Boat overheating fast

[sebas54]

Hi I have gmc 4.3l merc alpha 1 today I went out and didn't get to far. The engine overheated in 45 seconds. I checked the thermostat and it was operational, also checked the inlet line from the raw salt water and water was coming out but not very fast, especially when at idle (barely nothing coming out at idle). How much water is supposed to coming out of the house coming from the impeller. I have changed the impeller just under 2 years ago. Today before I went out I ran the engine without out any water supply for tops 15 sec. at a time, about 3 or 4 time. Could that have caused the impeller to get damage?

I am thinking the impeller need to be changed but I am not certain. I was also thinking the circulation pump might be bad but not sure. Any advice is greatly appreciated.

Thanks

 

[Don S]

Re: Boat overheating fast

Today before I went out I ran the engine without out any water supply for tops 15 sec. at a time, about 3 or 4 time. Could that have caused the impeller to get damage?

Absolutely that could be the problem. The impellers should never be run dry. When you pull it apart, make sure you check the housing and base, being plastic they may have melted and/or warped.

 

[Bondo]

Re: Boat overheating fast

Ayuh,... Sounds like ya ruined the impeller, 'n possibly the pump housings...

Get a rebuild Kit, 'n do it up...

 

[old377guy]

Re: Boat overheating fast

yep, like Don says. good luck.

 

[mohavafish]

Re: Boat overheating fast

don't mean to intrude but be sure to check the seal below the water line housing (see picture) I have talked to quite a few people that missed it and are still overheating on plane.

 

[Bondo]

Re: Boat overheating fast

don't mean to intrude but be sure to check the seal below the water line housing (see picture) I have talked to quite a few people that missed it and are still overheating on plane.

View attachment 87384View attachment 87385

Ayuh,... Yer Volvo is Nothing like his Mercruiser...

 

[mohavafish]

Re: Boat overheating fast

I realize that and I was not implying it was. I was simply stating an idea that perhaps looking at all areas that are involved with the intake of water to the engine are suspect. next time I promise not to intrude and keep my 2 cents to myself. sorry about that.

 

[HT32BSX115]

Re: Boat overheating fast

next time I promise not to intrude and keep my 2 cents to myself. sorry about that.

Now now, don't feel like you were "intruding"! Sometimes the "intruder" has the right answer!

Along those same lines, for the original poster, you might also want to check the (raw water supply) hoses from the drive to the T-stat housing, and maybe pull the t-stat housing to have a look inside.

You'll be looking for pieces of previous impeller failures that allowed those pieces to get past the pump housing, into the power steering and engine oil cooler (if installed)........(you probably don't have an engine oil cooler) those pieces might even be lodged somewhere in the hose from the drive.........

I had a similar problem with my Bravo. The previous owner assured me that he changed the raw water impeller. He did(although it didn't look all that good.) The one (or more) before that though, was literally CRAMMED into the oil cooler. (the pieces made it past the PS cooler though I guess because they were small enough)

I don't know how ANY water got past the oil cooler though as thoroughly plugged as it was!......the PO insisted that the engine didn't over heat.......

I have found that I don't generally believe what "Previous Owners" say about most everything!!!