Random Overheating

[venetrex]

My boat was overheating at idle. My raw water pump had some shaft play and a small leak. I replaced the entire assembly. Still overheated. Backflushed hoses and found weeds and hair in transmission cooler. Worked okay for a little while, few days overheated again. Check thermostat and replaced. Was ok but then overheateed yesterday. I am noticing my heat is not working when this occurs. Is it possible the water circ pump is bad??? I am getting a new one today, hopefully. The odd thing is it worked fine all day yesterday and then later on overheated. It comes and goes. VERY FRUSTRATING.

[TeamAllen]

What year boat is it?
What engine is in it?

[svtcobra50]

How long since you replaced your sea water impeller? Those things break off, crumble and stop up everything!

[venetrex]

my boat is a 2002 21v with a 350 mag mpi ski towsports. The raw water pump and impeller are new. I also changed the circ pump, looked okay though. However I noticed that the water distribution house has a leak. I am replacing that. I was told if that leaks the entire block will drain out through that thing when I turn the engine off. This could be my problem. it seems to happen after I shut it off and idle around to set up a skiier.
Will keep posted.

[svtcobra50]

OK. Please do.

[dogbert]

my boat is a 2002 21v with a 350 mag mpi ski towsports. The raw water pump and impeller are new. I also changed the circ pump, looked okay though. However I noticed that the water distribution house has a leak. I am replacing that. I was told if that leaks the entire block will drain out through that thing when I turn the engine off. This could be my problem. it seems to happen after I shut it off and idle around to set up a skiier.
Will keep posted.

BTW, those blue nylon nuts that drain the block, manifolds, water pump and fuel cooler have a tendency to get brittle and break off. I had that happen to me. Not only did I end up with a bunch of water in the bilge, I overheated as well.

[R&T Babich]

BTW, those blue nylon nuts that drain the block, manifolds, water pump and fuel cooler have a tendency to get brittle and break off. ...

I think they also have an O-ring on them.
Our boat was missing one and had a slow water leak.

[SPBFAN]

Any type of leak or blockage in the sytem will cause it to over heat. These systems are not as forgiving as cars.

[venetrex]

Mystery solved

I should kick myself in the head for this one. I changed the water distribution housing that had a crack. No leak, put thermostat back in and after driving and shut off it happened again. What I failed to take into account, but I swore this didn't happen last year is my ballasy sytem taps the seawater input for the boat, before the raw water pump. Apparently somehow it was introducing air into the system. I have 3 ballast puppies and a lot of piping. I closed my ball valve to the system and the problem has stopped now for 2 days. I will post this in ballast section two or if somebosy can for me. Moral of the story, DO NOT TAP SEAWATER PICKUP FOR ENGINE for ballast system. At least I changed a lot of minor troubles that I had. Ordered a new raw water strainer 1 1/2 for the system. Which should cure my trouble.

[dogbert]

I should kick myself in the head for this one. I changed the water distribution housing that had a crack. No leak, put thermostat back in and after driving and shut off it happened again. What I failed to take into account, but I swore this didn't happen last year is my ballasy sytem taps the seawater input for the boat, before the raw water pump. Apparently somehow it was introducing air into the system. I have 3 ballast puppies and a lot of piping. I closed my ball valve to the system and the problem has stopped now for 2 days. I will post this in ballast section two or if somebosy can for me. Moral of the story, DO NOT TAP SEAWATER PICKUP FOR ENGINE for ballast system. At least I changed a lot of minor troubles that I had. Ordered a new raw water strainer 1 1/2 for the system. Which should cure my trouble.

I had a similar issue when I tapped into mine, so I went with thru-hulls.