Mercruiser Overheating

[macca110]

Hey There All,

Engine serial OFO63387,Bravo Serial OD869785.
Purchased boat after full survey was carried out including a sea trial.All good. Boat at home now on it's trailer. Starts right up and runs well with no noises.Engine is closed water cooled with heat exchanger.The second time I ran her up on muffs only, I let it go for a while, and after ten minutes or so she was up around 200,so I shut her down.I noticed the seacock thru the hull was off/closed,but there is a tap/valve between the seacock and the raw water pump with an open ended hose.When the boat arrived the hose with the tap had its open end sitting in a large bucket.
Hindsight is glorious...Should I have perhaps filled the bucket? And if so, would the seawater pump on the engine have sucked this up and ran normally?I'm going to replace the impeller and o rings as a precaution.

Please shed some advice and point me in the right direction.
The boat never got over 140 during the sea trial.No heat alarm went off when warm, so I'm hoping all will be well.
Thanks in advance,
Andy

 

[achris]

Re: Mercruiser Overheating

If you ran the engine without an external water source for 10 minutes then pull the raw water pump and rebuild it (with new everything!), the impeller will be way passed history....

Even though it has closed cooling, that coolant has to be cooled by something... That something is the seawater, or if you're running on land, an external water source, like a tap....

You have also likely burnt all the exhaust rubbers from the exhaust elbows south.... Check them out before they fill the boat with water....

 

[macca110]

Re: Mercruiser Overheating

Thanks,achris,
Will pull water pump tomorrow.Im installing a pair of brand new one piece stainless manifold/risers before the boat gets wet.So I will check all the rubbers then.I guess I'll need to pull the leg then? Assuming the water ingress would be from the rubber/s at the bottom end of the Y pipe? Thanks again.

Learning as I go,
Andy

 

[Speakrdude]

Re: Mercruiser Overheating

After 2 or 3 minutes there should have been massive amounts of smoke coming from the exhaust couplers!

 

[macca110]

Re: Mercruiser Overheating

If You mean the rubber between the risers and Y pipe,not that I could see.I had the engine hatch up.There was a bit of smoke from the exhaust rubber at the transom though.Then I shut it down.
Yes,Hindsight is 20/20.
I just hope the engine will be ok.
The oil looks clean and has no burnt odour.
It starts and runs as smoothly as it always has.
The temperature guage works well.
It may be irrelivant but the closed water coolant is clean and the catch can shows no coolant loss.no engine alarm went off and they're operational.
So,I guess I have to pull the leg to replace the Y pipe rubber then?
Thanks,Andy

 

[macca110]

Re: Mercruiser Overheating

Hey there All,
as predicted the impeller and plastic housing were damaged but miraculously,came out broken but intact.Al bits were present and accounted for.
Although the metal part of the pump appears fine,are they servicable?
Are the bearings able to be replaced?
If so,How do I take it apart?
Thanks, Andy

 

[achris]

Re: Mercruiser Overheating

What parts you chasing?

 

[macca110]

Re: Mercruiser Overheating

Wow! Thanks achris.Tell me how dismantle check/replace the internals re parts 15 thru 19?
Everything else is new on pump, and pulleys ,tensioner and belts just done.
Andy

 

[achris]

Re: Mercruiser Overheating

Send me a PM with your email address. I have extracted the cooling system section from the service manual, but it's too big to post up here.... Make sure you have Adobe Reader X...

Chris.......

 

[macca110]

Re: Mercruiser Overheating

Hey there All,
I have pulled the internals from the metal part of the pump to inspect for damage.Surprisingly there was very little.However the problem I'm facing now is finding a rebuild kit to rebuild it.
Do they even exist?
Is there anyone who can help?
The bearings came out,but I sacrificed the pulley,circlip and all seals to get to the bearings.There must be somone who sells these parts.
Otherwise why give an exploded view with details and part numbers for each bearing and seal?

 

[achris]

Re: Mercruiser Overheating

Otherwise why give an exploded view with details and part numbers for each bearing and seal?

Here's the list of part numbers to go with the exploded view I gave you....

Chris......

 

[macca110]

Re: Mercruiser Overheating

Thanks Mate.Managed to track the parts down and have purchased.Won't run it this way again thats for sure.