engine bogging

[curtis1979]

I have a 1980 evinrude 115. The motor will start fine and idle but rough. I did a compression test and it was 85 90 115 117. The top 2 cylinders are low. The engine sat for about 7 yrs. The issue is it will get up and go my first time I put it in the water. If I sit a minute and try to take off it wont go past 10mph. I can hit the gas lever and nothing more. No missing or anything just the same. What can it be.

 

[Barnacle_Bill]

Re: engine bogging

Do a de-carb http://forums.iboats.com/engine-frequently-asked-questions-faq/decarbing-faq-158076.html and since it sat for that long the carbs should be rebuilt and I would do the fuel pump too. The decarb just might bring those low cylinders up some.

 

[curtis1979]

Re: engine bogging

Okay I will try it and get back to you. Thanks

 

[emdsapmgr]

Re: engine bogging

Possible you are losing spark to a cyl. Weak ignition components tend to run fine when cold. Once the engine heats up to normal operating temps, it may drop a cyl. Check for spark on all 4 plugwires with an inductive timing light once it's fully warmed up.

 

[curtis1979]

Re: engine bogging

Update on this boat. I mixed up 3 gallons of gas and a can of sea foam in a separate gas tank and hit the lake. I ran a separate gas line to this tank. I was impressed. This boat ran like a new one. I put 4 new plugs in as well and I sprayed sea foam into the top 2 cylinders before I left home. The motor ran fine no bogging or loss of power. After I ran that gas out I hooked up the original line and it started acting up again. Hesitating when I gave it throttle. I hooked it back up to the other tank that was almost empty and it ran great. So my problem has to be in that fuel supply I think right?

 

[emdsapmgr]

Re: engine bogging

Any sign of water in the original tank?

 

[CaneCutter79]

Re: engine bogging

Carefull doing the decarb. I did that on my 79 model and it eventually caused problems. When a motor has not been decarbed ever or in many years, that build up can scratch the cylinder walls when it comes loose, cause rings to break, etc. Not a likely scenario but a local mechanic told me that was probably why my cylinder went down.

By the way, your compression should be closer than that. Sounds like you have sticky rings in the upper cylinders. if not, it's time for an overhaul which means you will have to resleeve or hone the cylinder walls. Mine dropped from 110 on all 4 to 110 on 3 and 65 on the bad cylinder. When the mechanic did the breakdown, the piston had a hole in it and scored the cylinder so I had to resleeve.

Oh it's definately that fuel tank. Probably water in the gas or bad fuel line. COuld be just bad gas and 7yrs old? Surely you're not running that old gas.

 

[curtis1979]

Re: engine bogging

I vacuumed all that old gas out I thought. I am gonna take the gas tank out and clean it good unless you know a better way. I will check compression again tomorrow and hopefully we have great news. Thanks

 

[willy007]

Re: engine bogging

I vacuumed all that old gas out I thought. I am gonna take the gas tank out and clean it good unless you know a better way. I will check compression again tomorrow and hopefully we have great news. Thanks

Probably a fuel line then on the bad tank

 

[willy007]

Re: engine bogging

If it's been sitting for that long a new impeller in the water pump would be a good idea

 

[MaPaHa]

Re: engine bogging

I'm a big fan of Yamaha "Ring - Free" treatment on a regular basis and it's about $50.00 per quart. You can mix it for routine maintenance with an ounce or two per 10 gallons or heavier for cleanup. It will help even out the compression if some of the rings are sticking. It's been known to help de-gum carbs also, but nothing beats a rebuild if they need it.

 

[curtis1979]

Re: engine bogging

OK I took the boat out this morning after taking out the gas tank and cleaning it very good. I put new fuel lines on and a new primer bulb. I even ordered the ring free plus and added it to the new gas. The boat started good and idled a lot smoother. No jerking like before at all. So I pushed the throttle down and it started taking off but a little slower than before. When I got to full throttle it would start acting like it was running out of fuel but tank was full. It did clear up for about 5 minutes. After that I couldn't get it to go past 1/4 throttle. Would not take gas like before. So I thought if I hooked up the separate gas tank like before when it cleared up that would work. No difference. It ran great with brand new spark plugs and a different gas tank for 4 hours. I just don't get whats wrong. The compression is back to normal at 125,122, 115, and 109. Any advice would be appreciated.

 

[curtis1979]

Re: engine bogging

Is there anyone that can help. I can't get it past 1/4 throttle.

 

[phillnjack2]

Re: engine bogging

you have dirty carbs, you need to soak them in carb cleaner overnight.

definitely seems like carb trouble to act like that.

and that compression test shows it could be time for new rings, big difference between highest and lowest numbers.
109 is very low for that motor


phill

 

[CaneCutter79]

Re: engine bogging

My motor is rebuilt from Feb this year. After break in, I get 120 on the re-sleeved cylinder and 110 on the other 3. I used to get 110 on all 4 when I got it 3-4yrs ago and its only been rebuilt once.

Having 109 doesn't seem that low to me. I have brand new rings and pistons with re-honed sleeves. As long as all cylinders are within a close percentage (10-20% i think), he should be good. I agree new rings would be a good thing but....he may not increase his compression by much if any and at a large cost unless he does the work himself and even then, its a lot of work. Most people can't or don't know enough to pull Tue crankcase, disassemble, re-ring, etc. without vast knowledge and experience.


