Advice re overheating issues

[tgebler]

I have a 2000 396 aft cabin with twin 454 Mercruiser gas engines. I started having an issue with slight over heating in the starboard engine and steam coming from that side while running. My mechanic found and replaced a bad impeller but that did not fix the problem.

He told us the next step was to tear down the engine for a possible blown heat gasket or other problem. Of course, the dollar signs began to appear. In light of the season hear in Pittsburgh, we decided to haul the boat to perform the work.

I received a call from the mechanic today advising he found debris at the inlet which was blocking the flow of water but had not made it to the strainer. He thinks the debris was the cause of the problems.

We also had a leak of the starboard shaft seal which is water cooled but the mechanic believes the shaft seal failure was caused by the overheated water.

A strange turn of events but now just need to replace the shaft seal and hope for the best. I thought the group might find this tale of woe interesting.

[Miss Fire 2.0]

yes quite often when an impeller fails, all the blades or parts there of end up in the cooling passages. primarily the thermostat housing and head passages. its a good idea to change impellers at least every 3 years.. sounds like you may have dodged a bullet. Good luck, been there..

[Miss Fire 2.0]

woops, It was debris blocking the intake which caused the impeller frailer, sorry disregard previous.

[Cooler]

That debris was likely creating a cavitation effect. Those lines need to be clear. I would also replace the t-stats to be safe. low cost project. Good luck! er

[Viper]

Source of the post I have a 2000 396 aft cabin with twin 454 Mercruiser gas engines. I started having an issue with slight over heating in the starboard engine and steam coming from that side while running. My mechanic found and replaced a bad impeller but that did not fix the problem.

He told us the next step was to tear down the engine for a possible blown heat gasket or other problem. Of course, the dollar signs began to appear. In light of the season hear in Pittsburgh, we decided to haul the boat to perform the work.

I received a call from the mechanic today advising he found debris at the inlet which was blocking the flow of water but had not made it to the strainer. He thinks the debris was the cause of the problems.

We also had a leak of the starboard shaft seal which is water cooled but the mechanic believes the shaft seal failure was caused by the overheated water.

A strange turn of events but now just need to replace the shaft seal and hope for the best. I thought the group might find this tale of woe interesting.

I have a couple of problems with what they're telling you. Telling a customer he needs an engine tear down before exploring all other possibilities through proper diagnosis is a real problem. Imagine if they didn't catch the debris in the intake, you'd have the engine work done ($$$$) and you'd still have the same problem! They'd still make you pay for the unnecessary work though.

You stated that it was a "slight" over heat. If there is any water flow, it should be going through you manifolds which is typically where the lubricating water for the shaft logs comes from. If it was a slight overheat, I doubt it had any effect on the seals. Also, if the raw water plumbing to the seals is a typical install, they will have two lines going to each seal so that if one engine fails or is overheating, water from the other engine will still lubricate both logs. Yours may or may not be set up this way but that's usually the way they are. If the seal is leaking, it's more likely due to old age, debris, or starvation of water to cool it.

Are they Tides lip seal dripless logs? Is there a spare seal kit mounted on the shaft before the shaft log?