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Verification of cutting inout problem

R

rusirius

Contributing Member
"Well, I think I know what my

"Well, I think I know what my problem is, but wanted to run it past some other "thinkers" and see if I could get some verification.

I've had this problem since I purchased this boat towards the end of last summer. The previous owner said it had just started happening the last time or two he had taken it out, and supposedly hadn't taken any action to try to correct or diagnose it.

Anyway... This is a Johnson 30 hp 1989 outboard.

Over the winter I rebuilt the fuel pump and carb, all the general maintanece stuff, replacing gear oil, impeller, lube, plugs, etc... Thanks to the help of you folks on here, I also was able to get the sync and throttle perfect.

Anyway, so here's the problem. I start the engine and it runs perfectly. If I go at a slow speed for a while and then open up the throttle the motor starts cutting in and out. It's not surging, cause it's not a slower pulsing. Basically no matter where the throttle is past about 1/4 she won't pick up any more. For a split second it'll pick up a couple hundred RPM and then immediately drop back down.

Anything below 1/4 throttle or so and it chugs along perfectly...

Along the same lines, if I start the engine and immediately take off, it'll run a good minute or minute and a half all the way up to full throttle. Then after a minute she just immediately drops back down to that cutting in and out.

In other words, once it heats up a little it will only run up till about 1/4 throttle.

Now my thinking is that it's a problem with one of the ignition coils. I'm thinking that the heat makes the coil "fail" and stop firing one cylinder.

My reasoning for why it still runs below 1/4 throttle is that the sparks are coming much slower and the coil can "keep up" if that makes any sense?

My only other thought would be the power pack. I'm guessing it could also be the culprit. There's two reasons I'm focusing on the coils. First, they're a hell of a lot cheaper! LOL... Secondly, considering where the mount, the coils get much hotter much quicker than I would think the power pack would.

Any thoughts on this would be great. If there's a high probability of it being the power pack rather than the coils I'd rather just get it ordered and be done with it so I can get it in place to test this weekend. Otherwise if it's most likely the coils, then I'd rather just order those and go that route.

Thanks again in advance for your thoughts!"
 
"Sounds more like Your SLOW fu

"Sounds more like Your SLOW function due to overheat is cutting in. Try to disconnect the temp switch at the cylinder head and test again. If it still cuts, Your power pack is 'locked' in SLOW and must be changed."
 
"Have you changed the fuel fil

"Have you changed the fuel filters? To me, if it isn't the SLOW function, I would say it has something to do with the fuel or air. Stay cheap first."
 
"R.U.S mate, mort's on the

"R.U.S mate, mort's on the money if the motor from cold will get up and go for a few mins then starts a very sharp intermittant miss but if you slow down to around 1/4 throttle and it stops it is the slow function.

Why? 2 possibilities the engine is overheating or the temp sender is faulty, try disconecting the temp switch and water test it again."
 
"Thanks guys! I had no idea t

"Thanks guys! I had no idea this engine even had a "SLOW" feature until I just looked it up! Now that I know about it, you guys are exactly right, that sounds exactly like what it is...

So with that logic, I'm thinking one of a few things...

1 - The temp sensor is bad...
- If that were the case though, I'd think it would either "fail" closed or open wouldn't it? In other words, the SLOW either would never kick in, or would ALWAYS be kicked in... Could a failing temp sensor make it too sensitive? i.e. kicking in with a much lower temp than what it was designed?

Otherwise, the engine really is overheating... If that's the case here's the only things in my mind that could cause that to happen (assuming fuel is okay which I'm 99.999% positive it is)

2 - Impeller. The PO told me the impeller had been replaced at the beginning of that year that I bought it (last year). Because of that I never really bothered with it this year and figure it should be okay.
- I have a telltale just fine. My understanding is that as long as I have a telltale the impeller should be fine? Is that an accurate statement? Is it possible the impeller is messed up enough that I'm getting a good telltale, but not enough flow to actually cool?

3 - Thermostat. Before looking over the diagrams last night I wouldn't have even known this thing had a thermostat. Guess it makes sense. I know it's not unusual to have one fail (where it sticks) on a car, is the same true for outboards? My thought here is, if the thermostat is sticking it'd be easy to imagine the engine overheating. Is there any way to know that this is happening? I would think there would be something similar to a "telltale" for that as well, to let you know water was flowing through the actual block, not just to it?

