1985 120hp bogging down at higher speeds

[61fish]

I have searched through the threads and cannot pinpoint my problem, so now is the time to ask for help. I have a 1985 120hp Evinrude Engine
The problem is the engine boggs out at 3/4 to full speed. My question is, why? and, Could this be related to the overheat warning horn that came on?

Here is what happened;
We were at a cabin, weeklong vacation, no problems. Thurs Pm, crusing at slow speed then sped up to about 3/4 throttle, and the warning overheat horn sounds. Within 5 - 10 sec, I slow down and shut down. Removed a bunch of weeds/grass that had covered the water intake area, sat for a bit, started up with no horn and off to the cabin we went. No problems. The next day fished in the am no problems. That afternoon tubing with the kids the engine would bog down, almost like someone had cut off the fuel supply when we were at 3/4 to full throttle. Engine died, but started right up. Ran again, reached 1/2 to 3/4 throttle and it happened again. If I backed the throttle down asap it remains running but now will begin to cut out at lower speeds. If I pull back on the throttle it will remain running. But if it dies, it is harder to start. But with the warm up lever up, it will eventually start but may die when putting it in gear.
If it sits for a while starts up fine.
I thought maybe something got into a carb bowl and would get sucked into a jet at high speed, then drop out when backing off, so I have tried two thing so far. First; pulled all carb drain screws, tilted the motor and sprayed carb cleaner into bowl, just in case. Then I also ran the boat at the lake with a different fuel tank with clean fuel. Same problem occured.
Fuel related? Electrical? Did something else get damaged when the water inlet was plugged? I have a Seloc manual which has not been much help. Your help is appreciated Thanks

 

[mrtwist02]

Re: 1985 120hp bogging down at higher speeds

Hi, Have you taken a look at the fuel filter?It might be clogged

 

[david_r]

Re: 1985 120hp bogging down at higher speeds

is she still getting hot?

is your tell-tale still pushing a good streem?

 

[61fish]

Re: 1985 120hp bogging down at higher speeds

Yes I did check and clean out the filter. The stream looks pretty good, seems to take a few seconds to get going, Im not sure it is as strong as it should be....Can this have some significance?

 

[kenmyfam]

Re: 1985 120hp bogging down at higher speeds

My tell tale is not the greatest but my head temperatures are if anything a little below normal (fractionally) therefore I know I am getting enough cooling and I either have a naturally slower tell tale or there is a partial blockage in there somewhere.

 

[Joe Reeves]

Re: 1985 120hp bogging down at higher speeds

If the fuel primer bulb has a tendency to be drawn flat, that would indicate a fuel restriction..... usually a sticking anti siphon valve (see the following).

If the flywheel on that engine has cooling holes near the outer edge of the flywheel, that indicates that the engine has a 35 ampere charging stator under the flywheel which runs extremely HOT.

The stator is a two fold component. A series of small coils pertains to the charging system. The two larger black coils at the rear of the stator pertain to the ignition system. If either of those two bllack coils start to melt down and start dripping down a substance upon the timer base and powerhead, that results in a voltage drop to the powerpack(s). You should be able to see if those coils are melting down simply by looking closely under the flywheel. Should the stator be melting down, replace it.

The stator problem usually starts out by having ignition when the engine is cold, but loses or has erratic spark when hot. Eventually there is no ignition.

(Fuel Anti Siphon Valve)
(J. Reeves)

Many of the later OMC V/6 engines incorporate a fuel restriction warning via a vacuum device attached to the powerhead. If the engine overheats, or if you have a fuel restriction, the warning is the same.... a steady constant beep.

NOTE... Only the V/6 & V/8 engines have the above "Fuel Restriction Warning". The warning horn will not sound on the other models.

The fact that a engine is not overheating, but the warning horn sounds off with a constant steady beep, and that the rpms drop drastically would indicate that the engine is starving for fuel due to a fuel restriction. Check the built in fuel tank where the rubber fuel line attaches to the tank fitting. That fitting is in all probability a "Anti Siphon" valve which is notorious for sticking in a semi closed position. It will be aluminum, about 2" long, and the insides of it will consist of a spring, a ball, and a ball seat. If this valve exists, remove it, knock out those inner components which will convert it to a straight through fitting, then re-install it. Hopefully that cures the problem.

The above procedure will cure a restriction problem with the anti siphon valve as stated. BUT, it may also allow fuel to drain backwards to the fuel tank when the engine is not running (siphoning backwards) due to the fact that the carburetors/fuel pump etc are higher than the fuel tank. This condition is not an absolute as the valves in the fuel primer bulb usually prevent this backwards siphoning problem. However.... if this does take place, the cure would be to install a new anti siphon valve.

The overheat warning horn...... Does it still beep momentarily when you turn the key to the ON position?

 

[61fish]

Re: 1985 120hp bogging down at higher speeds

Joe, There is no beep of any kind when turning the key to on. The warning horn has not sounded since cleaning the weeds off. I am going to check the stator as suugested and get back to this thread.

 

[61fish]

Re: 1985 120hp bogging down at higher speeds

Also, the tank is a two year old plastic that is back by the transom, the bulb is not drawn flat. Actually, after this happened once or twice I had someone squeeze the bulb and it was already firm. thanks

 

[61fish]

Re: 1985 120hp bogging down at higher speeds

I just came in from checking the flywheel and stator, The flywheel does not appear to have cooling holes close to the edge, and I could not see anything that resembles as if something might be melting down onto the timer base and powerhead, everything looked good and clean.
I was reading other threads regarding the "slow mode" Does this motor have that and if so what exactly is it?

