120 hp 1991 vro power loss.

The 120 is on a 1986 Bayliner Trophy, 17'.
The boat would run at 22 or 23 knots and was capable of 30 knots
This weekend i went out and the engin started right up first turn as always, left the dock and throtteled up and the boat would not move, I could only get 6.5 out of her.
I shut her down and restarted same problem.
I got the boat home and took the engine apart changed the fuel/water separatore, the inline fuel filter, and changed the plugs. None of the old plugs where fouled they where in decent condition maybe a little bit more oil that i would like.
I check the prop to make sure that it wasent spun but the prop held while in gear and i tried to spin it.

any idea about this sudden issue, I have been using the boat all summer and never had any motor issues.

Re: 120 hp 1991 vro power loss.

need more info about how the motor sounded, rpms are more useful than speed (knots or mph).

did you check spark? compression?

what does take the engine apart mean? did you pull off the heads?

Re: 120 hp 1991 vro power loss.

The engine idals high when in nutral, it sounds normal while running yet the boat wont plane.
the boat is trailered so it is not bottom build up.

I am new to engine work and have limmited tools, so i did not check compession or remove the heads I am trying to diagose the issue before it get to time consuming, I spend a lot of time at work and need to maximise the time i have to work on the boat.

Re: 120 hp 1991 vro power loss.

The first thing you need to do is check the spark and compression, easy and cheap to do.