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Mercruiser overheating

"The middle runner on a v8 int

"The middle runner on a v8 intake is between 2 exhaust ports and is typically hot! That is where the choke bymetal spring is located on the older mechanical choke systems.
Wrong location to be looking at temps.


look at the location that the sending unit is located.

If you have a lot of air in the incomming water supply you have to remove the lower unit from the outdrive to look at the water pump impeller and housing condition.

If you do, Take some pictures and post."
 
"I'm new to the forum as o

"I'm new to the forum as of today and I am not sure that I should post my problem here. If not, I would appreciate some direction of where I should go.

I have a 2002 Sear Ray 280 with 4.3's. I have a heating issue with my Starboard engine. It overheated a few weeks ago (right after I bought it) and I took it to a Marina for repair. Result - new engine - but the old problem is still there. At low RPM (up to 2500) everything is fine - try to go to plane and the engine heats to 220 before I can get it up. Go back to low RPM and the temp drops to normal immediately. They installed a new thermostat and that worked for one day. Next time out the same old problem. Even with the new t'stat the temp was 170 (gage is off by 7 degrees)on the day it ran. Power seems to be down as well.

Any suggestions?"
 
"Jerry;
Welcome to the forum.

"Jerry;
Welcome to the forum. Nice boat!
You should likely start a new topic; but your problem could easily be the same; ie pump is sucking air and not enough water.

You should try the transparent hose idea per the above disucssions, and see if there are any air bubbles in the water stream. If there are, your drive leg pump needs serviceing.

Rod"
 
Should i use gasket sealant on

Should i use gasket sealant on all gaskets on the water pump cause i only used it on the pump base?I will remove lower unit and get some pics up.
Thanks Josh
 
"Josh;
I have never used any

"Josh;
I have never used any sealant, but then I have never had the air leak problem either.
There may be other sealants you could use, but marine RTV should work well.
Make sure the parts are clean and degreased well.

Hopefully others will chime in here with other sealant suggestions. There was a similar discussion on this board within the last 2-3 months as I recall.

Rod"
 
Spray tack in a can works pret

Spray tack in a can works pretty well. It allows you to coat one or both sides w/as much as you think you need; but a thin layer works great. PIA when disassembling; have to clean all of it off w/solvent and gasket scraper.

I saw one old fleet mechanic use it on battery terminals. I asked him why; he said because it covers so well.
 
"<[img]"http://www.marineengin

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1st pic = Pump in lower unit

1st pic = Pump in lower unit

2nd pic= Looks like exahust gas and water have got on this shaft!! Not good is it

3rd pic= Gasket and ware plate looks good!

4th and 5th pic= Base plate looks like it got a little warm !! Why its brand new

5th pic= Everything out it all looks good.

Thanks for the help
Josh
 
"I have a 1980 Mercruiser 470

"I have a 1980 Mercruiser 470 that overheats at higher RPM's. Ive checked the OD Impeller, Thermostat, Hoses and Water Pump and all seems fine. Could my overheating be due to a blown head gasket?"
 
Ken:

Please start a separat

Ken:

Please start a separate thread for the most responses. First thing I would suspect is the heat exchanger needs cleaning.
 
"Josh:

Shoot me in derriere

"Josh:

Shoot me in derriere; I scrolled down and not across! Duuuuuuuuuuhhhhhhhhh.
crazy.gif
"
 
Josh:

Did the shaft cleanup

Josh:

Did the shaft cleanup? Pics. 4 & 5; it doesn't take much to cook one. How is it coming?
 
Guy
Shaft cleaned up good.Sh

Guy
Shaft cleaned up good.Should i get a new base or can i clean this one up? Do u think i had the top cover to tight and thats what caused the base to melt? Maybe it was not letting the impeller move freely and it was diging into the base plate?
Thanks for all your help i know im a pain in the a$$ Josh
 
Replace the base and install i

Replace the base and install it and tighten the bolts and screws per the service manual's instructions. Make sure the bottom oil seal pops into place. A thin coating of 2-4-C lube on the shaft won't hurt anything.
 
"When doing a water pump servi

"When doing a water pump service as you are doing you should always replace both the water pump housing and the base assembly.

As said grease the seal lips a bit with grease and make sure you put the correct o-rings and gaskets back in place. Look at the old one carefully so you know which new ones to use. The kits come with several that are for slightly different pump housings.
Do not forget the large fat o-ring that sits on top of the water pump housing,

As far as the melting goes yes you could have overtightend the nuts but it is more than likely due to heat and lack of water.

Bet you or someone fired it up without the muffs or the water running, or the outdrive out of the water????? inquiring minds would like to know."
 
Also from the pictures you see

Also from the pictures you seem to be missing a washer that sits on top of the shift shaft seal???
 
Kghost
Yeah my dump butt had

Kghost
Yeah my dump butt had a brain fart one day and i killed the water to the muffs befor i killed the engine.Didnt think i did any harm.But it looks like i did.Also the shift shaft seal you are talking about is this like an o ring or a flat washer there was nothing there when i took it apart?.Thanks for your help
Josh
 
I have one question now that i

I have one question now that i have the lower unit off can i run a hose to the copper tube in the upper gearhousing and run the motor to find out if my over heating problem is with the water pump or the engine.With no oil in the upper gearhousing??? Thanks Josh
 
"Do not run upper alone. 60 se

"Do not run upper alone. 60 seconds without any gear lube and the bearing in the cap will be toast!!

If you are having an overheating problem you need to use the outdrive impeller to supply water for a better evaluation.

Here is your picture with the shift shaft seal circled.

The bronze shift arm is not supose to sit directley on this seal.



217994.jpg
SHift Shaft Seal location where washer goes
 
"I had the same issue (air

"I had the same issue (air dilivered to the engine) not yet resolved. May I suggest that you take a psi reading in all the cylinders, I am hoping that the over heat did not do any damage to the gaskets on the engine. If you have good psi in all cylinders then I would suggest that you remove the othe manifold and replace it.I understand that they are expensive, how ever they are less expensive than an engine replacement. From prior threads and responces from Guy, I learned that you can have an over heat issue when the head gaskets are malfunctioning. Just a suggestion"
 
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