'79 Evinrude (85hp)-Engine bogging when warm & low RPM only (ISSUE FOUND) y

[CaneCutter79]

I got my motor rebuilt in Feb. of this year. It's been plauged with the same basic issue since I got it back. It could have been starting before the rebuild and to be honest, I think it was.

Motor starts fine when cold.
Motor starts fine when warm but....you MUST use fast idle to get it started.
When you use fast idle cold, the motor idles up like it supposed to. When warm, no go. There is little change in rpm and it simply won't run correctly without fast idle. It may continue to run and idle and eventually it either chokes out (makes a gasping sound as it dies) or it eventually gets better and continues to idle.

When it's bogged like this, if you engage it in gear and esentially "floor it", it will gasp and grumble a little and then take off as it should. This evening, it would bog and not get on plane until something kicked in and then it shot out of the hole like normal and took off.

Weird thing is, it runs really well at WOT. It's a 34yr old rebuilt motor on a heavy little tri-hull and I was clipping 38-40mph in choppy water this afternoon so it's running as good as it ever has.

COmpression is good too. 110psi on re-honed cylinders and 120 on resleved cylinder.

ALL of this problem is once it gets warm or when it's trying to idle. When I start the motor and back the boat off the trailer cold, it does this sometimes. It just doesn't like to run at low RPM. Anything below 800rpm and it develops this issue.

It's also getting plenty of gas because when you bump the choke on the key switch, it only makes it worse. So it's not fuel delivery. It's fuel to air mix or spark. Maybe too much fuel at low RPM? My mechanic seems to think I should change to a smaller orfice on the low RPM jet. All of the part numbers i find are only for one part with no variations for altitude. My home lake is 1,121 today above seal level and 1,118 at normal pool.


After many months of this....motor fighting me when trying to load (bogs out and dies trying to load) I'M SICK OF IT! I'm ready to get this fixed.


Where should I look? Is there a couple of electrical tests or something I can do to help find the issue?
Oh, and I've cleaned the carb. It was rebuilt as well. I've taken both carbs apart and they are clean and functioning properly.

 

[Daviet]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

You can use an inductive timing light to see all cylinders are firing when it is acting up.
What do you have the idle set at? Should be 700-750 in gear when warmed up.
Have you checked to make sure the link/sync is properly set?
Have you checked all the fuel line connections to make sure there is not an air leak somewhere?

 

[emdsapmgr]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Likely it's not firing on all 4 cyls. Weak ignition components tend to fail once the engine heats up to normal operating temps, so the timing light test is a good one. If you fine one cyl not firing, you can do a test. That engine has dual power packs. They can be swapped for testing purposes.

 

[CaneCutter79]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

What do you have the idle set at? Should be 700-750 in gear when warmed up.
Have you checked to make sure the link/sync is properly set?
Have you checked all the fuel line connections to make sure there is not an air leak somewhere?

The idle is around 700-750 in gear as mentioned.
The link/sync is set correctly (I believe, but I'll double check with my manual to make sure)
No fuel/air leaks.

As emdsapmgr said, it does have two CDI power packs. They are the aftermarket currently and I do not know the age. I've already replaced two coils in the last 3-4yrs I've had the boat.

I agree, it does seem like it could be an ignition issue. I recall the motor having these issues before the rebuild and carb rebuild so I think I can rule out the carb. I've cleaned it several times and it gets better but never fully resolved.

So if a weak iginition component, how is it that it it is not getting current at idle speeds and gets full power when the throttle is open? I have a brand new stator on the motor. It was replaced in March.

 

[CaneCutter79]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

From what I understand of the igintion system, the stator generates a lot of voltage as the flywheel spins around it with the things on the inside of the flywheel (forget the name...pickups?). The voltage generated at the stator is then sent to the power packs. The power packs then store/convert the voltage and send it to the coils on each cylinder. The coils then change the voltage somehow and send it to the spark plug.


So.

It only acts up when it's on the water. It will be really difficult to access the motor on the water unless I was to get on a sloped bank at the lake with the motor closest to the bank and work on it that way. Is that the best way to check the motor, provided I don't touch anything that could cause a severe shock!

