PatriYacht

Glad you found your problem. Flappers are always a good idea if you can fit them. Because you have an almost dry system, you shouldn't have reversion from the cooling water. The correct Fel-Pro is 17048. It's the same as what Jim told you but marine. The Cometic is a great gasket but almost 100.00 a piece x 4. I wouldn't use any other gasket. Even the stock Merc hp 500 gasket is inferior.

Rebel_Heart

Thanks for all of the help and ideas. I won't believe that we have found everything until I check the oil after our test run, though. You are right the cooling water is introduced so far back that reversion from that would be difficult. If I have 4 1/2 inch tails, shouldn't I just order some 4 1/2" flappers? Where should I order from? Does Trick Marine carry?

Do you think that I will have any reversion problems from the Crane cam and aluminum heads? I know that the duration is a little long on the 139651. Thanks.

PatriYacht

Should be free from reversion. I cant run flappers because I have mufflers 5+ inches dia. Every time I come off plane I think about that and try to set it down easy. You should be able to get 4.5 anywhere. Prop the boat to spin at least 5600 and you should have a rocket. A friend had a 10 meter with 600hp Banks turbo engines that went 87. You should be faster than that. Have fun.

Rebel_Heart

Patri Yacht - you had mentioned in a previous post that I should not be running the Crane cams 139651 with Dart Pro Ones (Jim V. porting) because of potential reversion problems. How will I know if this is ocurring? The engine builder was pretty set in using this cam, but I don't think that he had used with aluminum heads before. Now, I am worried about this set up.

PatriYacht

I later reread your post where you said you had long tailpipes with water injected at the ends. That is almost as good as running them dry and a lot better than stock set-ups where 4 in.rubber hose connects tailpipes to thru transom fittings. You should be good to go.