Bob Madera has often mentioned guys looking for a lopier idle when they ask for cam advice from him, and his advice to them is to forget about the idle and use the cam that is best suited for how the boat will be used. If you want a big, mean sounding cam, you will most likely have to spend a few grand for exhaust that mixes the water into the exhaust stream at or near the transom, otherwise you will likely suck water back into the engine and eventually kill it. Even then, without upgrading the other components to take advantage of the cam timing (heads, intake, carb, compression), you will probably not see any significant power gains, and may actually go backwards.

My advice would be to leave it alone and enjoy the boat like it is. The guy with the mean sounding, lopey cam in his boat probably spends a lot of his time wrenching on it to keep it running. Either that, or he has the disposable income to pay someone else who knows what they are doing to wrench on the boat for him. Ask me how I know this. :rolleyes:

The truth hurts sometimes...

Yes this is VERY true! I'm running some of the best headers from back in the 90's. when they were 6500$ from Stellings. My cam specs are custom comps cam solid roller .693/.695 @.50 on a 104 LSA. My is very
Ignorant when docking but thanks to patients and good tuning skills. We have made it easier. After a rebuild due to low oil pressure I've found my lifters are now bad (light grind in bearings). It cost lots of $ to sound good but perform good as well. Although you can go slightly larger then what you do now (cam wise) IMO but not overkill as it will hurt performance. And the addition of other parts to make the cam work. Everything must "match".

When I had my 496 Mags converted to HOs, the lope at idle sounded much better (to me). That was simply an HO cam and a reflash of the ECM. I would think you could do something similar to a 502. Of course, I'm no gearhead.

what exhaust would be the ticket... guess I should start there and work my way into the motor

Seeing that you want to run a big cam look for either Gil or Stainless marine manifolds that are dry to the tip. Plan on spending between $900-1500, stainless marine will be the better more expensive option. However remember this, a lopey cam is going to want to make it's power up high in the RPM range. Which means everything in your engine is going to have to be upgraded. Better rod bolts, valve springs, retainers, your going to need the best roller lifters (morel), higher compression pistons, upgrade your Merc carb, ect. As others have said, it's not as easy as just throwing in a big cam to sound cool. Get in touch with Bob from Marine Kinetics and design your engine right. Otherwise your just going to be wasting money.