 

[CaneCutter79]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

How To Test A Stator coil. - YouTube

I'm going to give this a try. Esentially the same theory of operation (CDI fired coils). I'm really leaning towards bad coil or pack. I'm hoping the readings will find the problem. Mechanic told me to try disconnecting the rectifier too and see if it's a bad rectifier.

 

[emdsapmgr]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

The rectifier has nothing to do with the firing of the ignition. I know you said the stator is new, but you should check the stator output at cranking rpm's. Should be at least 150 volts when measured with a special peak-reading voltmeter. There are some things which can cause low/idle rpm misfires, including a flywheel with weak magnets.

 

[CaneCutter79]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

I forget the specifics but he said something about stator converting DC to AC or something. Also he has seen where a bad stator could cause issues.

I agree about the stator. I will be checking that.

What setting do I use on m DVA? I have one (analogue) but don't know how to use it properly. I know just enough to connect leads to things with a regular volt meter.

I'm going to check with the ting light first, then coils using ohm setting on DVA and then stator. If nothing there, I'll go from there.

 

[CaneCutter79]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Here is an update. Please advise if anything seems unusual or if you have experience with this issue.

Today I changed the plugs. My last outing (yesterday), my motor ran fine during a fishing outing and then as it got hotter during the day after 8hrs of use, it hesitated getting on plane and wouldn't get past 2,500rpm. After 8-10 seconds, it would take off like normal and get on plane. I imediately felt it was a fouled plug or possibly failing ignition components.

Today I changed the plugs and the motor started and ran better than it has in a long time. Ran great actually. I gained 100rpm and another mile per hour on top end. I ran the motor for about 3-4miles, let sit for 15mins, it started great. When you slowly engage the throttle, it starts to lug and hesitate but not as bad as eariler with the old plugs. So I slowly engaged the fast idle until it would rev up past 3,000rpm and then engaged the throttle and off I went. I idled around as slow as the motor would go with the trim all the way down trying to bogg out the motor. Thing is, it ran great. Idled around 600-700rpm at 2-2.5mph. After I idled for a long time, I got on plane, ran 100yrds and tried again. Idled for about 150yds and then got on plane again and ran back to the ramp about 3-4miles away. Boat rand great. I hit 40mph easy and could hold 40mph if the chop was just right. I normally run 38 and sometimes 39.

THIS IS WHERE MY PROBLEM LIES.....

I think the boat knows when it's time to load and it doesn't want to go home! I idle through the no-wake zone and check the motor before tieing to dock. Motor is fine, a little flooded with fuel but managable. It takes me all of 3-4 mins to back my trailer down the ramp. Go to the boat, motor is bogged. Doesn't want to run past idle. People are waiting their turn so i can't check the motor for issues. I finally get it to run by easing the fast idle forward until it can reach about 2,500rpm and then I gas-it on the trottle, it chokes for a second nad then lunges forward. Carb is clear and combustion chamber is working as it should. I idle around 900rpm to the trailer and load it.

While sitting on the trailer, i use a timing light and check each plug with it bogging. Every plug is firing. I then check the temp with a laser temp gauge. 130 at the spark plug on #1 cylinder, 119 on the #3 cylinder, 130 on the #2 cylinder and 135 on the #4 (#4 is on the bottom left correct? If not, the bottom left was 135).


Here's my proposed diagnosis (PLEASE POST IF YOU AGREE/DISAGREE)
All heads were about 130 temp wise. That is TOO cold for a hot motor on 83 degree water in the summer. I think the next step up to a hotter plug will help cure my issues. I'm going to check the coil for the #3 cylinder and all others just to elimate them as failing. THen I'll check the packs, stator output, etc.

Here is a picture of the new plugs after about 8 miles of use. Does this appear to be too much carbon? Seems like it is to me.

 

[CaneCutter79]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

The rectifier has nothing to do with the firing of the ignition. I know you said the stator is new, but you should check the stator output at cranking rpm's. Should be at least 150 volts when measured with a special peak-reading voltmeter. There are some things which can cause low/idle rpm misfires, including a flywheel with weak magnets.

This is one of my next checks as well. Could be correct.


Also, what is the next step up in a hotter plug? I'm using the Champion QL77-JC6 I believe.

 

[Anchor Marine Repair LLC]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Personally, it sounds like you?re fighting on two problems.

