I have 540 with Merlin block, Merlin grumpy Jenkins heads (340cc) 2.25/1.88, solid roller valvetrain. mooneyham blower with dual 1050s, EMI thunder exhaust. I am going to be getting a valve job here in the next week or so and was wondering what everyone would suggest for a cam, I know the exhaust is restrictive on these heads and I would like to go afr in the next year or two but for now I'm going to run these. My thought was that more exhaust duration might help with the exhaust flow but not sure what that will do to the power.


I bought the boat as it is and found a polylock had come loose giving me excessive lash so bad that it dinged up my roller on my lifter. I replaced it and the cam appears to be fine but still a little worried, I don't know what cam is in it I just know that it has about .650 lift. It seems that even though it has more throttle left at top speed it doesn't go past 5,600rpm. I've also only ran it on 100ll but plan on changing to 91 with torco octane booster instead, I've heard 100ll may burn too slow at high rpms so maybe that's the problem?

It might help to know the length, weight, model of boat and how you plan to use it. You may already have the best cam for your combo.

It's a 1996 25' Daytona. It just goes to Havasu pretty much. I was thinking that too just feels like it's bottle necking up top, it seems like it has plenty of carb and 10psi boost, gets up to top rpm relatively fast. I normally wouldn't want to make more than one change at a time but also don't want to waste $200+ worth of gaskets just to change it out later. Im going to pull the cam and look for numbers in about a week but that requires removing interior. I also run the timing locked at 32°

It may be the exhaust, had that happen before. More cam could make it worse. What RPM and prop are you running ?

I'm getting it up to about 5,600rpm, running a labbed 32 bravo, not sure if my drive is 1.50 or 1.36 yet, I'll turn the engine over with a bar and see if I can't find the drive ratio. I have a platinum xr/imco -0 drive and my x dimension looks like it's too low may be making it too hard for the prop to spin?

The gear ratio would help, what speed are you seeing on top ?