97' Ski Nautique Exhaust Manifold Replacement

[Hoagy]

I just bought a 1997 Ski Nautique (531w GT40 Pro Boss EFI) in November and it needs some TLC. I was winterizing it and had to pull the exhaust manifolds since two of the spark plugs were seized in the block.

I power washed them and soaked them in a muriatic acid bath overnight to clean the rust and gunk out of them. I don't see any obvious leaks or chucks missing, but the mating faces of the risers and manifolds aren't 100% and you can see that part of the casting has been ate away. I'm thinking although they might still last for a while, it may be a better idea to replace them now while they're already off.

Looking for suggestions whether they should be replaced or not. Also, if you're missing fins when replacing the impeller check the thermostat housing. (Really surprised this engine ran without overheating)

[NautiqueJeff]

I would go ahead and replace them. They aren't too expensive, and it is nice to not have to worry about them. Get new gaskets too, and be sure to put the gaskets on the right way.

[Jonny Quest]

It appears your 1997 may have been a victim of the dreaded "deferred maintenance" plan. You may want to dig a bit deeper and look at hoses, belts, FCC fuel filter, cables, all fluids, etc. One note...a good penetrating oil for breaking looks stuck or stubborn nuts/bolts is a 50/50 mix of acetone and ATF. Keep the storage container tightly sealed as the "magic juice" has a higher vapor pressure.

(not to bust your chops, but your engine is a 351 CID and not a 531. Too bad, as a 531 would be a beast)

JQ

[Hoagy]

Haha fat fingered it, yeah I wish it were a 531 too. We're going to take it down to the fuel injectors and get all new seals, fluids, etc, I haven't tried the acetone/ATF mix (just using penetrating oil) but one spark plug is out and the other is close. Haven't looked into how hard a project replacing the motor mounts is, but you can see a couple are damaged.