A few things I?d like to know.
1.You said the 3 cylinders were honed, but not oversized I?m guessing?
2.4 New pistons? Any old ones? Can you prove it either way?
3.What pitch prop do you have and
4.What horse power is your boat rated for?
5.And at that pitch, what are your wide open throttle RPM?s?
6.Can you take a video of the running and when it will die?

135 optimax bad low pressure fuel pump - YouTube


A few comments on your efforts:
?A ?hotter plug? won?t change anything if that cylinder doesn?t have spark consistently. QL77JC4 is a good plug for this motor, which is in your picture.

?If you do another set of spark plug picture, label which cylinder they came out of. Also, get a good close up of the nose cone and electrode. It?s hard to make any decisions off of 2 spark plugs from a 4 cylinder motor.

?The spark plugs in the pic are very normal.

?The vast majority of V-4?s in that vintage have a 143 degree thermostat for each head. So you may have a thermostat that is stuck open or a poppet valve that is lodged open with sand pebbles. But this certainly won?t cause your dying problem.

?You can test your ignition with the boat on the trailer, backed into the lake. Just don?t float the boat as deep. I run wide open like this all the time when troubleshooting a high speed issue. Low speed is just fine too. Actually, I just put the boat in so it?s bottom is about 3 inches in the water.

?That gasping noise you describe in the first post is a lean spit. That?s not ignition related.

?The idea of a rectifier causing an ignition issue is true. If the rectifier is blown closed, so it causes a short, then the stator will overheat on the alternator side. Hot stator= high resistance=low voltage. This is a rare occurrence. The stator would have its potting dripping out melted.

The easiest diagnosis you can do is this:
Concentrate on the spark plug that looks much different than the others. So if it?s really oily black, or really clean, etc.
When the issue occurs, have your timing light hooked to that spark plug lead. See if you?re losing or keeping spark during this issue.
The next idea requires an assistant. When this bogging and dying happens on acceleration, you can substitute gas into the equation. Drill holes the size of a carb cleaner nozzle in front of each carb throat. When this problem happens, have the assistant spritz some carb cleaner into the suspect cylinder/carb.

If this gets too much for you, take it to a good marine technician who can do a leak down test on it. It?s the first place you should start, but most people don?t have leak down testers. But boy do they cut down on diagnosis time.

V-4 Leakdown Test - YouTube

 

[emdsapmgr]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

If you are not working from a factory service manual, you can get accurate ignition troubleshooting information from this website: cdielectronics.com They have good information regarding testing stators, timer bases, etc. You really need to qualify the ignition system. Once you know all the components test to normal specs, then turn your attention to the fuel side.

 

[CaneCutter79]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

If you are not working from a factory service manual, you can get accurate ignition troubleshooting information from this website: cdielectronics.com They have good information regarding testing stators, timer bases, etc. You really need to qualify the ignition system. Once you know all the components test to normal specs, then turn your attention to the fuel side.

Agreed and that's my next move. The motor is getting too much gas to it I know. If I bump the choke on the keyswitch, it makes the issue worse. It's getting spark on all 4 when the issue occurs (I have verified that) but it's not getting enough spark I guess. That or just too much fuel at idle. I may need to change my idle speed jet to a smaller jet due to my altitude. I'm at 1,118 normal pool and using a sea level jet currently.

 

[CaneCutter79]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Personally, it sounds like you’re fighting on two problems.

A few things I’d like to know.
1.You said the 3 cylinders were honed, but not oversized I’m guessing? Yes, 3 honed and 1 cylinder re-sleeve to factory bore
2.4 New pistons? Any old ones? Can you prove it either way? All new pistons (Wiseco) and yes, I've seen all 4 pistons.
3.What pitch prop do you have and
4.What horse power is your boat rated for? I have a 17 pitch 3-blade stainless steel 85hp outboard with a boat rated up to 85hp.
5.And at that pitch, what are your wide open throttle RPM’s? 5,000 normally but after the new plugs yesterday, I was running 5,1006.Can you take a video of the running and when it will die? I will try. I checked the spark on each plug when the issue was occurring with a timing light and verified spark on all four cylinders. Timing is at 4 degrees, link and sync is correct

A few comments on your efforts:
•A ‘hotter plug’ won’t change anything if that cylinder doesn’t have spark consistently. QL77JC4 is a good plug for this motor, which is in your picture.

