggests to check the propeller.
Post # 28 suggests no prop damage.


Post # 32 makes darn good sense, IMO.


Perhaps re-read posts # 34, 35 and 36!



If this is not hull growth, tachometer, and/or added weight related......, I'm somewhat stumped.

.
 
I would look close at the flame arrestor (air cleaner) and make sure it is clean. If dirty wipe off with clean rag........

also you say the prop is good, what about the plastic hub? is it in good shape or twisted in any way. Maybe your mechanic while removing/installing the outdrive dropped it and damaged the plastic hub??? Just a shot in the dark.......

The issue described sound like loss of propulsion so what is causing this.

Lack of clean air, lack of a clean prop ie: blades clean and no rough surfaces, cupped. Is the prop a new or rebiult prop? Rebiults typically have no cupping and are you 100% sure the prop is the same as the one (meaning identical and not the same pitch but a different prop) that was on it before and after servicing?


One other question. do you have hudraulic trim tabs?

If so did they get moved up or down since last use?? they will reak havvoc with planing off if in the wrong positon??

Just some thoughts on this reaaaaaalllll long thread...............lol
 
Hi Everyone,

I need to get down to the boat and try some of the suggestions (e.g. going back out by myself with a light load, check plugs, tach, more trim experiments, etc). However, I really really don't think these things are the problem. I'd never had any problem planing with heavy vs light load before. The trim tabs/leg trim do make a difference, but I've generally found that the difference is in the speed of the boat, not in it's ability to plane. The plugs/tach/throttle cables going bad at EXACTLY the same time as the maintenance without anyone really getting into the engine compartment just seems like too much of a coincedence to me. Anyway, this is not to say that I should check/try all these things, but they just seem a bit unlikely in my new-bie mind.

The one thing that does ring true to me is that I bought gas directly after the leg service... I feel like this important snippet of info is getting lost in the thread somehow. I realize I don't have a much experience with engine tuning/troubleshooting, but it seems like the quality and condition of the gas put in a motor must have a big impact on that engines performance... otherwise, top-fuel dragsters would just use good old regular gas from the corner station ;)

5 minutes after putting the boat in the water for the leg maintenance, I filled up with gas from a fuel dock I'd never been to before. It seems like if there was a problem with this gas (dirty/water/low octane) it would adversly affect the performance of my engine. Can someone please help me understand what the effect of bad gas could be on an engine? Also, if you are convinced this is NOT the source of the problem, help me understand why you think that...
 
Because you were able to achieve a Higher RPM with the same propeller and same drive ratio.
Add engine trouble into the mix (poor fuel, etc), and the RPM most likely will NOT increase... if anything, it will be decreased!

Unload the firewood from your truck, and it will go faster up a hill, for example.
If you were to look at the truck's tachometer, you will likely see an increase in RPM from where it was previously with the firewood loaded.
Put the firewood back in, and do the same test.

You could simulate this test by also changing gear ratios.
 
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The one thing that does ring true to me is that I bought gas directly after the leg service... I feel like this important snippet of info is getting lost in the thread somehow. I realize I don't have a much experience with engine tuning/troubleshooting, but it seems like the quality and condition of the gas put in a motor must have a big impact on that engines performance... otherwise, top-fuel dragsters would just use good old regular gas from the corner station

5 minutes after putting the boat in the water for the leg maintenance, I filled up with gas from a fuel dock I'd never been to before. It seems like if there was a problem with this gas (dirty/water/low octane) it would adversly affect the performance of my engine. Can someone please help me understand what the effect of bad gas could be on an engine? Also, if you are convinced this is NOT the source of the problem, help me understand why you think that...
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Ayuh,.... As Rick, 'n several others keep tellin' ya,...
Bad gas would cause a Loss of rpms...
Not a loss of Speed, 'n Higher rpms...

If it takes 700 More rpms to do the same speed, yer draggin' something that's causing a need of more horsepower to move the load at the same speed...

Bad gas, or low octane Ain't the issue, as explained by yerself here...
 
Any time I drive a boat with trim tabs including my own, starting out tabs are down and drive is ALL THE WAY IN ( or lowered all the way down). Then when on plane, bow comes down, tabs are raised where they need to be and when I get going over say 40mph or so I will just raise the outdrive a bump to find the sweet spot but not much.

Question, could his O/D been reinstalled not all the way in or down causing a loss of power or technically torque?
like somebody trying to get on plane with the outdrive not all the way down?
 
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One more stab, and then I'll leave this alone until I can get down to the boat and run some of the suggested experiments...

Here is a hopefully better description of how I get the boat out of the hole and onto plane as well as what's causing me concern (before and after)...

