Water getting into the motor!

[Shrimp Claw]

My father in law bought a used inboard jet a few months ago. It didn't have a trolling motor, but had a plate where one goes and the old owner had one on it before so we bought one and put it on. We used the boat 6 or 7 times in the bay with no problems. Whe last time we took the boat out it would not start, it turned over fine and tried to start a couple of times but just wouldn't. Took the boat in this week and the mechanic sait the engine was froze up with rust. He said water got into the motor through the exhaust ports. He said that if the kicker motor creates a lot of turbulence, which it does, it forces water up into the exhaust ports and then into the exhaust manifold which caused the motor to rust and freez up. I'm no mechanic, but how can water go up these ports and rust the engine. We have the boat set up like it should be. How else could this have happened or what can we do to prevent it. It ended up costing about $3000 to get it fixed.

[gon troln]

Shrimp Claw, I'm not sure what type of boat you have, how ever on my sled there are rubber flaps on the exhaust that prevent the back streaming of water. I'd check to see if thats the case. In some inboards there are flaps in the riser to prevent this also. Good luck and let us know what you find.
gon troln

[fishkisser]

It wouldn't be a sportjet , would it ...

[DK]

What motor are you running?

[Okie]

There is something else going on with your engine. You said you used it 6 or 7 times with no problem. It seems if the problem was caused ,as you think ,it would have happened a long time before you ever bought the engine.

[bandwcow]

Some engines will diesel after they are shut off. Maybe you have seen this in a car or truck engine. If a inboard motor like you are describing diesels after being shut off, it will suck water up through the exhaust ports into the cylinders and can even occur if you have flaps over the exhaust ports. That is if they are underwater.

Sounds like your engine dieseled after you shut if off, not realizing it sucked water into the engine. Something I have heard of more than once. After running your inboard hard always cool the engine off like walking a race horse after a good run.

[Baxter]

Originally Posted by Shrimp Claw

My father in law bought a used inboard jet a few months ago. It didn't have a trolling motor, but had a plate where one goes and the old owner had one on it before so we bought one and put it on. We used the boat 6 or 7 times in the bay with no problems. Whe last time we took the boat out it would not start, it turned over fine and tried to start a couple of times but just wouldn't. Took the boat in this week and the mechanic sait the engine was froze up with rust. He said water got into the motor through the exhaust ports. He said that if the kicker motor creates a lot of turbulence, which it does, it forces water up into the exhaust ports and then into the exhaust manifold which caused the motor to rust and freez up. I'm no mechanic, but how can water go up these ports and rust the engine. We have the boat set up like it should be. How else could this have happened or what can we do to prevent it. It ended up costing about $3000 to get it fixed.

I don't think a kicker, or dieseling, or even a surge against the exhaust port should cause water to back up into the motor. These things can only happen if your exhaust system is poorly designed. Your exhaust should run through risers that are sufficiently high above waterline to prevent water backing up into the engine. Before running your boat again, after a $3000 repair, check the elevation of your exhaust risers or elbows against the waterline with the boat at rest. I don't know what the recommended rise would be for your configuration, but if you don't know either, you need to ask around until you get an answer. You may very well need to get some custom risers built.

But, if your mechanic didn't do anything to prevent this from happening again, I would think several things: First, he may have misdiagnosed, and water intrusion from the exhaust port wasn't even the cause of the starting issues. Second, he may have missed a leak, like in a rotted out or poorly oriented mixing elbow, that could be the true cause of the water intrusion. Third, it's time to get proactive and figure out for yourself how your motor really works and what went wrong. Just writing checks doesn't really fix these things, unfortunately.

G'luck, Lee

[Okie]

Doing mechanic work myself, I have often found errors made by other mechanics. And this case seems to fall in that area. "Baxter" comments, are right on this.

Making your own inspection and finding the trouble your self is the best way to save yourself a lot of money.

Good Luck