Thanks again for all the help!!!"
 
"The limiter (SLOW) on

"The limiter (SLOW) only kicks in at aboyt 2500RPM. Less RPM, and You will not notice it, even if engine severely overheats. A temp switch may start to react at a lower temp. Way to test is to hook it to a OHM meter, 'boil' it (use a thermometer to monitor temp) ans see when it closes.
Then a few other typical 'problems' about Your engine.
1: You have what is called a UFI Power pack. That means it is mounted on the armature plate under the flywheel. Unfortunately they have a sad history of locking up the SLOW function. Even if engine cools down, the SLOW stays, so disconnect the temp switch and test. Secondly in the late 80's there were some issues and even a service bulletin where it was recommended to change the deflectors in the cooling channels surrounding the cylinders. The circulation was someway incorrect and the temp switch was set off.
I'll take Your 2 and 3 together.
Start the engine and the tell tale should be solid, and not particularly hot. Impeller is normally OK. Let the engine warm up so the thermostat starts to operate, and You will notice more and less water coming out of the exhaust relief holes at the back of the leg. (Need to run in barrel, not muffs to see). At the same time the tell tale will be slightly weaker.
The operating temp should be about 50+C, so You should be able to put Your hand on top without the smell of bacon. OMC/BRP thermostats normally don't fail 'shut', but 'open'."
 
"Thanks again! Great info!

"Thanks again! Great info!

I'll check the sensor out and see where it trips. Any idea what temp should trip it?

If the problem has to do with the cooling channels, that doesn't sound like an easy fix... Running without the temp sensor doesn't exactly sound safe either... What would be the best problem if that is it? Any ideas?

I'll check the flow from cold to warm and see what it looks like. I'm assuming you mean I need to run ON muffs not a barrel? Otherwise I wouldn't be able to see the amount of water coming out of the exhaust... ;)

As for the operating temp. Yesterday when this was happening I felt the engine. Touching the top of the head (close to the plugs) was very hot, but certainly not sizzling. In other words, I could keep my hand there for maybe a second, but it was VERY uncomfortable. Does that sound about normal?

What's the best place/way to check the actual temp. I have a heat gun. Should I just check it up at the head where I felt?"
 
"dont know about the "slow

"dont know about the "slow" issues but you should be able to lay your hand on the eng (even at the top of the heads) for 4-5 secs and not burn your self......if you have calloused hands use the back side

do you have any water coming from the exhaust relief holes?....they should trickle a lil at idle,after it warms up..."
 
"Thanks again everyone... I&#3

"Thanks again everyone... I've ordered a new switch and thermostat just to be safe... Got a new impeller too, figured I might as well cover all the bases, it was cheap enough...

I'll update this thread as soon as I have more info... I'm hoping the weather is nice on Thurs since I'm taking a vacation day... ;)"
 
"Alright guys... Here's th

"Alright guys... Here's the update...

Started pulling down this thing tonight to try to locate my problem. Figured since I ordered and received all the stuff, I might as well just swap it all and hopefully find a visible reason for the issue...

Started with the waterpump. The PO said that it was the beginning of last year when the impeller was replaced, and it would appear he was truthful. The impeller itself actually looked to be in real good shape. Blades were great and everything looked fine... Only problem I found at all was that at some point when the housing was removed a bolt must have broke off since it had a slightly larger diameter screw in one spot. I considered going ahead and re-drilling it and putting in a helicoil, but it's the middle of the night and I don't have any that size so I just stuck with what was dealt.

Next was the thermostat... Things got interesting. First, this stupid motor doesn't have a simple cover to pull off to access it... The top part of the head actually has to be removed to get to it... Not the head itself, but a rather large plate none the less with about 10+ bolts in it.

Quick back story here. The PO at some point decided to "repaint" this engine... The entire lower had been painted black, and the housing had been painted camo. (*sigh*)

The worst part is, when he painted the lower, he painted right over top of the anode. I scraped all the paint off it before I ever put it back in the water but was afraid there might already be some harm done not knowing how long ago he had painted it, but it was evident it had been a while...

