Mariner 30hp twin

[mister p]

I have a mariner 30hp on an Avon 4m SeaRider. It feels smooth but gutless. It is not misfiring but feels like it's not reaching it's potential. Maxes out at 17 knots two up. Am I expecting too much? Or are there another 5 or 6 knots hiding somewhere?

 

[fastjeff]

That seems a bit slow. You might have a prop pitch mismatch.

Jeff

 

[H. I. McDunnough]

Find out what the min. & max. RPMs are for your motor, ahd see where you are at.

 

[typhoon]

Is this a full on, fibreglass hull/centre console RIB? If so, they're pretty hefty things and usually deep V as well. I would expect a 30 on such a boat would be flat out hitting 20kts and would have to be on it's game to get over the hump.
So, it could need a good tune up and synch as well as a different prop. But please post your information here (prop size, max rpm).
Most all RIB's in this size range I see usually have minimum 50hp, so perhaps it's underpowered as well.

 

[mister p]

Yep, it's relatively heavy as these have twin hulls. The prop is "correct" according to manufacturer's spec for full throttle two up ribbing. The engine's been serviced, is clean and not smokey. next step will be to check rev ceilings and potential prop change. I'll keep you posted. But you're right......I was expecting a nudge under 30 knots. Let's see.