125 Force, 1986, reduced power

[sjdwallingford]

I recently purchased a 1986 18? bayliner trophy with 125 HP, and am perplexed by recent drop in power.

Boat ran fine initially, coming up to speed quickly and topping out at about 33 mph or so. Next day I took the boat out and it took awhile (30 seconds) to plane and was much slower <20mph. Also not enough power to carry speed through turn.

This is what I know: Compression good and consistent across all four cylinders. Carburetors need to be rebuilt (they leak).

My first though was that this is a carb problem. However, the fact that the power loss was so sudden, and steady?i.e., there is no sputtering or variation in motor RPM--makes me think it may be an electrical issue?e.g., perhaps a coil for a couple of cylinders went?

Would appreciate any advice. Thanks.

 

[jerryjerry05]

Re: 125 Force, 1986, reduced power

Check the entire fuel system.The fuel pump might have a bad diaphram. There might be water in the fuel.Do a spark test.
You say the carbs leak?? How bad and where?
Ethanol is reall messing with LOTS of motors.J

 

[vector4]

Re: 125 Force, 1986, reduced power

Could have lost a cylinder. When my 125 dropped a cylinder I couldn't tell except for the loss of power. Being a 2 stroke it will run smooth down 1. I was out on the water and just went to accelerate and it wouldn't go like it had about 5 minutes before. One of my CDI units was bad. You can test by pulling the plugs real quick and see if the motor tries to die. It nothing happens then that cylinder is not firing.

 

[moparman]

Re: 125 Force, 1986, reduced power

Be very careful of pulling plug wires while the motor is running , the cd units could be ruined if you don't ground the plug wires as you pull them. The voltage in the plug wires have to go some where and usually it goes back to the cd box , smoking it ,if a ground isn't supplied at the plug wire end. But pulling the wires one by one [properly grounded] is the correct way to check for a miss fire

 

[sjdwallingford]

Re: 125 Force, 1986, reduced power

Thanks Gents.

I plan I buying a spark tester and testing the spark in all four cylinders in the next night or two. This should avoid the grounding issues associated with pulling a plug wire mentioned above.

I'm thinking it's an ignition issue because the boat runs very steady at reduced power. There's no sputtering or bursts or power that you might expect if it were a fuel problem, although a fuel pump problem is something I hadnt expected. I'll report back in a day or two. Thanks again.

 

[moparman]

Re: 125 Force, 1986, reduced power

If you are losing a plug wire ,sometimes it won't show up until it has a load on it ,making it hard to find with muff's or a water barrel .You can check it with a timing light on the water though, by removing the cowling to checking each wire one by one till you find one that's missing, stopping every time to swap the timing light lead