Sure enough, despite my being extremely tender and using about half a can of PB Blaster, two of the bolts still wrung off before even beginning to torque on them. At least it was only two, my fear was that almost all of them would do it!

Anyway, once the plate was off and the thermostat exposed I immediately saw the problem. If I get a chance tommorow I'll try to post up a pic of the old thermostat... The thing is screwed beyond belief. I HONESTLY don't even know how this could have happened.

First off, it's not a thermostat I'm used to seeing, though maybe it's perfectly normal for this engine. To "open" the stem doesn't draw back INTO the body, but instead pushed out... The valve was on the OUTSIDE of the thermostat and pushing away caused it to open up. Again, maybe that's perfectly normal for outboards, but the new replacement I have is exactly opposite... More like every other thermostat I've ever seen...

Anywho.. The "valve" and it's stem were pushed WAY out and cocked over to one side. Spring and all were jammed way up into the opening itself along with a seal, dirt and debris, and other crap... This completely sealed off the opening except for a VERY small pinhole.

No doubt this was the cause of my overheating issue and therefore my SLOW problem.

Now a quick question... I'm going to have to drill these two broken off bolts out. I COULD just tap the drilled out holes and replace the bolts as there is plenty of room for a larger diameter hole/bolt. Is there any reason I shouldn't do this?

The other option of course is helicoils which I don't have a problem with other than their expense. Suggestions?

Last but not least... I know I've said it a lot lately, but thanks again for all the help... The advice on here has been fantastic and really helped me get through this!"
 
"That kind of thermostat appea

"That kind of thermostat appearance is not ab-normal, after a severe overheat! Probably one of the reason for repaint?
If familiar with Heli Coil I would have used that.
Did You ever run a test with the temp switch disconnected?
Use OMC/BRP sealing compound on big gasket and screw threads when reassembling."
 
R.U.S i have over the 33 years

R.U.S i have over the 33 years as a marine mechanic used a stick arc welder with stainless steel rods to build up on the broken bolt so it develops a blob which sticks out and then using vise grips to gip the broken bolt work it back and forth with crc to loosen and then unwind it.

The heat goes into the broken bolt and expands this against the corrosion which loosens it.

Trying to drill it out will have mixed results
 
"Thanks for the advice Jamie..

"Thanks for the advice Jamie... Unfortunately I didn't see the post till after the work was done...

On the bright side... She's all buttoned up and ready for testing tomorrow...

I decided to try drilling out first and figured if I screwed up and ran off I'd just drill out larger and pop a helicoil in...

I was extremely careful (i.e. measured with a caliper 6 or 7 times to find the exact center and punched it...

I have some really good drill bits I use... They punch through stainless like butter so I figured they'd be the best choice... After getting a small pilot through, I ran a 3/16" through and then followed it with a 1/4-20 tap to extract the old threads.

Maybe I got lucky, but it worked like a charm... Replaced the thermostat and gasket and popped some new bolts in and she's good to go.

So now I've got a new thermostat, new impeller (and all seals and housing), cleaned out water jackets, new temp sensor, and two new ignition coils just for good measure.

If that doesn't solve my problem I'll likely loosen up the transom bracket and dump the thing overboard! LOL"
 
"Ohh, and yeah Morton... I use

"Ohh, and yeah Morton... I use OMC gasket sealent about as much as I use oxygen.. ;) That stuff is great! I used to use Noalox on just about every bolt I put in anything, but these days I just use that sealent... I find it works fantasticly and well.. it's cheaper!"
 
"Okay guys, here we go with an

"Okay guys, here we go with another update...

I did my testing today... Not on the water unfortunately, but in a test barrel.

The good news is I THINK it's fixed my problem. Let me explain the "think" part...

I'm very good mechanically and I'm positive everything was put back perfectly. I'm still wondering if "something" is out of whack though...

When starting the engine now, I notice it seems to take a couple of seconds until I get water flowing out of the telltale... I don't know for sure if this was the case before or not... Maybe I just wasn't paying attention, but I could have sworn before it would start flow almost immediately.

Still though, it seems to have a pretty good stream, even at idle.

However... Today I kept checking the temp of the plate right where the thermostat is.

