I have three out of the four motors in my boat with cracked heads. I am being told that only certain castings can be used on Gem IV motors because the water passages do not match with the ones on newer heads.

your saying you have for motors in your boat or four hears on 2 motors? take off the valve covers and see what casting number your heads are. then look for the same castings so you won't have any issues?

or now would be a good time to step up the hp level by going to some high po alum casting and you might as well go thru the valve train now that you will have the heads off! just my .02

I am say i have 4 motors in my boat. It is kind of hard to find 990 castings i am trying to find out what else will work.

try tommy at choef he often has that type of stuff i bought 2 complete 454 with 990 heads from him for 400 per motor a few months back. start a thread and someone hear on the board that went to alum heads will have some laying around. this is the place to find them. you might want to post on some of the other boat sites as well. they are common enough and the hi po guys always take em off for better flowing heads. good luck, ratman

oops thats tommy at chief engines there is a link on this site for chief engines

BTW a few pics would be cool. don't see many quad engine set ups. what kind and size is your ride what drives and how many drives are you running? thx, ratman

Just little boat 1986 Cary 50

Try GM Performance parts book got mine 2 years ago from them

at least NOW we all know why there's a shortage of TRS parts