1989 Gamefisher 15 hp losing power

[Tshews]

Hello,

I have a 1989 Gamefisher 15hp outboard. Starts, runs ok. Problem I am having is after about 5 minutes on the water, I lose power. I can run about 5 minutes at full throttle and it runs great. Then I slow down and go to full throttle again and it feels as though it is running on one cylinder. I have spark, plugs are a toasted marsh mellow brown, I have compression in both cylinders, low at 62 psi but that is in both, new fuel, new CDI ignition kit, new fuel pump. I am stumped. Some one said to check the cylinder exhaust ports, could be carbon build up. Any one know where they are and how to get to them??? Any advice would be greatly appreciated. What is the gap on the plugs supposed to be? Also is there a way to check the motors rpm's? Thank you in advance.

Tim

 

[foodfisher]

Sounds like you are building a vacuum in the fuel supply system. Check for restrictions at tank, lines, connections, filters etc. Everything between tank and carb.

 

[The Force power]

As foodfisher already said "sounds like running a vacuum" check/clean the vent on the tank, maybe a collapsed fuel-line??

You can buy a tiny tach. on Fleabay for about 20 bucks.
you can get gap less spark plug or get new ones

 

[jerryjerry05]

The "exhaust ports" no way they would be a problem.
Your plugs would be carboned up and probably fouled out so bad you couldn't see the electrodes.

Foodfisher says it. There's a problem in the fuel delivery side.
Carb: float not set right, clean or rebuild.
The hoses and squeezie and any inline connectors not allowing fuel through.

To check the rpm's you'll need a tachometer.

Plugs: what's in there now?
Any idea what the model or serial# is?
They have 4 different plugs listed.
Gapless plugs, not in any parts listings I've seen??

 

[The Force power]

gap less plugs, not in any parts listings i've seen??

buzhw

 

[jerryjerry05]

Is that for a 15hp?
I know they used them in the 85/90 120/125 150