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Merc 470 heat exchanger seals

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perch_chaser

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"Tonight was test fire night.

"Tonight was test fire night. Backed into the launch, and fired up. My trusty old 470 was right on as always, but I have water flowing out of the back end cap seal on the heat exchanger. What is the best sealant to re-seal the end caps? I was thinking blue gasket sealer, but not sure. Thought I would ask, so I only have to do this once.

Thanks in advance....."
 
"might try hammering them flat

"might try hammering them flat first, common mistake is overtightening or failure to winterize the raw water side,this causes the plate to bulge."
 
"Good point, I did notice they

"Good point, I did notice they were dished when I pulled them off. I have winterized her they same way all 4 years I have had her, and never an issue. Wondering what I might have missed to cause this. It is the first time I have had to do any repair to the heat exchanger.

Thanks"
 
"Absolutely!

That is what I

"Absolutely!

That is what I found rather odd, there is no signs of swelling, and the pit-cock is right under the back end cap. I leave it open when I winterize and prop the front of the exchanger up so any "puddle" of water can drain out. I am certain there was no water in it. I held the exchanger over a light last night, insides look good."
 
unless i`m mistaken the heat e

unless i`m mistaken the heat exchanger has a upper and lower component to flow the water.it just dosent come in one end and go out the other.
 
you are correct BT it is a dua

you are correct BT it is a dual core.so one has to make sure they drain both passages. those things are so fragile because of such little hives sorta speak where the water lays.
 
"I have always bee pretty care

"I have always bee pretty careful about making sure there is no water in it, as at the price they want for one of these, it is not something I want to replace because of my own carelessness! If I did not have all the water out, wouldn't I see sings of expansion, or splits when looking through the honeycomb? it all looks good. this is the first time messing with the exchanger on this boat, other than winterizing. The only oddity I found was the end caps were dished when I took them off. Isn't that a sign of over tightening the bolt?
It is possible I missed something during winterizing it, but I a very care to follow my procedures.
That also raises the question in my head- should I be looking for something else damaged, if so what?
Thanks for all the input!"
 
"overtightened or expanded fro

"overtightened or expanded from water that started to freeze.Should you wish to leave it dry, blow air from the inlet hose to the outlet hose,or use the air hose and then fill the heat ex with A/F on the raw water side."
 
i always take the front cap of

i always take the front cap off and just lossen the back cap and tilt the boat down all the way in the front and let sit for a day then i raise the boat as far up as i can and pour antifreeze in the exchanger and let it sit for a day then drain it i also pour r/v antifreeze backwards thru the bilge pump with a flexible funnel but i do find it bizzar that both plates dished. some found it crazy i know when i posted that i put a half gallon of antifreeze in the hull and swished it around i figured this could only help control the hidden water in there and also the rodents that thought it tasted good
 
"Good, I am not the only one w

"Good, I am not the only one who pours antifreeze down the hull. I have a drain tube from the front floor storage to the bilge. I pour it down that drain too."
 
My Mercruiser was leakin there

My Mercruiser was leakin there as well and what i did was remove the end camp.. grinded it down... and flated out the cap.. and then i noticed that along the side near the back cap it was a thin crak line that it was leakin from .. so i sanded it out all around the end of the exchanger and cleaned out the crack and then soldered the end .. and it works like a hot dam.. so if there is a leak on the end somewhere.. try fixing it.. works good..
 
The HE end cap bolts require 7

The HE end cap bolts require 70lbs/INCH of torque. Not much. Also look at the thick rubber gasket for failure or splits or possibly your HE is cracked. Mercruiser suggests using new seals whenever they are removed and also using "Perfect Seal" on the end cap seals. I'm sure there are equivilents out there if you google it.
 
my front/bow one had a steady

my front/bow one had a steady drip not bad but aggravating i took the seal off and turned it around and walla fixed the drip but napa tells me they can order them seals
 
"It is fixed! I hammered the e

"It is fixed! I hammered the end caps flat again, and upon a close inspection, found nothing else wrong. I turned the rubber seals around and used soft set RTV gasket maker to seal them up. Ran it yesterday for a couple hours, and no leak

Thanks to all for the insight!"
 
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