Exhaust couplings caught on fire!

[copelandcf]

Hello, I'm new to the forum and boating. I recently bought a 1988 Chris Craft Cavalier with the Mercruiser 3.0L 4cyl and Alpha One outdrive. The boat had been sitting for 8 years in a garage. We got it running on the water hose and took it on its first voyage last weekend. Everything seemed fine at first but after about 1 min of cruising I tried to open it up, which worked fine for a minute, but after I slowed down and tried to re-accelerate it did not have much power. To make a long story short, we noticed smoke, killed the engine, opened it up and the rubber couplings on the exhaust outlet had caught on fire! I dont know much about how boat engines work, but the fact there is rubber on the exhaust outlet makes me think water must get pumped into the exhaust manifold to cool it down. So I'm wondering if my impeller is shot, or if the water pump is, or if the rubber was just so old it caught on fire? Also it looks like the exhaust bellow started to melt, and there were pieces of burnt rubber inside the prop. I think the lack of power was due to the smoke in the bay suffocating the engine.

Any advice? I'm so new to boats and I'm having trouble finding the basics of how this or any boat engine works as far as cooling, intake, and exhaust. Any help is appreciated.

FYI, the only work I have done so far is clean carb, clean fuel tank out really good, change plugs, and clean ignition points. Thanks for any help.

 

[DJ]

Re: Exhaust couplings caught on fire!

Sitting for eight years and you did-NOTHING-to the cooling sysyem!

Not scolding, just sad.

You're right, the impleller is #1. Now you have other issues. Maybe expensive.

You may have toasted every rubber/plastic part in the whole cooling system.

You need to start from step #1. Renew every maintenance part. Start with the impeller and go all the way through to the riser and exhaust manifold.

Don't forget the Gimbal.

 

[TilliamWe]

Re: Exhaust couplings caught on fire!

1st get a factory manual.

Second get out your wallet, cause you have many parts to replace.

Most boats (meaning yours) use a water cooled exhaust manifold/riser/exhaust system. In fact, since there is no radiator, there is a constant flow of water to the engine and the exhaust, from that impeller pump in the drive. The fact that your exhaust hoeses caught on fire means that the impeller in your outdrive's lower unit quit pumping the water from body of water you were in and the entire engine/exhaust system went dry and got HOT from having NO cooling water.

 

[copelandcf]

Re: Exhaust couplings caught on fire!

Thanks for the replies! I'll replace the impeller asap, none of the other hoses seemed to burn up though. I've read to check the gimbal bearing while I have the engine open. Is there a water pump on this engine? Or just the impeller? It was getting water through on the hose, but I guess the pressure of the hose was forcing it in, and when it was sitting in the water on the lake the impeller couldnt get water in cause there was no pressure. Is this common?

Is the impeller relatively easy to do, and the gimbal bearing? Any how-to's on the internet, or just need to get a service manual? Do yall recommend I take it to a shop instead and if so how much does that cost?

Thanks again for all the help.

 

[Don S]

Re: Exhaust couplings caught on fire!

I've read to check the gimbal bearing while I have the engine open.

The gimbal bearing has nothing to do with the exhaust, and you don't have to open the engine to access it. You do have to pull the outdrive, and when you do, yes check the gimbal bearing. but you really need to check the engine alignment with an alignment bar.

Go to the link below, and you can download the OEM manuals for your engine and drive. You will need #10 for your engine, and #6 for your drive.
http://forums.iboats.com/showthread.php?t=251571