8.1L heat exchanger

Nmor830

Member
Sep 12, 2016
90
Channel Islands
Boat Info
2008 340 Sundancer
Engines
8.1l Mercruisers
Need to replace the heat exchanger on the strb. engine. It leaks around the end cap that pressed into the tube chamber. It’s not the rubber gasket or O ring. Thought of taking it to a radiator shop but not sure they can do the repair.
On line found an aftermarket one (mr. cool) for half the price of oem. Has anyone used one of these and if so with success? Thought I’d try for some feedback before placing order.
Thanks,
Nick
 
I just replaced mine with Mr. Cool............... It was actually pretty easy, and they shipped out same day. great customer service
 
If the end cap is warped it can be replaced, if the end of the HE has an irregular surface, it can be machined flat. Machine shop not radiator shop

If that's the only issue, the leak, this will be a lot cheaper fix.
 
just putting this out there-- I have two -vintage-2000 mercruiser oem heat exchangers from 7.4 mpi horizon h. o. motors. they are the 1/2 fresh water cooling system. FOR SALE very cheap. They were taken off at 1.5 years old when motor was converted to full fresh cooling. LOOK LIKE NEW> PM me.
 
8.1's have specific heat exchangers. They are not like the normal ones that have hoses attached so one from another engine is unlikely to be useable without some major modification.

Is yours leaking coolant or sea water?
 
8.1's have specific heat exchangers. They are not like the normal ones that have hoses attached so one from another engine is unlikely to be useable without some major modification.

Is yours leaking coolant or sea water?
I’m not sure? What’s bad it’s leaking directly on to the alternator. There’s green corrosion around the end cap which makes me think it may be sea water.
 
Need to replace the heat exchanger on the strb. engine. It leaks around the end cap that pressed into the tube chamber. It’s not the rubber gasket or O ring. Thought of taking it to a radiator shop but not sure they can do the repair.
On line found an aftermarket one (mr. cool) for half the price of oem. Has anyone used one of these and if so with success? Thought I’d try for some feedback before placing order.
Thanks,
Nick
I have replaced all coolers and heat exchanges to Mr. Cool on my 8.1S's. Salt water and Zero issues and half the cost. Three years ago.
 
I needed to replace my port engine heat exchanger this year. Went with Mr. Cool. Great service and good price. Good quality product. No made in China sticker to be found! I believe there are two different sizes for the 8.1. So check your engine serial number. If just a end cap leak, that may be a easy fix. If a internal leak, ‘tubes”. I would not mess with a repair unless it was a emergency.
 
I’m not sure? What’s bad it’s leaking directly on to the alternator. There’s green corrosion around the end cap which makes me think it may be sea water.

The end cap is easy to remove and much cheaper to replace if corroded. You'd see the coolant level dropping if it were leaking coolant (internally or externally). Mine was leaking coolant out of more than a couple of cracks in the brass tubes within the exchanger and getting flushed out the exhaust. At the time, the best replacement price was around $850 but that was 10yrs ago. Not too many aftermarket parts available at that time, but replacement solved the coolant loss issue.

https://www.marineengine.com/parts/.../0m026000-thru-0m319190/closed-cooling-system

See items 32,33 and 34.
 
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The end cap is easy to remove and much cheaper to replace if corroded. You'd see the coolant level dropping if it were leaking coolant (internally or externally). Mine was leaking coolant out of more than a couple of cracks in the brass tubes within the exchanger and getting flushed out the exhaust. At the time, the best replacement price was around $850 but that was 10yrs ago. Not too many aftermarket parts available at that time, but replacement solved the coolant loss issue.

https://www.marineengine.com/parts/.../0m026000-thru-0m319190/closed-cooling-system

See items 32,33 and 34.
The caps hold back raw water.
 
Need to replace the heat exchanger on the strb. engine. It leaks around the end cap that pressed into the tube chamber. It’s not the rubber gasket or O ring. Thought of taking it to a radiator shop but not sure they can do the repair.
On line found an aftermarket one (mr. cool) for half the price of oem. Has anyone used one of these and if so with success? Thought I’d try for some feedback before placing order.
Thanks,
Nick
 
Mine was leaking at end cap too mercruiser part diagram shows bolt then metal cover rubber gasket then o ring but repair book states make sure you put o ring between metal plate and rubber gasket.mine would leak at bolt when first did per diagram going out Sunday hope it stopped.
 

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