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Barber
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Broken down in Anacortes with cooling issue

I have been towed to Cap Sante with a cooling issue and I'm running out of ideas. Is there a local person that has expertise in this area? My boat is an 89 with the M-25XP. Local boatyards are at least a week out to send a mechanic. 

I will update this post with the symptoms and what I have tried. 

Thanks. 
Hector 

1989 Tall rig #964, Seattle

Barber
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We were cruising in the San Juan Islands for several days and everything was working fine with a healthy exhaust and temperature gauge down the middle, 170-180 degrees. Late one afternoon while anchoring the engine temperature gauge started climbing while also showing white steam from the exhaust.

First thing I tried was cleaning the intake raw water strainer which was kind of dirty so I thought that was that. Next day started motoring and after a few minutes engine started overheating again. We were in a bad spot due to conditions and to cut a long story short anchored in the closest protected shore and called for a tow. Eventually got to Cap Sante marina in Anacortes. Another long story for another day.

I should note the boat is new to me and I have little knowledge of pre-existing issues.

After getting to a dock I confirmed there was almost no water coming from the exhaust through-hull, just steam.

Things I have tried since then:

Raw water impeller. Looks in good shape and is intact and flexible although pump overall could be refreshed. Added some grease to center of impeller on cover side. I have an extra impeller but doesn't seem I can change it without a press. I have confirmed that water does come out of the pump however doesn't seem like it's a lot. Should the water volume increase with rpm?

Heat exchanger. I have the 3" Universal version. Took it apart and the section with the drain showed lots of zinc debris and blockage. Soaked it overnight in Coca-Cola. In the morning cleaned all the crud and ran lots of fresh water. There's now a good flow of water through every connection. Zinc is around 30% so needs to be replaced very soon as well as gaskets. No leaks.

Exhaust. Unplugged the hose that takes raw water to the exhaust manifold and put a hose there. Run water and confirmed it flows well to the exhaust through-hull.

Refilled the system with coolant and ran the engine for a while. Added coolant again. Repeated a couple of times until coolant level stayed consistent. 

There's is now water coming out of the exhaust when the engine runs, however it does look like less than normal. When water comes out, every 5-6 seconds, it gets sprayed out, does not stream. 

If I idle the engine at 1000 rpm and neutral the temp stays around 180F. However if the engine is under load the temperature starts climbing slowly but steadily and after you get to 190F steam starts to appear. Higher rpms will produce more frequent water discharge from the exhaust.

Any ideas appreciated! Mechanics are all at least a week out so I'd also love referrals to professionals that can help in the near future.Thank you!

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Catboat Willy
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Hector, 
Regrets that you are having this difficulity on vacation. What a bummer ! It sounds like you've done everything correctly in cleaning out the cooling system. Did you check the water heater and insure that is not clogged or blocking flow ? New thermostat ? Second thought. The actual sea water temperature is heating up and you might want to take that into consideration. Do you have a laser- hand held thermometer ? Is 190 the actual temperature or just what is indicated on the 30 year engine guage ? (you can tell I don't trust them) Has the temp been creeping up or did this happen suddenly ? Did you 'burp' or purge the air out of the cooling system ? Might be just an air lock in the cooling system.
Bill
 

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jerryr10
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I am having North Harbor diesel working on my engine for the same problem now in Cap Sante. They are changing the heat exchanger and the coolant water pump and thermostat and housing. I have the same engine that runs at 180 at 2300 RPM but if I go higher than that it wants to go to 190. I don't know how much of a back up they have But I trust Jim as a mechanic.

Barber
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My engine was happy crusing all day at 2600 rpm and 180F, both indicated so must account for margin of error. Does your engine settle at 190F? According to the manual the operating temperature is 165 to 195 so that would be within spec. 

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jerryr10
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Did you check the through hull with the strainer off to make sure you don't have some thing clogging the intake?

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pkeyser
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Another thing to check is the face plate on the raw water pump. Not 100% familiar with Sherwood, but on the Oberdorfer pump, over time, the impellor can wear the faceplate. It only takes a small amount of wear to reduce suction and raw water flow, especially at higher speeds. If the face plate has a wear sufficient enough to be felt with your fingernail, then grind it back to flat (with fine sandpaper on a flate surface), or reverse the face plate to the new side. 

Barber
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I have an Oberdorfer N202M-15 and on inspection looked fine although I will clean it up and replace all consumables in the near future. 

Barber
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After many troubles and tribulations the issue ended up being a blocked intake thru-hull. Strangely enough it was just restricted and after I changed the pump impeller the blockage was almost complete. Shooting fresh water through the seacock cleared it out. Probably eelgrass since the issue started in a rather grassy cove in Cypress Island. Not bad for my first ever cruise...
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Chachere
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   We've had this problem more than once; indeed, anytime we find ourselves unavoidable passing through a large patch of seaweed we put the engine in idle (to reduce the water intake) and try to "coast" through it, and if we notice a reduction in the water flow coming out of the muffler after we've gone back up to speed we stop and check the strainer, and sometimes had have to pull the hose off the seacock to make sure its not clogged.   Poking a stick through will usually clear it.  
   Tom Soko's catalog of his improvements to his former C36 included a nice set-up he installed, with a T directly above the seacock so that simply unscrewing an end-cap would give access for this:  https://julandra.shutterfly.com/240  (We've copied most of Tom's smart improvements on our boat over time, but confess we haven't gotten to this one yet).

Barber
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Indeed while motoring home just after fixing the original issue we went through several green patches and wouldn't you know it, we sucked some greenage again which resulted in restricted intake flow. I'm way more cautious now.

At least on my boat you can test whether the seawater intake is working fine by using the sink foot pedal and watching how much water you get. Adding a T is a great solution. I'm also thinking about having a small air compressor set up that I can use to blow air through the seacocks.  

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Chachere
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I have read in several sources (Calder, others) that sharing the engine's raw water intake with other uses should be avoided (as apparently your boat is set up with a salt water supply to the galley sink tee'd from the engine).  Might be a good idea to supply it from a different (but existing) seacock.    Just a thought (I'm not an engineer, so this is definitely one of those FWIW opinions!)

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Catboat Willy
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Hector; Glad you got that rectified with a simple solution to the problem. We've been following your progress here.
Bill

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KevinLenard
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Note that Firefly ran at between 180-190 degrees with no issue for many years.  190 is not out of spec.  She's now jumped up to 220 if I rev her over 17,000 RPM, so I have to identify the issue (boiling water out of the taps isn't pleasant!).  After checking water flow through the exhaust at idle vs. throttled up it's clear is it not an impeller, or through-hull/strainer, or burping issue.  The thermostat opens at 160 degrees in a pot on the stove with the meat thermometer in there.  The thermostat is installed the right way up. 

NOTE: I did try the Julandra T-fitting, but it seems there's no opening down through our strainer?

Seems the issue is within the 2 year old antifreeze coolant impeller and circulation, so draining and removing the heat exchanger is next on the agenda, soaking in CLR and seeing if anything comes out. 
 

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KevinLenard
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Well after trying many other things, all the easier things!, I took out the heat exchanger and found it filled with bits of black rubber from the old raw water impeller. Clean them all out and now it is running back at 165 degrees.

Barber
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Getting the heat exchange out is not too bad. At least you didn't have to deal with taking apart the exhaust...

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