1989 Ski Nautique 351w Hot

You lucked out with your water pressure test. Most garden hose test at close to 60 psi. Normally the high pressure from a hose will blow out water pump gaskets.
Auto systems never see more than 20 psi.
Glad you have it running again.

I did test the thermostat and it does work.

8122 - the first test was done without pressure. I let water sit in them overnight.

So far the pressure test of the exhaust manifolds look great - no leaks.

Next up, run the boat off a 5 gallon bucket. I’ll report back how that goes.

I just pressurized the engine cooling circuit and I have no leaks into the cyclinders and the engine oil remained the same, I used my garden hose at full pressure for about an hour hooked into the port side thermostat housing with the two starboard side ports plugged and the thermostat removed. I rotated the engine over multiple times by hand with the spark plugs in and out.

I’m going to pressurize the exhaust manifolds and if those check out I’m going to run the engine off of a 5 gallon bucket.

The exhaust manifolds survived the night, no leaks.

I want to pressurize the cooling circuit on the engine to see if anything leaks and then I will run it in the driveway off of the 5 gallon bucket.

I'm missing the point of what acetone has to do with leaky manifolds ? A little education please.

If you didn't find two big holes I don't think you are going to find much.

Superheated steam contracted and pulled water up over the risers.

Google is awash with hydrolock after overheat stories. Seen it a couple times myself.

SNobsessed wrote: For an easy overnight test, just prop them upright, hook hoses a couple feet long to the inlet holes, raise hoses above top of manifold, & fill them. Leave them over night & look for water on floor in the AM. RWP had 'UP' marked on top, just FYI. Have you pulled impeller back out? No vanes missing? BTW, it doesn't matter which way the vanes are when you install impeller, they will self flip.

Glad to know the PO at least says the pump has been marked "UP" on top

Just trying to see if he installed it right with the earlier questions and diagram.

I'm not sure he answered whether the pump is installed right, since he keeps talking that the impeller is installed right   

8122 - I tried a block of wood and clamps last night. I hooked my garden hose up to where the water enters the exhaust manifold. I had water squirting out from under the block of wood. I’m going to get a piece of steel, drill holes for the bolts, maybe make a new gasket, and then fill with water and air and see what happens.

What about just dumping acetone into the exhaust manifold to test for leaks? Does that work?

Keno - Yes, my impeller was installed like the picture on the left.

How do I pressure test the exhaust manifolds? Any pointers?

I don’t think I have any water in the oil. I’ll check again tonight just to be sure. I changed the oil last fall before storage.

I’m 100% positive I had the impeller going the right way. Probably should have used a new one though.

SNobsessed wrote: You drained the exh manifolds last fall, correct? Unless they both froze-cracked, it is really unlikely they both failed simultaneously.

I think you’re discounting the likelihood... with an overheat that includes lack of cooling to the exh, cracking both manifolds is not uncommon. Have seen it 2 or 3 times.

Josh - You might want to pressure test the engine cooling circuit instead. You will have to plug all the holes except for 1 which you feed 15 PSI into. I still think intake manifold.

You drained the exh manifolds last fall, correct? Unless they both froze-cracked, it is really unlikely they both failed simultaneously.

Did you perhaps run the engine from the Timmy-T before the overheat happened? Maybe you left the valve open.

Sounds good, exhaust manifolds will be coming off tonight. When I looked down into the runners, the color was rusty looking right before it goes into the head. Not sure if this is normal or not?

Took off starboard riser and it looks fine as does the exhaust manifold and the muffler. Everything looks open to me. Do I need to take off the exhaust manifolds from the heads?