 

[Joe Reeves]

Re: 1985 120hp bogging down at higher speeds

Check that warning horn. Engine NOT RUNNING, have the key in the ON position. Find the TAN overheat sensor wire that will be protruding out of the cylinder head(s), ground that wire to the powerhead.

The horn should sound. If it does not, find out why and correct that problem first.

 

[61fish]

Re: 1985 120hp bogging down at higher speeds

Joe,
I dont think I am grounding this right. I took a test light for 12 v and clipped to the flywheel and used the pointed end in the tan wire. The light lit up by no horn.. Am I grounding it right? If not what is the correct way? If so, what does this mean??

 

[61fish]

Re: 1985 120hp bogging down at higher speeds

Ok Maybe I am smarter than I thought, Actually I read a bit more. I slid the rubber down, seperated the tan wires and touched to power head, the alarm sounded. Therefore it works, Now what is next.?????

 

[Joe Reeves]

Re: 1985 120hp bogging down at higher speeds

I assume that the warning horn did beep originally when you would first turn the key on, and now it does not? If so, either the internal black ground wire has broken off of the horn, OR it is simply not grounded anymore for some reason, OR the horn is faulty. This is also assuming that the horn is a small black three (3) wire overpriced plastic horn.

The fuel primer bulb..... When the engine is running, the primer bulb (which is usually laying horizontal) does not stay full of fuel. The fuel level will drop down to the halfway point. As such, it would not feel hard/firm but rather it woukl be possible to pump it once or twice to refill it completely. Your mention of that bulb being firm when this problem surfaces brings another possibility to mind.

That fuel primer bulb has two valves, one in each end, a inlet and a outlet valve. The outlet valve (closest to the engine) can come apart at times. The inner part will float around in the bottom of the bulb for awhile BUT eventually as the engine runs, it will be drawn up back into the valve body BUT it always (due to its design) will be drawn into the valve body backwards. This effectively creates an effective shut off valve, and at a minium a very effective fuel restriction which could easily be overlooked as the restriction is on the wrong side of the primer bulb whereas it would not be drawn flat. Check that valve out.

I'm assuming that you still have good compression and spark at the momen.

 

[61fish]

Re: 1985 120hp bogging down at higher speeds

Well with help of a friend, we checked the spark and compression. The compression was 130 118 125 105. Is this a concern?
We then checked for spark; 3 of the 4 had great spark. Upper right had a very faint spark on first crank,then nothing.
We swapped plugs, then switched the coils and all worked great on three of the cylinders, with exception of the upper right. This is the orange blue wire, that is leading to the upper right coil that appears to have no spark. My manual is not clear, or I just dont understand it that well, but Im thinking this wire is coming out of the power pack????? This is a small box at the top rear of the power head. This has the following on it; CD4/8L 582530 OA 6T5
So where does this now lead me..Thanks for your help.

 

[Joe Reeves]

Re: 1985 120hp bogging down at higher speeds

There is a 25 psi difference between the highest and lowest compression reading. Yes, unfortunately that is a problem. Before throwing any money at that engine, I would suggest that you first remove the cylinder heads so that you may inspect the pistons, cylinder walls, and the underside of the cylinder heads. Let us know what you find there.

Standing in back of the engine, facing the spark plugs, the cylinders are numbered as follows

2......1

4......3

I assume that you're saying that the weak spark is with #1 cylinder (upper right).

The engine must crank over at least 300 rom in order for the stator under the flywheel to provide the proper voltage to energize the powerpack (CD4/8L).

The spark must be tested with the spark plugs removed, having a good fully charged battery, and a fast cranking engine. If you have a slow cranking engine, find out why and correct that problem, otherwise the spark test may be flawed.

Let us know what you find.

 

[61fish]

Re: 1985 120hp bogging down at higher speeds

I will try and remove the heads tonight and report back later on what I find.

In regards to the spark, yes the #1 cylinder is the one with weak, mostly no spark. The engine turned over very well, very fast, so no concerns there. All others had a very good spark.
Is that a powerpak issue?

 

[Joe Reeves]

Re: 1985 120hp bogging down at higher speeds

Did you check that fuel primer bulb valve?

 

[ezeke]

Re: 1985 120hp bogging down at higher speeds

I think that the 1985 remote control is like my 1988 in that the warning horn can only be tested at start up by inserting a spare key approximately an inch into a slot that is located just above the ignition switch under the lower aft part of the warm up lever.

The ignition key has to be in the run position and the key needs to be grounded by touching the edge of the slot.

The self testing warning horn at start up is a feature that was added later.

 

[61fish]

Re: 1985 120hp bogging down at higher speeds

Well I pulled the left head for 2 and 4 where compression was 105 in 2 and 125 in 4. I was surprised to find nothing wrong. The pistons looked great, the cylinder walls smooth, the head seemed fine and I could not find any areas in the gasket that may have been comprimised. I called a friend who is much more knowledgeable than I and he noted the only difference in the two cylinders was the lower #4 seemed to have more oil residue and actually looks to be working. It has a variation in color. The upper #2 is dry, minimal oil residue, and the color is consistent. Im not sure what this all indicates, Thoughts???

Still leaves me with no spark to #1

In regards to the primer bulb, I did not check it yet, I thought if I can take care of the compression and spark issues, I would just put a new one in.

 

[CharlieB]

Re: 1985 120hp bogging down at higher speeds

Rapair/CDI posted an excellent Ignition Troubleshooting Guide on their website, also copied somewhere here on iboats. The guide lists step-by-step directions to solve your ignition issue.

another item to check

Fuel pump flow rate, Disconnect a fuel line, direct into a can. Remover spark plugs and ground plug wires. Crank motor and observe fuel stream. should be a strong pulsed stream the diameter of the fuel line. A weak pump will not supply enough fuel for the motor to continue at WOT.