Cracked Cylinder Head 92 SNOB

So it looks like I have a cracked cylinder head on my 1992 Nautique Open Bow with the 351 ford and 750 hours.

Water is leaking (sprouting out at WOT) into the bilge. There is no water getting into the cylinder, oil, etc. The engine runs great from idle to WOT.

It probably has been like this all season and maybe last year also. Not sure how it happened. The boat is winterized and stored in facility that stays 60 degrees all winter.

Some suggestions I have received are:

1. The boat runs fine, run it until it dies.
2. Replace the one head.
3. You must replace both heads at the same time to get good results.
4. Replace the whole block because after you replace the heads you will find out that you needs rings and piston work and by that time you might as well invest in the new engine given that yours is 23 years old and has 750 hours on it.

Anybody have experience with the same or similar issue?

Thanks.

Happened to my '95 GT 40 EFI.
Drill very small holes at ends of crack, Vee out crack, JB Weld. Had to reapply/add more JB Weld every year. But it lasted about 3 years for me but eventually you're going to have to replace it. Best bet would be to replace both with a set of 40 P's as regular 40's are getting hard to find plus you get a bump in performance from the P's

Here is a link that might help identify yours. You can post some pictures and maybe someone can tell too.

Paul you say GT40 heads are getting hard to find,would I be correct in assuming that all GT40s can have the same cracking issues?

Yes for marine use they are interchangeable but you have to install brass "freeze" plugs and in the case of using them on a 351 the cylinder head bolt holes need to be drilled out to 1/2" which a machine shop can do when they rebuild them or if you buy them from a supplier they can do. In this case you must change both,the P's flow that much better and they raise the compression a little. I put them on my 60's motor with no problems,but the early heads they replaced were the same volume so the CR ratio stayed the same

Also check out a Q-Bond kit,handy to have as the 2 powders work on plastic or metal, the auto trade use it alot

Good luck with the repair.

Thanks for the expensive route feedback. I looked closer at the crack. It gushes at WOT, not an issue at lower speeds or idle.

But this crack is long - over 2.5 sparkplugs and very hard to get to. JB weld isn't going to work I don't believe.

Then the cost of replace two heads is a fair amount, the incremental cost to do the block isn't going to be that much more. Especially, if if we have to start replacing parts after we did into or worse yet the season after replacing the heads. So right now I am looking for a quote to put in a new block and get the GT40P heads. That will set the boat for the next 20+ years.