Flushing seawater cooling system

[Windward mark]

My little yanmar ysm8 overheated and stopped last weekend so started investigating.

Found the impeller dodgy but with the weather getting decided it was a good time to pull things apart and check the general condition.

The engine starts well in warm weather but hard to start in winter, so I was thinking I could probably manage a valve grind, looking at YouTube it doesn't seem to hard.

I couldn't get the anode out so pulled off the top cover and found the anode was severely corroded and internally there is a build up of some sort of crusty substance (not salty)

So the question is, can I flush the engine cooling system somehow, I presume the hidden parts are just as bad if not worse.

While I'm asking for help, there is no resistance on the hand crank. I was going to pull the front off and try and see what's wrong.
Is there anything I need to be wary of ?

I haven't worked out to post photos yet, any tips 😊

Cheers, Tom

[hugosalt]

Any vanes missing on impeller, how was water flow?
Sounds like time for change in any case. Change mine every year, (3 Gm)
Yanmar recommends starting GM motors in cold weather with throttle at 3/4 then
when started throttle down. Check your manual/on line if same for your motor.
Yes can flush, do my 30 year old raw water cooled every couple of years using Rydlyme,
check Mainesails procedure follow step by step.
Also have you checked your mixing elbow for blockage.

[Windward mark]

Mixing elbow was clean. Looks like it has been replaced in last couple of years ( mine for 15 months)
Impeller fins were ok but it looks like the cross piece in the centre was turning without the fins.
Will check it the Rydlyme site, thanks

[hugosalt]

If your center piece (core) of impeller turning and not fins...then fins have separated and
no water is flowing/cooling motor. (i have had this happen) Did you not have alarm go
off when you overheated? Change impeller and hope no damage done...and check alarm.
I would change oil but maybe maybe mechanics on forum can advise further...

[Lepke]

Most diesels start harder in cold weather. The issue is heat generated by compression isn't enough for ignition. Glow plugs, block heater, etc., the usual ways to help cold starting. Glow plugs can be added to engines that don't come with them. Valves are not usually the reason for insufficient compression. Piston rings contract with cold and inactivity and re-expand after starting.
I also use Rydlyme .

[lockie]

Diesel starting is all about compression. Got it, start ok. Not got it, hard to start warm or cold. But having said that some throttle in cold weather is pretty important even for a good engine.

Re flushing, I fill the CW passages (not the pump) of my 2GM with cleaning vinegar when I do the annual service and leave it for 24 - 48 hours. I'm always amazed by the increase in water out the back, even though it's been running fine and not overheating even when flat out. This year I also I reverse flushed for about an hour using a drill pump to circulate the vinegar. Cheap as, very effective and safe to pump straight out.

I also have had an impeller slipping on the shaft. Never with a Yanmar brand one though.

Cheers, Graeme

[SkipMark]

Here's a good step-by-step guide:
Flushing a sea water cooled Diesel - SailNet Community

[Compass790]

Hi Tom,
i have a YSM8 with low compression ( badly worn bore) & it wont start when cold without using full throttle. Have the same problem with hand crank but couldnt see anything obvious when I had front case off but didnt spend any time investigating the problem. No problem to get front case off from memory but try & save gasket unless you are wealthy. Vinegar only dissolved a little of the deposits on a test head that I tried, sounds like rydlyme will be much more effective, I'm soon going to test sulphamic acid as a descaler on my junk head. If you are in a marina you can rig up a system to fresh water flush each time after a trip & we've found the anode lasts much longer doing that. Yes doing a v/v grind is easy, just be careful you dont knock the pushrod down into the sump( ask me how I know)
Have done most engine repairs on ours including rebuilding injection pump & injector, crank grind, machining up new big-end bearing, welding con-rod so if you want any info you can message me. I use aftermarket parts from Taiwan as the Yanmar prices here are very high i.e would you believe $630 for a conrod? Found the engine work to be pretty simple if you have the workshop manual. Noisy shaky beasts but pretty bulletproof design as long as they are maintained properly. Only fatal flaw I can see is the exhaust elbow design & construction material as when it leaks it drops salt water on the exhaust v/v.

[Cheechako]

Leave a 100 watt bulb next to then engine in winter. Makes it much easier starting.
Vinegar wont tou8ch that corrosion buildup. You need something stronger.

[lockie]

Originally Posted by Cheechako

Vinegar wont tou8ch that corrosion buildup. You need something stronger.

That's right, vinegar won't dissolve corrosion products if you neglect your anodes, nor the hard salt accretions after you overheat your engine.

But it will clean out most of the deposits that build up during normal running. My eyes don't lie - I see a considerable increase in CW flow.

For a product that is totally safe, and available at the supermarket for a couple of bucks vinegar is pretty good.

Cheers, Graeme

[Cheechako]

Soaked the heat exchanger core from my Yanmar for 2 days just to get rid of very minor white debris chunks here and there. No change at all when I took it out of the vinegar. Might as well have used water.
Used vinegar in my toilet often to keep the buildup in the hoses out. Removed those hoses to replace and they were well filled with the buildup.
Frankly I haven't found Vinegar to do it on much at all.

[01kiwijohn]

I run a product, from West Marine, called Saltaway, through my (3GM 30F)heat exchanger raw water side a couple of times a year. Just had the exchanger serviced and it did need cleaning out, and a developing crack in a soldered joint repaired, but was otherwise fine after 13 years. On my previous Volvo I initially pumped a continuous flow of a similar compound through it for a couple of days. After that, I'd fill the system with vinegar (old Volvo mechanic suggestion) and let it sit for about a week, twice each year; trouble free after that.
Hard starting in cold: At the dock, I use a hair dryer and shoot it into the air intake. >1500 watts, works like a charm and no danger of damage as you would risk using ether.

[Arthur Garfield]

Cheap dip stick heater to improve staring when cold if no glow plugs.
Scale buildup quite common.Quick google search will help find good cheap scale dissolver and part soaking will do the trick.
As for pump free spinning-sounds like impeller needs replacing.


All the Best

[jacktheflyer]

Originally Posted by Compass790

Hi Tom,
i have a YSM8 with low compression ( badly worn bore) & it wont start when cold without using full throttle. Have the same problem with hand crank but couldnt see anything obvious when I had front case off but didnt spend any time investigating the problem. No problem to get front case off from memory but try & save gasket unless you are wealthy. Vinegar only dissolved a little of the deposits on a test head that I tried, sounds like rydlyme will be much more effective, I'm soon going to test sulphamic acid as a descaler on my junk head. If you are in a marina you can rig up a system to fresh water flush each time after a trip & we've found the anode lasts much longer doing that. Yes doing a v/v grind is easy, just be careful you dont knock the pushrod down into the sump( ask me how I know)
Have done most engine repairs on ours including rebuilding injection pump & injector, crank grind, machining up new big-end bearing, welding con-rod so if you want any info you can message me. I use aftermarket parts from Taiwan as the Yanmar prices here are very high i.e would you believe $630 for a conrod? Found the engine work to be pretty simple if you have the workshop manual. Noisy shaky beasts but pretty bulletproof design as long as they are maintained properly. Only fatal flaw I can see is the exhaust elbow design & construction material as when it leaks it drops salt water on the exhaust v/v.

I'd be interested in your supplier in Tiawan?

[Windward mark]

That's all very encouraging, all the work is being done on a mooring so a bit tedious at times.
From searching on line the hand crank appears to connect to the flywheel via a chain not unlike a bicycle.
Currently have the old anode soaking and hopefully will eventually get it out.
My list of replacement parts is growing and would appreciate the name of your supplier to keep costs under control