•If you do another set of spark plug picture, label which cylinder they came out of. Also, get a good close up of the nose cone and electrode. It’s hard to make any decisions off of 2 spark plugs from a 4 cylinder motor. Will do. The 2 plugs shown above came from opposite corners because I knew the one from the bottom left cylinder (#4 I think) was the re-sleeved cylinder and running hotter than the other 3 cylinders. The #1 cylinder is shown on the right which was the coldest cylinder. That's why I only pulled those two. I later pulled the remaining plugs and they looked like the #4 cylinder's plug.

•The spark plugs in the pic are very normal.

•The vast majority of V-4’s in that vintage have a 143 degree thermostat for each head. So you may have a thermostat that is stuck open or a poppet valve that is lodged open with sand pebbles. But this certainly won’t cause your dying problem.I just recently replaced the thermostats with a full thermo kit. These are working correctly and have been tested at 140 degrees. Thus why I feel the motor is running cold and will result in excessive carbon build up. I 've already seen quite a bit of carbon built up on top of my new pistons.

•You can test your ignition with the boat on the trailer, backed into the lake. Just don’t float the boat as deep. I run wide open like this all the time when troubleshooting a high speed issue. Low speed is just fine too. Actually, I just put the boat in so it’s bottom is about 3 inches in the water.

•That gasping noise you describe in the first post is a lean spit. That’s not ignition related.It's also smoking worse than usual when spitting. I've checked for too much air, that can't be the issue unless I have a vacuum leak somewhere. COLOR]

•The idea of a rectifier causing an ignition issue is true. If the rectifier is blown closed, so it causes a short, then the stator will overheat on the alternator side. Hot stator= high resistance=low voltage. This is a rare occurrence. The stator would have its potting dripping out melted.I looked at the new stator and coils yesterday for any signs of melting or any "goo" as a result from getting too hot

The easiest diagnosis you can do is this:
Concentrate on the spark plug that looks much different than the others. So if it’s really oily black, or really clean, etc.
When the issue occurs, have your timing light hooked to that spark plug lead. See if you’re losing or keeping spark during this issue.
The next idea requires an assistant. When this bogging and dying happens on acceleration, you can substitute gas into the equation. Drill holes the size of a carb cleaner nozzle in front of each carb throat. When this problem happens, have the assistant spritz some carb cleaner into the suspect cylinder/carb. When it's bogging, if you give it more gas by using the "choke" at the key switch, it makes it worse. It's not starved for fuel. The bulb stays primed and firm.

If this gets too much for you, take it to a good marine technician who can do a leak down test on it. It’s the first place you should start, but most people don’t have leak down testers. But boy do they cut down on diagnosis time.My mechanic that rebuilt the motor is about a 4-4.5hr drive away so I've been trying to do what I can but I have not ruled out taking it to him. I have been in contact with him all summer and testing things where I can based on his requests/advise. Without having the motor in front him, it's hard for him to diagnose. He has not seen one act like this before and he specializes in these particular types of motors. He said it was uncommon issue.

 

[Anchor Marine Repair LLC]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Thanks for the detailed response.

If he honed 34 year old cylinders, that's a big part of your issue. the piston to cylinder clearance is min .004 to max .007. So if there were just the smallest cylinder scuffs, those would clean out at .002" at a minimum. Add in 34 years of wear, and you have a cylinder to piston clearance that is too much. This is being very, very conservative.

That will give you hot engine restart problems, bogging when hot, and could be hit or miss.

You have a maxed out HP rating on your boat, but you're only turning 5000 with a 17". This confirms my thoughts. A boat rated for 85 HP with a "rebuilt motor" should be swinging a 21 no problem putting you at the low end of your RPM range. A 19" would put you at 5400 roughly. A 17 on a healthy 85 in that equation would be 5800-6000 depending on the driver, weather,etc.

The one cylinder that was resleeved "is running the hottest" is actually doing the most work. It will have the best burn pattern, because that cylinder is the most efficient.

