1987 Yamaha 25 hp 2-stroke

SA_beef

Recruit
Joined
Aug 15, 2018
Messages
3
I am having a hard time finding a wiring diagram for my motor. Looking to run through/repair wiring under the cowl. Spark test revealed very weak spark (yellow-orange in color and little to no arch).

Thanks in advance.
 

SA_beef

Recruit
Joined
Aug 15, 2018
Messages
3
Now:

Was able to get everything wired up. Compression check shows ~125 on both cylinders and it has a good spark now. Launched it for a water test and I still have a loss of power. I cant get the boat to plane. Boat idles very well in neutral and in gear. Once I am about at half throttle the motor just falls on its face.

History of the boat:

The boat ran like a top when I was running it a month ago when i got it. I fogged the motor to decarb it and replaced a ate up fuel line from tank to motor. The next time I had it in the water it had a loss of power. It ran smooth but lost acceleration and about 6-8 mph on the top end. I noticed the fuel lines under the cowl were deteriorating so i replaced the fuel lines under the hood and the fuel pump. I cleaned the carb as well. No fuel line leaks, primer bulb stays primed. Gas tank is vented. Spark plugs brand new. So i water tested the boat again. Same thing with loss of acceleration and power. After a little while i thought maybe the carb throat cover plate was choking the motor. i pulled it and i was getting the original performance - quick and fast. Dropped my buddy off on the bank to clock the speed and without cutting the motor off i backed off the bank, put it in gear and accelerated. Only for the motor to fall back on its face. Like its stuck and cant plane.
 

robert graham

Admiral
Joined
Apr 16, 2009
Messages
6,908
Maybe deteriorating fuel lines has caused very fine particles of rubber to enter and foul your carb?....Drain carb/carbs with small drain plus unto a clean white rag to inspect for particles or other matter that might plug a jet
 
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