My Mercruiser 5.7 MPI is still overheating...GRRR !!!!

[newbienewb]

snatchy - thats a great post. Thanks for that. It makes sense as to why the check valve is there. The boat used to operated in queensland, so it may have been more of an issue up there.

I think ill run without it just for a period of time to see if it makes any difference.

On the up side.......i think i may have (read MAY) found a smoking gun. Going from advice in these threads, i started looking at the pickup from the leg, up through the transom and into the pump. Whilst i couldnt really be bothered pulling the leg off this afternoon, plus i dont have the required tools, i opted to limber up and dive in behind the engine to see if i could pull out the hose connector for the raw water on the inside. This would give me a direct look at the end of the hose where it meets the transom. I had a heck of a time getting the part off, but finally i manged. And in there i saw a significant blockage. It doesnt appear to be corrosion in full, but in actual fact a collapsed water tube insert???.............one of these.



Here is a picture of what i found. I contorsionised myself for these photos.





So - what do we think guys?..........confident?.

Whats the easiest way to go about fixing it?

Dave

[shaungonemad]

That can't be doing you any favours there can't be to many demons left in the system

[sharkymark2]

geez I hope that is it. You must have lost a fair bit of hair by now.

[StevenM]

Mate your onto it. That would be reducing water flow by more than half.

[The Woo]

Now ya talkin! Get better mate, then fix and enjoy.

[captain rednut]

Thats the water inlet fitting i was trying to explain, you done well and can now go boating with a cold engine.
Regards Jim

[captain rednut]

That is a very common problem and one solution is to block that failed fitting off and put a hull skin fitting in to feed the engine which is common but you will have to fit a sea strainer.
If you do this you will need to cut the inlet water hose off the transom shield on the outside to allow the leg to be cooled.
If you require any more info feel free to call me.
Jim 0418748023

[Moejoes]

Hi Dave,
I had a similar problem on a 32ft Searay with Volvo legs I bought.
It ended up being a corroded alloy fitting (similar to a Holden 186 thermostat housing) that was connected to the pick up hose half way up the leg that then ran up through the transom. Same thing, ran at normal temp then over heated straight away as soon as it planned because it was then sucking air.
The previous owners spent a motsa trying to fix it but couldn't diagnose the problem.
It cost me $40 for a new part & problem was solved.
Rob.

[snatchy]

That is a very common problem and one solution is to block that failed fitting off and put a hull skin fitting in to feed the engine which is common but you will have to fit a sea strainer.
If you do this you will need to cut the inlet water hose off the transom shield on the outside to allow the leg to be cooled.
If you require any more info feel free to call me.
Jim 0418748023

Hi Jim
If you do this as you suggest, does the leg still need its own impeller to keep it cooled? So the engine has its own through hull pickup and water pump, plus the leg needs its own to keep it cool? I have this setup already and was hoping to ditch the leg impeller so i only need one water hose to flush after use (Not the two hoses I currently need) but I am not sure of the cooling needs for the leg and I am starting to research this idea.
Apologies for the slight deviation off topic

[captain rednut]

Providing you have an engine sea water pump which im assuming you do?? yes we remove the leg pump totally and you can either cut the hose in behind the shield to allow cooling at speeds or fit a drive shower for $250 off Ebay.