As you stated, this is very hard to do over the phone, or over the internet- accurately. So I'm going off your information

 

[CaneCutter79]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Thank you for your response. I know he (mechanic) took the motor to a marine machine shop that does all of his bore/sleeve work. They measured the bore and mic'd the cylinder walls on all 4 cylinders. He found a hole in the #4 piston which created a gouge in the cylinder wall. It was just enough that it needed a re-sleeve and it was only $50 to re-sleeve so it was a no brainer.

I can't remember the exact specs that were quoted to me but he assured me that the 3 remaining cylinders did not need a bore and that the new rings were gapped to the engine spec. If the machine shop didn't feel it needed to be re-bored, they were only turning down more work/money for themselves. He did not do the work himself, only the reassembly, etc.

I have removed the bypass cover on the #3 cylinder because the gasket was leaking. I have a photo of the rings. I'll upload. You can see the left ring has more sign of wear than the ring on the right. The piston looks brand new when rotating the flywheel. Still reads "WISECO" on the side and looks like it's never been used.

I admit, I was hoping for better compression readings after the rebuild but you have to realize.........until 3yrs ago, this motor was only used 1-2 weekends a year over the last 30yrs so it's very low hours compared to any other 34yr old V4 like it.

 

[CaneCutter79]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

I may be incorrect, he may have bored the other 3. I'll verify.

 

[wayneo99]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

you said the bypass cover was leaking? that's a problem in itself. the motor will run lean from that. make sure the cover's fingers which go into the block don't actually hit the internal casting. the thin gasket will leak, or just blow out with the compression of the motor.
don't run it like that its a lean condition

 

[CaneCutter79]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

The ring gap was .015 and indicates a "square hole" in the 3 cylinders so that's why we re-sleeved only. That and the fact that my wife would have laid a golden egg and beat me to death with it if I had spent another $300 for re-sleeving cylinders for the heck of it.

Yes, I'm replacing the gasket for the bypass cover. I just found the leak last week. It has not been leaking much if any so I know that's the no the source of my problem. It's a problem in itself that is being corrected now.

The current jet is .025 and my repair manual states to use .03 for sea level and .035 for 3,000ft above sea level. I'm right about the middle.

Can anyone definitively tell me what jet I need at 1,118ft above sea level? I'm just curious at this point.

 

[CaneCutter79]

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Re: '79 Evinrude (85hp)-Engine bogging when warm & low RPM only

Thanks for the detailed response.
You have a maxed out HP rating on your boat, but you're only turning 5000 with a 17". This confirms my thoughts. A boat rated for 85 HP with a "rebuilt motor" should be swinging a 21 no problem putting you at the low end of your RPM range. A 19" would put you at 5400 roughly. A 17 on a healthy 85 in that equation would be 5800-6000 depending on the driver, weather,etc.

Not trying to argue or disagree but you need to take into account the weight of the boat i have. It's very heavy for it's length. I think 5,000rpm is all I'm ever going to get unless I get a smaller prop.

The former owner had a 19-pitch 3-blade steel prop (factory OMC prop) on it when I got it. They tried a vented 17-pitch aluminum and they would water ski behind the boat so they used the 17 for more torque on take off.

To my knowledge, the motor has never run more than a 19 and this is a heavy little boat so that's why it's only turning 5,000 - 5,200 now with a 17 or 19. My 17 is very cupped for more bite. The 19 has little cup and it slips with full trim, creating less bow lift and a rougher ride. I got a 17 pitch Turbo prop with more cup and the ride is so much better. Having the extra cup/bow lift created a slight decrease in RPM and kept it right at 5,000rpm.

Before the cylinder went bad, I had 120psi compression on all 4 cylinders when I first go the boat. It turned 5,000rpm then and when I switched to the 17, it remained at 5,000rpm to my surprise but I got a better overall ride quality. I've since added a hydrofoil that is mounted above the prop and I get very little prop slip now. I cannot lower my motor any more on the transome and the motor shaft is just a touch too short for this transom. Without getting a 6" jackplate and lowering the motor by about 1" to gain better grip with the prop and loose the hydrofoil, it's just not worth the money for that. I'm happy with my prop/motor setup.

Again, to my knowledge, the motor has never run much over 5,000 rpm range while mounted on this boat and it's the original motor for the boat. I also tested a 21-pitch one day and it was horrible. Bad prop slip (worse than my 19) and I could barely turn 5,000. Again, this was way before my cylinder went bad 2yrs ago.