Surprise! (Heat Exchangers)

[Ken Juul]

Last season the engine was running hotter than usual, it would creep toward 170-180 after extended motoring.   Pulled the heat exchanger off the boat in Nov, been sitting in a bucket of water to keep any deposits moist.  I finally got around to cleaning it last night.  Much to my suprise when I pulled the end cap off, the intake end was almost completely plugged with big pieces of impeller blades!  I've burned up a couple of impellers in the last 6 years but I always try to reconstruct the impellor by pulling pieces out of the pump and hose.  I'm confident that I've gotten 99% of the pieces, so what I found must have been from previous owners.  I am theorizing that most of the pieces were stuck in the hose and finally made it to the heat exchanger last summer.

Ran a straightend out coat hanger down the tubes to loosen things up and soaked the heat exchanger in 20% muriatic acid (Ace Hardware $5/gal) until it stopped bubbling (3-4 minutes) rinsed well with water.  It is clean as a whistle End caps go on tonight, then new paint.  I have a roll of sheet rubber from a previous project so I made my own end cap gaskets, according to Ron Hill new gaskets are available at Glenn Mar Marine (800)282-0123 for the SemDure @ $1.50 gasket (#0332). 


To owners of previously owned boats.  If you have any overheating tendencies, make sure you pull the end cap off and take a look.  Check/replace the hose between the raw water pump and HX for stray impeller blades.  Hopefully you won't be as surprised as I was.

[sdaly66]

Ken,

Thank you.  A very timely message for me.  I'm having the survey done next week on what I hope will soon be my C 34.  I'll make a point of having the surveyor check this.

[David Sanner]

Years of zinc buildup will also restrict water flow.

I cleaned my extra zinc out by removing both of the
end caps on the heat exchanger and blasting the
zinc out with a hose from the opposite ends. 

With a Globe Run-Dry impeller my temp gauge never
moves the opening temperature of my thermostat.
(50-60 degree SF Bay water makes sure of that)

[DougP]

Took mine to a local radiator shop. They cleaned it, pressure tested, re "rounded" the hose fittings, made new gaskets and primered it for about $60.

The would have painted it too, but only in black. I of course opted to order expensive bronze colored Westerbeke paint and finish the painting myself. Looked real good until I was putting on the last coat and it fell from the hook and landed, wet paint and all, in the sawdust and metal shavings on the floor.

[Ron Hill]

Ken : I'm NOT surprised.
I'm glad that you posted your message along with David's impeller suggestion.
It all goes to backup my many messages/posts saying that all this information has already been written in the Mainsheet tech notes!
 
Guess it takes MANY MANY reminders of: find all the broken impeller blades or use a Globe impeller that is less apt to loose a blade!
 
Good info in those OLD Mainsheet Tech notes - read them, they still provide valid guidance!!   

[Stu Jackson]

While we're discussing heat exchangers: I spent the weekend taking out the HX because, silly me, I didn't listen to my own instructions and replace the zinc last September!  It was stuck inside and the only way to get it out was to remove the whole thing.  Oh well, another lesson learned.

I upgraded to a new 3 inch HX three years and 567 engine hours ago on our M25.  It's been running everything fine and cool.  My engine maintenance log has a special space at the bottom for "new HX zinc" replacement, every three or four months.  I checked it in August and it looked fine, so I wrote down Sept 2006.  Then I got stupid, and lazy, hence the story above.

While it's out, check the smaller raw water intake tube - it builds up with salt deposits and can restrict the flow.  That's the intake tube on the HX itself.

[Tom Soko]

Doug P,
If you don't want to pay the Westerbeke prices for the traditional bronze colored Universal paint, you might check with your local auto paint supplier.  For just a couple of bucks, I was able to buy spray cans of GM #286 (Camel) paint.  The color is as close to an exact match as anything I have seen.   Hope this helps.

[Ron Hill]

Guys : SEE, even the C36 people read what's in the C34 Mainsheet tech notes - when Hank published the lower cost paint of similar color for the M25 series engines!!!   

[DougP]

Thanks for the paint advice. I also checked with Rustoleum about the temp range for their hammered finish paints. They said it would up to 200 with no problem. May try that next time. Puts a tough, textured finish on.

[Jeff Kaplan]

stu, i still have the original 2" hx on my m25. have had it cleaned before. when you switched out to the 3", was it a simple swap out, and where did you get it. also, does the new one really make a big difference?...jeff

[Jim Price]

Another point on the HX that I don't believe has been mentioned recently.  Last summer when my diesel mechanic was doing "health check" on the engine  (I do 90% of the work but have a real mechanic check things out periodically), he discovered my HX had a broken bracket. 

Problem could have been much worse.  He took off to either repair bracket or replace.  Had to replace with new HX,but that is OK after 15 years anyway.  The HX could not be repaired because the broken bracket was allowing the HX to rub on the transmission housing when underway.  The wall on the bottom had place that was worn thin to the point of failure.  Then problem would have been really bad.  This was not an apparent problem because of the bracket position and the wear point located under the HX.

Just a note to look for other not so obvious failure points.   

[Stu Jackson]

Jeff,  It makes a difference in that I can run at full throttle for an extended (over 1 minute) period without overheating.  The temperature stays (+/-5F)at whatever the thermostat I happen to have installed is set for (160 or 180).  I bought it at our Universal dealer here and it cost about $250 $300 to plus parts four years ago.  "Big" difference, operationally no, peace of mind, yes.  I had posted many times about my exploits with our old 2 inch mariachi band HX  and how very efficient I was getting at removing, cleaning and replacing it.

Jim's point about abrasion is well taken.  When I had our HX out I noticed some rubbing, not against the transmission in our case, but against the support bracket.  Nothing major, but evidence after three years could lead to damage after 15. 

So what I did was to install a bicycle inner tube between the support bracket and the HX.  Just like the OLD Tech Notes suggest.

[Ken Juul]

Jeff,
It is kind of hard to see due to it's location, but fairly easy to remove, even though much of it is by feel.  I remove the Flame arrestor and lay an old work pad over the top of the engine and do everything from the top. Loosen the hose clamps and pull off the large hose to Coolant tank, large hose to engine water pump, small hose to raw water pump & small hose to exhaust.  Remove 2 mounting bolts located underneath on aft end of engine, 1/2" wrench if I remember correctly.  Swapping should be as easy as removing the old and reinstalling the new.  I think it will take longer to burp the cooling system than to do the actual swap.

[Ed Shankle]

Jeff,
Hansen Marine over in Marblehead has the heat exchanger. Think I paid @$300 a couple of years ago.

Ed

[Jeff Kaplan]

thanks guys for the info. might have to wait till next year, though, with  the new traveler, bimini and assorted other blocks and clutches coming. only so much money to pass around. ed, thanks for the reminder, know the place well, had to get parts there for atomic4 in my past c27....jeff