1993 Evinrude 115 bogs past half throttle

[MIsteelheader]

About at my wits end with this thing...

Motor starts and idles perfectly. While throttling up, right around half throttle, motor bogs big time. Basically drops the bottom two cylinders, tested this by pulling plug wires while motor is acting up. Motor picks back up and runs perfectly if the primer bulb is pumped or fuel is sprayed directly into carb. New fuel pump installed with no significant change. Carbs have been rebuilt, checked, rechecked and then checked again for good measure. No blockages and float height is correct. All lines are brand new. Fittings and connections are either new or have been closely inspected. Tank vent is clear. Motor acts up the same on a brand new remote tank as it does on the permanent tank. Problem does not follow coils. Swapped out the powerpack with a known good one with no luck. Compression seems decent at 100 thru 115 psi.

I'm convinced that everything from the tank thru the carb is good but I still seemingly lose fuel pressure. I'm begining to suspect that it's not the fuel pump (it is BRAND new OEM) but rather a loss of pulse pressure. I figure this could be caused by a crank leak but that would cause the motor to run lean no matter how much fuel was supplied, it does not. If the crank seal ring between the bottom two cylinders is bad would that cause a reduction in pulse pressure to operate the fuel pump? If so, is there a way to measure this pulse to the fuel pump and what is the acceptable reading?

Any and all ideas and thoughts are genuinely appreciated!

 

[MIsteelheader]

Re: 1993 Evinrude 115 bogs past half throttle

I should note that there is no pulse line. The pump mounts directly to the pulse hole in the crank. However there is a pipe plug in the original pulse line fitting hole that I could tie into. Would this be an effective way to measure the pulse? If so what should that pulse measure?

 

[likitvi]

Re: 1993 Evinrude 115 bogs past half throttle

Interesting ... I have a very similar problem with a smaller outboard and I am quite confident that my solution lies in a blocked high speed orifice but I will not know that before the next spring and new season.

I looked at EPC and yours seems to be a V-4 engine with 2 double barrel carbs. When the engine bogs down, you could try to kill it instantly and then check that there is fuel in both carbs?

 

[dodgeboy1979]

Re: 1993 Evinrude 115 bogs past half throttle

have you replaced your spark plugs on the motor? i had a similar problem and replaced my primer bulb as the pump would suck it flat on me.

 

[dolla101]

Re: 1993 Evinrude 115 bogs past half throttle

i had the same problem..it was cause from a small crack in the rubber gasket in the fuel filter...rebuilt the filter and i was good to go.

 

[emdsapmgr]

Re: 1993 Evinrude 115 bogs past half throttle

If the spark is solid, it must be a fuel issue. Specifically, something related to the bottom carb, as it feeds the two lower cyls. Almost sounds as if the high speed jets are not flowing fuel/plugged. When you had the carbs down for overhaul, did you remove all the jets (esp the high speed jets in the bowl) and visually check them to be sure they were clear?

 

[MIsteelheader]

Re: 1993 Evinrude 115 bogs past half throttle

If the spark is solid, it must be a fuel issue. Specifically, something related to the bottom carb, as it feeds the two lower cyls. Almost sounds as if the high speed jets are not flowing fuel/plugged. When you had the carbs down for overhaul, did you remove all the jets (esp the high speed jets in the bowl) and visually check them to be sure they were clear?

I sure did, everything was removed blown out, visually checked and even passed thread through all jets to make sure my eyes were not deceiving me...

 

[emdsapmgr]

Re: 1993 Evinrude 115 bogs past half throttle

By any chance, do your carbs have plastic bowls?

 

[MIsteelheader]

Re: 1993 Evinrude 115 bogs past half throttle

An update... It appears as though I have found the problem. I pulled the lower carb one more time to give it another "once over", everything was good to go... While I was at it I decided to pull the fuel pump and go over it with a fine toothed comb to inspect for cracks or other defects that I may have missed. Wouldn't you know it, as I pulled the pump off the block the gasket stayed stuck to it crooked as could be! Only about 10% of the hole in the gasket overlapped with the hole in the pump/block! I must have fat fingered it upon installation. Needless to say I was/still am less than impressed with my performance on that one!!!

Gotta love lessons in humility! Goes to show you, don't overthink it (like I was doing) and exhaust and rule out all other options before jumping in too deep.

Thanks to everyone for taking the time to reply, it is greatly appreciated!

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