If I kept the motor in neutral and just let it idle it appeared as though everything was working fine... The temp came up to about 140 then dropped to about 120... then came back up to around 140 and seemed to stay fairly stable... I believe this indicated that the thermostat was doing it's job properly...

On the other side, if I opened the throttle up a bit (around 2000-2500rpm) it would cool down quickly and then seemed to stabilize around 120-125...

Now the bad new... Or maybe bad news... I'm not sure...

I WAS able to get it to overheat... I put it in forward gear and let it run in idle (it was turning around 580-590rpm) and the temp climbed to around 170 after 4 or 5 minutes. At this point revving to 2500 showed that the SLOW was indeed kicking in...

However, running just above idle (about 1000rpm) for about 20-25 seconds cooled things back down to around 130 and it was good to go again...

So I guess the only questions remaining are:

1) Is it normal for it to take a couple seconds to see water coming out of the telltale?

2) Is it normal for it to overheat in forward gear at very slow RPM?

Other than those two things it seemed like everything was working really well..."
 
"It may take a second o two fo

"It may take a second o two for the tell tale to start, depending on water level.
Your engine has obviously suffered from severe overheat and that might have damaged the upper water tube grommet and the deflectors in the cooling channels. Running as low as You say, will give the lowest pump capacity and any weakness in the system will be provoked.
My suggestion:
Lift off the power head and replace upper grommet and at the same time replace the deflectors. You might at the same time even want to replace the exhaust cover gaskets as that is impossible with powerhead mounted."
 
"R.U.S i would take the cylind

"R.U.S i would take the cylinder head off and check the head gasket, warpage of head etc. It is evident the engine has had an overheat at some time...the head comes off really easily.

If you find nothing then the power head would need to come off and check the water tube grommet it shouldnt be a problem with the way it sits on the water tube but you cant rule it out."
 
"Alright guys... Wanted to giv

"Alright guys... Wanted to give a last and final update on this thing...

Following the advice I got on here I went ahead and stripped down the engine.

I replaced the upper grommet. It looked to still be in good shape, but I had already ordered replacement parts and figured it could use it.

Pulled the head and replaced the water deflectors... The ones that were in there were old (original) and in pretty poor shape, but at the same time it SEEMED as though they still should have been doing their job... On a quick side note... Does anyone know why in the heck they make these? I mean why not just cast them right into the block itself???

The pistons had a fairly good carbon build up. Some de-carb spray and a lot of careful scraping took care of that. Cylinder walls looked great.

I also opened up the bypass and exhaust covers. Cleaned everything out (a little carbon on the exhaust side, clean on bypass) and replaced gaskets. Piston rings looked good and had plenty of spring... Pistons themselves looked good to...

Got it all put back together and fired it up...

This time things looked MUCH better... The entire time testing no matter what I did I couldn't get the temp above 145...

Took it out for a spin (and a fishing trip) yesterday and she purred along like a kitten... Got the boat up on plane quickly and all was right with the world... Put probably close to 2 1/2 gallons of gas through it yesterday...

I'm loving life again! Thanks again for everyone's help!!!"
 
"Hey RU,
Glad to hear you got

"Hey RU,
Glad to hear you got it working. One last thing to check.... If the S.L.O.W. was being triggered, you should have had a warning horn, and a HOT light if you have a SystemCheck gauge. Might want to make sure alarms are working properly so you'll know next time!"
 
The 30hp didnt have a systems

The 30hp didnt have a systems check gauge etc but glad to hear the engines going ok and the 145 deg is normal with a 143 degree thermo
 
"Yup, running fantastic now...

"Yup, running fantastic now... Just finished installed a set of Smart Tabs on it too... Had a stingray hydrofoil on it prior... I kept the stingray just in case I didn't like the smart tabs and just threw the stingray away after returning.. The tabs work fantastic... Jumps right up on plane now and actually picked up about 3mph on the top end... Still want to get the timing light (which is my cheap and dirty tach) on it and make sure my RPM's are getting in the right range and my prop is good, but it sounds great and I'm hitting about 25mph which I'm guessing is pretty darn good for this thing loaded up the way I have it...

Anyway, I'm stoked! Now I just gotta make more time for fishing!!!"
 
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