Confused about cooling on my 87 cobra?

I purchased an 87 smoker-craft Avanti 19', and have been working on replacing the stringers and deck. Yesterday for motivation, I broke out the muffs to start the engine to help build my motivation back up!

When I purchased the boat we used the muffs in his driveway, and water seemed to be flowing from the prop freely without a problem. I started the boat up, and didn't notice any water coming from the prop, so I chalked it up at first as the thermostat didn't open up and let any water out. The temp climbed to about 220 and stayed there. It never got any hotter, I did keep it running for about 2 minutes after the temp leveled out, and then shut it down because I was concerned. Even after the temp leveled off at the 220 degrees-F, I still did not see any water coming out anywhere on the outdrive, just exhaust and steam.

So, I guess my question is did I not leave it running long enough? Or do I need to look at something else? I did pull the cover off of the drive and pulled the impeller housing off, and inspected the impeller and it is soft and supple with no cracking or tears and seems to be in good general condition. I also bumped the engine over to ensure the shaft was turning, and it was. When the engine was being turned over with the impeller housing off water came out of the port on the left side, not much but some (left side standing at the back looking towards the front of the boat).

The boat is an 87 smoker-craft with the OMC 4.3 V-6.

Re: Confused about cooling on my 87 cobra?

Did you have the drive all the way down when you ran it?

Re: Confused about cooling on my 87 cobra?

Just an FYI, even with the thermostat shut water should still be flowing, there is a bypass in the t-stat housing that lets water by so the exhaust manifolds stay cooled when the thermostat is closed.

Re: Confused about cooling on my 87 cobra?

I didn't have it have it all the way down, I was limited on room since I did it in the garage. I had a big water trough under it to catch the water.

Re: Confused about cooling on my 87 cobra?

Have you checked/replaced the impeller? 220? is way to hot for a marine engine, you shouldn't see over 160? on muffs.

Re: Confused about cooling on my 87 cobra?

The impeller seemed to be in good shape, nice and soft not tore up, shaft was turning with impeller off. I am going to town tomorrow and will be picking up a service manual so I can determine the water flow route and break the system down piece by piece to try and locate the problem. That's probably going to be the best way for me to tackle it.

Re: Confused about cooling on my 87 cobra?

Water should flow out the prop as soon as the manifolds are full, the water will be somewhat cool 'till the thermostat opens. My first guess would be improper muff placement or not enough water flow, second would be clogged up manifolds.