Stern Drive Loss of RPM

[WJorgensen]

I recently acquired a 1995 Chris Craft 187 with a 305 Mercruiser. Previously, it had not been started or ran in 3-4 years. I recently replaced the fuel pump and both fuel filters. It had a quarter of a tank full of old gas, which I added some octane booster and sea foam. I started it up in my driveway (connected to the water hose) and it seemed to run fine. I then filled the gas tank up with new gas (87 octane) and took it to the lake.
My problem: As I pin the throttle to take off, the boat seems to have little power until it reaches 2500 RPM, at which point it takes off. It takes a while for the engine to get up to speed, making it extremely hard for a slalom skier to get up.
Does anyone have any suggestions on what a solution could be?
Thank you.

 

[Talbot]

dirty carburettors and stuck floats, use some quantities of carburettor cleaner on them.

 

[Colin_S]

New set of plugs probably wouldn't go amiss either. Check the leads too. Trick I learnt from 2 stroke days was to remove plug caps from leads and snip 1/4" of lead off and refit cap.

 

[bdsweeting]

Is the prop size suitable for rapid acceleration or has it been sized for economy?

 

[WJorgensen]

The prop diameter is 14 and the pitch is 19. I don't know whether this is suited best for economy or acceleration.

 

[WJorgensen]

I used the sea foam through the carb, and I now have new plugs.
Thanks.

 

[oldsaltoz]

G'day WRJ,

Quote:
<<it had not been started or ran in 3-4 years>>

Could be low compression due to stuck or corroded rings, a compression test will give you the answer.

Avagoodweekend......