Before:
- boat is off plane with throttle just a bit past idle (slowly going out of marina for example)
- once the boat is out in the bay past the slow area, push throttle to WOT
- wait for boat to get on plane, RPMs rise up to ~4K, speed up to about 23-24knots (if I leave it WOT, boat will continue to speed up)
- pull back on throttle until RPMs are at 3.2-3.3K, speed reduces to 19-21knots depending on load and trim position
- boat maintains comfortable plane and cruises nicely

After:
- boat is off plane with throttle just a bit past idle (slowly going out of marina for example)
- once the boat is out in the bay past the slow area, push throttle to WOT
- wait for boat to get on plane, RPMs rise up to ~4K, speed up to about 23-24knots
- pull back on throttle until RPMs are at 3.2-3.3K, speed reduces to 19-21knots
- RPMs continue to reduce and boat gets slower and slower as it falls off plane, RPMs continue to decrease as speed slows more and more (I don't know what happens if I just leave it here for a long time)
- push throttle back to WOT
- wait for boat to get on plane, RPMs rise up to ~4K, speed up to about 23-24knots- pull throttle back "less" to keep RPMs at 3.8K boat maintains plane (I'll have to go back and try this to find out how fast I'm going now, but I'm certain its faster than the previous 19-21knots planing speed)

In my mind, this implies a loss of power at a given RPM. If I could plane before at 3.2K and it took 100 units of power. Then if I can't plane now at 3.2K RPM, it implies that my engine is no longer outputting 100units of power at 3.2K RPM. No? Am I still out to lunch? It seems like this is the same situation as the truck with 700lbs of logs in the back.

Like I said, if everyone still agrees I'm "on glue" I'll go run some more water tests, etc and try to get more meaningful data...

Continued thanks for all your patience... as before, still greatly appreciated.
 
OK, I am backing out of this one as the problem has changed from needing more rpms to plane to now loosing rpm and dropping off plane.
The key phrase in the above post is "rpms continue to reduce''
 
despy said:
OK, I am backing out of this one as the problem has changed from needing more rpms to plane to now loosing rpm and dropping off plane.
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I must agree! I'm out until this one gets back on track!
Continued "piece mealing" isn't helping anyone! All of this could have been explained in post one!

.
 
I got the answer...

Normally you are going with the tide. This one time you were running against it.......


Sound good?

Next.
 
gl115 said:
Question, could his O/D been reinstalled not all the way in or down causing a loss of power or technically torque?
like somebody trying to get on plane with the outdrive not all the way down?
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Yes I believe so, But honestly i'm not 100 % sure if this idea would affect the running attitude of the boat or not but i suppose it could.

If his boat mechanic installed the trim cylinder connecting rod ends 180 degrees out of specifications from the book, then maybe it could affect the boats performance like this. I just haven't experienced it myself to really know, Maybe someone else here has? My thinking is, if they are 180 out then maybe it could have changed the trim angle just a little bit? Any and all opinions are welcome.:)

For those who are interested in the correct procedure of installing the trim rams on an alpha drive, See the top of page 5B-14.
http://www.boatfix.com/merc/Servmanl/14/14b5.pdf

kghost said:
Normally you are going with the tide. This one time you were running against it.......
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This was one of my thoughts as well, Water conditions would definitely make the boat run like this, along with the added weight in the boat.;)

I'm sure this happens consistently for the people that run boats every single day for a living.

Another thought would be if his throttle lever was retracting on it's own without him noticing.

And one other least likely thought would be, Depending on how the boat was sitting on the lift during the service, maybe it could have changed the boats hull bottom just enough to put a small hook in it.

Docksidemarineservices said:
Lots of energy spent on this problem with very little diagnostic time.
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Ah, That's what makes this fun especially since we're nearin winter time now, lol.:p:)
 
I noticed earlier he stated he hadn't bothered in the engine compartment. Has it rained? Sounds like you have taken on water. Mabey the lead was disconnected by accident when your mechanic disconnected the battery. Who knows, even if it didn't rain the repair could have caused a leak to start in the transum. Hope she's still above water when you return.
 
RicardoMarine said:
I must agree! I'm out until this one gets back on track!
Continued "piece mealing" isn't helping anyone! All of this could have been explained in post one!
.
Click to expand...

How do you suggest I get it back on track?

I didn't intend to frustrate people or confuse the issue although it's seems that's what I've done. Perhaps if I had more engine experience I'd have explained the issue better at the start, but it's taken some of your responses for me to see what details are important and what details I missed describing... at any rate, we are where we are... is this a lost cause or do you have a suggestion on how to keep moving forward?
 
I`m not trying to be sarcastic so please don`t take any of this wrong.
You have not been totally clear on exactly what the symptoms are.
You seem convinced it has something to do with the gas you bought.If you are, then the best way to find out is to find a different source of gas to run the boat on to see if that is the problem. You`ll have to ask here what method to use as I am not sure how you would hook up a different source such as a day tank from an outboard, but I`m sure someone here can help with that. Be aware that there is a safe way to do it and other ways that could be a fire hazard.
That being said, after reading thru this thread, I fail to see how the gas would cause the problems you appear to have. Bad gas won`t make you have to rev the motor higher to get on plane and won`t cause the motor to lose rpm and fall off of plane.
Bad gas will make it run like crap or not at all if there is a major amount of water in it. You say it takes 3800 rpm to get on plane. I doubt it would turn 3800 rpm "under load "if the gas was bad.
My best advice at this time is to forget everything typed on this thread so far and start over by telling us exactly what the boat is doing different than before.
 
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