1989 60hp merc intermittent loss of rpm at higher load

[jaceheaslet]

SN: 0B399927// Baught this a few weeks ago , the first 3 times I took it out it ran like a top, after that the problem started, idles and starts just fine but when giving it gas the engine will bog down intermittently.

I rebuilt the carbs, soaked them blew them out and replaced gaskets, switched gas tanks with all new gas, new fuel filter and spark plugs, took it out again and it ran fine for 10 min then problems came back

 

[jaceheaslet]

No one with any ideas?

 

[ondarvr]

Cleaning seamed to help, clean them again, or, it could be a wire shorting out as the timing advances. More likely to be a fuel related issue though. Try squeezing the primer bulb when it starts to die, also try hitting the choke.

 

[jaceheaslet]

yea i tried sqeezing the bulb the first day, i just found a fuse housing that was pretty loose and would cut power to the other wire when jiggled slightly, going to replace that housing and try it out again

 

[jaceheaslet]

well replaced that fuse and nothing, i have noticed that when i realllly ease into it the problem will eventually go away and it planes out and stop bogging down, i was thinking the fuel pump maybe? or maybe there is a hose collapsing .......but then i figured the pumping of the bulb would rule those out......are there any kind of vacuum hoses on outboard that might have a hole in them?

 

[CharlieB]

When you cleaned and rebuilt the carbs did you notice any beads of water in the float bowls? Or signs that water had been in there, like corrosion or traces of rust in the bottom of the float bowls?

Depending on the style of carb, some have a float bowl drains. Use a suitable container and drain the bowls catching the fuel to inspect for any 'beads' of water rolling around on the ottom.

The second possibility is you may not have the idle mixtures adjusted fat enough for crisp acceleration. Two strokes rely on an overly rich idle mixture to provide the necessary additional fuel for acceleration.

Idle mixture must be adjusted with the boat IN the water and idling IN Forward gear. This provides the correct exhaust back pressure and work load. Mixture is adjusted to 'Best Idle Speed' and from there needs to be enriched even slightly more, often almost an additional one eighth turn out on each idle mixture screw.

 

[ondarvr]

yea i tried sqeezing the bulb the first day, i just found a fuse housing that was pretty loose and would cut power to the other wire when jiggled slightly, going to replace that housing and try it out again

Did you try hitting the choke? It will indicate a different issue than squeezing the bulb.

 

[jaceheaslet]

I have tried hitting the choke, i bought a fuel pump rebuild kit today and installed that and i also replaced the hosing for the gas line in the engine( the gas hose from engine to tank is still untouched) i am going to change that and actually soak the carbs all the way, when i cleaned them originally i sprayed them 4-5 times letting them soak for about 15 min each time maybe that wasn't good enough, side note.....i was out in the water and idled the engine real high for a few min and it seemed to make the problem worse i believe the engine being hotter could of made it worse? maybe not though

 

[ondarvr]

I have tried hitting the choke

What was the result?

 

[jaceheaslet]

no difference at all, im not sure it works honestly cause it starts without choke and the times it does have trouble the choke doesnt seem to help

 

[racerone]

Run with a timing light and observe behaviour of spark when motor falters.---May have to switch cylinders to check the seperate ignition systems.---A motor may have good consistent spark on one cylinder but not on one of the others.

 

[jaceheaslet]

will i be able to do that while driving it? the problem only happens while pushing the boat, it runs fine when out of the water.

 

[CharlieB]

You really need to look into the idle mixture.

Easing into the throttle slowly the air/fuel mixture stays pretty much the same so it fires evenly. It is the sudden increase in airflow when the throttle is opened rapidly at lower RPM that requires the fatter mixture to fire correctly. Above say 2500 RPM airflow is sufficient the carb is operating solely on the main jet so the problem doesn't seem to happen at all.

The electrical connection is not related at all. The electrical system is only there so you don't have to use a rope to pull start the motor.

Open each idle mixture screw just the width of the screwdriver blade slot and retest your holeshot. Repeat until all traces of misfire or bog are gone.

 

[jaceheaslet]

Thanks CharlieB i will do that next time i take it out, with the idle mixture screw in that much i cannot get it to start, can i start with it further out and then screw it in once its going? also if that is the problem why would it have all of the sudden started doing it?, the first few times i had taken it out it was fine then it started having this problem .....can the idle screw back its self out?

 

[jaceheaslet]

Also, I noticed another screw on the front of the carb but I was told this engine e didn't have high speed jets so I didn't know what it was, anyone know what these are? It's alot smaller

 

[racerone]

You lay the timing light on one of the seats.---Observe the flashing of the light when the motor acts up.-----Intermittant flashing / no light means ignition problems.-------And most carburetors do have a high speed jet.---May not be visible or adjustable by the operator / owner.

 

[jaceheaslet]

I pulled the carbs again to soak them again and noticed the bottom carb had 2 stroke oil all over it, I pre mix my gas so I'm guessing there is fuel leaking all over it, would this have anything to do with the idle needle being to far out?

 

[jaceheaslet]

Took it out today after a more thorough carb rebuild,messed with the idle screw while driving still no better, going to try the timing light next

 

[jaceheaslet]

All spark plugs did nothing less than they were supposed to , all hoses replaced btw, so right now I'm at it isn't bad gas, it isn't dirty carbs, it isn't bad fuel lines, it isn't spark plugs or spark, it isn't the exaughst gaskets, I replaced those in case water was leaking,and my buddy had a power pack and I threw it on there......anyone have any other ideas at all

 

[racerone]

Visit your local repair shop ?