Delayed Cooling Water Exhaust Flow

[goodintheory]

My Pearson sailboat runs a Yanmar 2GM20 that's cooled with raw water.

Here's my problem: upon starting the engine, water usually starts flowing out with the exhaust. After a few minutes post-start, it STOPS flowing out of the exhaust. Then after several minutes (and tweaking up the throttle a bit) water starts flowing out the exhaust again. I thought that this was normal (i.e. I thought a thermostat regulated flow of cooling water) until an overheating light and alarm went on the other day when water wasn't flowing out the back. While returning back to the marina, of course, after a "burp" exhaust water started flowing out, the temp came down and the alarm/light went off. It doesn't seem like a blockage since once it burps, water flows with the exhaust like there's no tomorrow. Here's what I'm going to do but I'd like to know if I'm missing anything:

1) Check raw water seacock and ascending piping to pump
** Raw water strainer is not the issue
2) Replace the impeller
3) Clean antifreeze/coolant reservoir
4) Cycle and replace the antifreeze/coolant
5) Replace the thermostat

Any suggestions or past experience with a similar issue?

Thanks!

 

[rhythmsurfer]

Do you have a heat exchanger? If so try cleaning it with muratic acid. I did this and there was an amazing difference.

 

[alexco38]

"My Pearson sailboat runs a Yanmar 2GM20 that's cooled with raw water. " Raw water cooling doesn't have heat exchange.

If your strainer is above water line, you'll have to shut off seacock, fill the basket with water and seal the lid and then open seacock. Air is in the system.

 

[Steve Dion]

Do you have a heat exchanger? If so try cleaning it with muratic acid. I did this and there was an amazing difference.

He must have a heat exchanger if he checked to antifreeze!

 

[goodintheory]

Good thoughts. Every time I've accessed the basket to clean the strainer it's been filled with water and was filled to the top with water when I closed it. Do you think that a little air in that hose ascending to the pump from the basket could be the source of the problem knowing that as soon as that kingston cock (seacock) is opened, water will be pushed toward the water pump and impeller? I guess maybe if backward pressure from the engine to the pump was greater than that of gallons of water surging through the seacock to the pump, but it seems too simple. . .

 

[kloudie1]

replace hose between kingston and strainer.. and between strainer and pump.. be careful to tighten all of the cooling water the hose connections downstream of the pump too, .. Sounds like you have a very small air leak which is letting air into the system and the pump is losing prime and has to pump the air out then re-prime and pump water. Check the strainer gasket (s) carefully..

 

[rhythmsurfer]

Claude has a good point. I had that problem with the AC.

 

[zeehag]

mixing elbow. how old is it--they need changed out every 5yrs or so because they get clogged or rusted and dont work. this is per my yanmar man--i have a 2qm20h in that ericson i still own. check it. i know someone who cleaned his and used for another entire season..i sailed with him in gulf. smooth sailing.

 

[goodintheory]

Thank you everyone for your suggestions and contributions -- I sincerely appreciate it. The problem has been solved. Since I bought the boat a year ago, I figured a few minor replacement parts would not be a bad thing to bring me to a baseline since there's no telling what the PO did or did not do. So here's what I did (with some lessons learned):

1. Replaced the hose ascending from the strainer

LESSON: Do not use a standard 80# 5/8" heater hose from a hardware store. Not because they can't handle the temp or pressure but for one reason: they kink.

2. Replaced impeller + gasket. This was not the problem -- my impeller looked fine. I have a new one in there now, and "now I know".

LESSON A: This job is a cinch. If you suspect an issue with the impeller or its coming of age, do it.

LESSON B: I had a screw strip because it was screwed in too hard and had to be drilled out. Another reason to do this according to spec'd frequency.

LESSON C: Check the tension on the water pump belt on occasion -- there should be less than 1/2 inch of play.

3. Replaced the hose ascending from the water pump to the engine block.

LESSON: You NEED to use the OEM Yanmar part because of the curves on the hose that fit the engine. Generic heater hose will not work (see fix #1).

4. Replaced the U-mixing exhaust elbow, exhaust elbow, joints and gasket from the manifold. I took zeehag's advice and checked mine out and it was rusty and covered with carbon inside. It was suggested to let it soak in muriatic acid for a couple of days and then clean it out, but I would rather hedge my bets with a new part despite the cost.

LESSON: Very few mechanical repairs are cheap.

LESSON B: Large open-ended plumbers wrenches are worth their weight in gold.

LESSON C: Spin the joint on the mixing elbow and exhaust elbow at the same time to ensure that the joint is fitted equally into both pieces (a reverse thread facilitates this). I did this off the boat using a clamp.

5. Ensured that all hoses are clamped tightly and are airtight.

LESSON: These hoses are tight. I used Windex to lube them a little to get the hoses on the fitting.

6. Flushed all old coolant/anti-freeze out of the system three times using the two (2) drains on the side of the engine block, located immediately above the oil dipstick -- using three gallons of distilled water.

LESSON LEARNED: Yes, there is a cooling water draincock on the right side of the Yanmar 2GM20F (facing forward). There are two, actually.

7. Replaced the engine and system with red, Yanmar spec'd coolant/antifreeze.

LESSON LEARNED: Ensure that your system is flushed of the old stuff (I had green in my block) before replacing with a different color.

Upon starting, the Yanmar started spurting water out with the exhaust and never stopped. No clogs. No air pockets. No hesitation.

Thanks again everyone.

Chris

 

[kloudie1]

Good job ! and now ya know it is good !