Am I running the correct prop???

planesailing · June 2016

I have a 242 with 5.7 efi merc with bravo 3. I am currently running with 2 x 24p props. My question is that my boat is a little sluggish getting on plane and only achieves around 3800-4000 rpm at WOT when underway. Usual load is around 2-4 adults, 3/4 fuel and water. I've tried various trim positions but can never get above 4000 rpm. Could a change of prop enable me to maximise the engines performance?

aero3113 · June 2016

It sounds like your not achieving your max RPM. Below is a link to your engine specifications. How long has it been since you've done a full tune up,including plug wires?

https://www.perfprotech.com/blog/tech-specs/mercruiser-v8-marine-engines-specifications

planesailing · June 2016

Boat had full service including plugs in April and had new leads, cap and rotor arm last September. Engine revs to 5000 rpm when in neutral just struggles to get over 4000 rpm when under load.

randy56 · June 2016

Did it run ok last season? something change?

planesailing · June 2016

It was running the same last season.

aero3113 · June 2016

Check you exhaust flappers. I had mine break off a few seasons ago and they were restricting exhaust flow causing loss of RPM's.

planesailing · June 2016

I can get the engine to rev to 5000 rpm in neutral though it's only underway I struggle to get to 4000.

planesailing · June 2016

That's what I thought Alswagg! What do you reccomend I put on?

reneechris14 · June 2016

24pitch on a 242 I think would be good.maybe a fuel issue,see if you can check presser under load should be 42psi I believe.

planesailing · June 2016

The engine does Rev to 5000 rpm in neutral mind. If it was s fuel pressure issue would it be the same in neutral as in gear? I will certainly check the pressure mind. Is there a fuel pressure test port on the 5.7 efi merc?!