new guy here so sorry if this is the wrong place for this... no stranger here to boats or motor builds but new to Formula boats and boat motor builds... wondering what people are running for there 502 cam. pretty basic setup. i have 2 new gen VI 502's going to possibly change out the pistons and cam. curious what others have done. down the road ill most likely build the motors but not for a couple years probably.

The biggest thing I would say that is different with boat engines and wet exhaust is too much overlap will cause water reversion which is no beuno. In a very generic sense, 112-114 LCA on the cam is about as tight as you want without worry or some other mods to prevent reversion. To answer your question though, a lot of people have run the 500 EFI cam or Crane '731' ... if you have carbs it may be more straightforward or easier to compensate for the new cam ... if you have MPIs, I would do a search; you'll see that a lot of people come to the realization that the MPI intake is a limfac (and obviously logs too) -- you'll likely need some ECU programming to optimize for your mods which is not available in popular programs like HP Tuners. Instead, MEFI Burn seems to be the most popular, but there are several folks that have some canned tunes/setups that can help.

You mentioned 'no stranger to boats' but it bears repeating that if you are changing pistons and likely CR, keep in mind where you intend to fuel the boat ... 'cause higher octane fuel is not as prevalent on the water.

Good luck ... we have a '99 Donzi with two 502 MPIs and I have been itching for some mods just not in the cards right now.

Corey

You can't upgrade the cams unless your exhaust has long risers. A good exhaust system is needed for any upgrades.

good info! I’ve been doing a bunch of research on this reversion voodoo haha, I’ll be making sure to keep my compression around 12.5-13 so I don’t need fancy fuel, San Juan’s have 92 on fuel dock so safe there. I’ll be running the holly sniper 550 most likely but still thumbing threw the options... thanks!


yes sir absolutely will be upgrading exhaust, I failed to mention that part

Compression around 12.5 to 13 with 92?? If using iron heads, I wouldn’t do more than 9:1.

We’re you meaning air/fuel ratio?

Ya your absolutely correct, I wrote that half asleep last night, my mistake

Why replace pistons on new engines then ?

To get the compression to 13-1......

He needs a Domed My Pillow.

May not change pistons, depends on what I find when I open it up, will probably do a cam but maybe the one that’s in there is fine, won’t know till I open her was just wondering what the 502 guys/gals are running for a cam