As for your problem, I think its not the carb but an electrical issue. May be unrelated to fuel tank.

Soak the carb as suggested overnight by blowing carb clraner into the low rpm jets (4 total) and then blow air into the fuel line off the fuel pump with an air compressor. That will blow out any trash and junk that has built up. That is if you don't take the carb off and completely disassemble. These are east carbs and you can do it yourself. Take about 1-2hrs. I recommend a tear down if its sat that long. That way you can eliminate the carb as the problem.

I have a VERY similar problem with my 79 model 85hp which is essentially the same motor, just different heads and a larger bracket between the intake and crankcase. Well....the exhaust setup is a bit bigger too but that's basically the difference.

My carb was rebuilt with the motor and I have taken it apart and its clean. All parts work as designed. The motor had this issue before the rebuild and its not very consistently showing the symptoms except for bogging at idle. Could be a bad power pack or bad coil. Maybe a bad magnet on stator but I'm thinking coil or pack myself. I was told to get an inductive timing light and check each plug wire when its acting up. You just connect the timing light to a plug wire and aim the light at the floor. If its inconsistent on the flashing light....there's a problem. If not, then you need to aim at flywheel and get a bit more scientific/mechanical and mark the flywheel with top dead center and location of cylinders firing.

Also, a DVA meter to check your coils would be good.

I'm betting its electrical....

Please post an update. It may help others if you find the problem (including me).

 

[emdsapmgr]

Re: engine bogging

At 125 lbs compression, that's about factory new. The 109 compression is well below the normal 10% acceptable variance. The compression is significantly above the original compression numbers. You might want to do another decarb on the engine and see if it will come up slightly more. It bears watching. When you feel the engine start to bog, have a friend start priming the fuel hose bulb. This will force extra fuel into the carbs. See if it will run WOT as long as you constantly prime the fuel hose bulb. What happens when you quit priming it? Your fuel system may have some original rubber fuel components on it, such as hoses and the pump itself. No original rubber fuel system components were made to withstand ethanol in the fuel. The more you run it, the more original rubber components break down.

 

[CaneCutter79]

Re: engine bogging

When I took my carb apart after the rebuild to clean it (had carb problems, bowl overflow engaged), a small chunk of fuel line was the culprit. I had a small 2-3" piece of original fuel line at the fuel pump. After replacing it, I haven't had that issue.

Make sure you replaced ALL fuel line material. He is right about doing another decarb and getting that out of the system.

I'm surprised by the statement that 109 is far below the factory compression.

Isn't that due to the cylinder being out of round slightly? So small its allowing an extremely small amount of blow-by?

 

[phillnjack2]

Re: engine bogging

cane cutter
if you have a brand new sleeve and new pistons and rings and only get 120 psi then take it back as the job was done wrong.
120 is very poor for that piston, way down on what it should be (140 to 155psi ) once its run-in.

personaly i would never go near a 120psi v4 engine, i would know its clapped out.
110 on all 4 !!!!!!!!!!! how on earth did that thing start up ? thats terrible.

120 new then just gets better with running -in.. then gets a few more psi after about another 45 hours..

how can you have the same compressions after all been honed and new piston/rings ? something very wrong there.
are you sure your comp tester is ok and not sticking !!!!!!!!!!!! sounds strange.

now as for the % difference, thats only ok to have 10% difference between high and low if the numbers at high are good. and 20% is an engine that dont perform at all.
an engine could be between 90 and 95 on all 4, but that would make it a scrap engine even though the percentage is good.

i would say any v4 omc since the early 70's showing less than 125 is bad, they all should be showing mid 140's to be called good.


phill

 

[CaneCutter79]

Re: engine bogging

Sorry if I have resulted in a hi-jacked thread curtis1979. Was not my intent.

I've had the discussion about compression many times and I've never heard anyone tell me the motor could get above 125-130 new. I think my repair manual spec even indicates the motor's standard spec is 125psi compression. I'll double check that to be sure.

And it starts great. Runs like a beast too! Awesome low-end torque, quick out of the hole and good top end. Fuel economy is good too.

Update...
Yes, I checked my repair manual. For MY motor....it says, "should not be less than 100psi, the actual readings are not as important as the differences in readings when interpreting the results. A variation of more than 15psi between two cylinders indicates a problem with the lower reading cylinder, such as worn or sticking piston rings and or scored pistons or cylinders".

Not to scare anyone but my mechanic found a hole about the size of a dime in my piston on the bad cylinder. The darn motor ran great too...I didn't even loose 1mph on the top-end. You can have a motor going bad on these V4's and not know it until it's too late for repair. I caught mine just in time.

After reading the manual, I did see that I didn't have the throttle wide open during my compression testing to I'll retest per the manual. It was at idle/neutral when I performed my test.

 

[curtis1979]

Re: engine bogging

It doesn't make a difference if I prime the fuel line while driving. It still wont go wide open. I tried hitting the choke and all that did was make it almost die. I took the plug wires off one by one to see if it made a difference and the only one that didn't change was the top left side. When I took it off the engine didn't bog or anything. When I took the other three off it did bog a little. The carbs have been took apart and cleaned. I really don't know how to adjust the floats or get to them. The guy I bought this boat off of cleaned the carbs for me so he says. I just don't wanna start taking the carb apart and never get it back together right. If I had some thorough instructions I would attempt it. Thanks