Started to run quite hot

[Sculldog1]

Hello folks, I have a raw water cooled engine that runs quite well and usually at around 160 or so consistently for a couple of seasons. This season the engine has begun to run quite hot (approaching 200). I plan to replace the impeller this weekend but also hoped to get a plan for troubleshooting the issue should the impeller replacement not cure the trouble. Any advice or thoughts appreciated. Thanks

[JOHN COOKSON]

SOME IDEAS

A good summary test is to attach a hose to the manifold outlet barb, start the engine briefly and rev it up. Should be like a garden hose in output. Only do this momentarily since there will be hot exhaust in the exhaust system with no water going through it.

Before changing out the impeller you could try clamping the bypass. This will force all the cooling water through the engine.

Do you have a thermostat? The thermostat may broken and stuck in the closed position. If you have one of the three legged, two stage thermostats it might not be blocking the water flow from the bypass as the engine heats up.

There may be blockage at the intake before the water pump. Pull the inlet hose off at the water pump and check for good water flow.

How long since the last acid flush? The water passages inside the engine may have a lot of KRAP in them.

Also, as you noted, the water pump output may not be up to par.

ex TRUE GRIT

[Al Schober]

Surprised John didn't mention it, but check the outlet elbow from the manifold. Also, remove the thermostat until you get things under control.

[Sculldog1]

Thanks to all.

Sorry for not replying to your helpful posts sooner guys. I haven't had much time to get out to the boat as weather has been bad and some overtime at work. So far I have proven good water flow and condition of water pump impeller is good. I will be removing the tstat and checking for good flow exiting the manifold next. I have a feeling I need to do an acid flush as, although I cleaned water jacket as well as I was able to last winter when replacing head gasket, I think there may be some restrictions on the exhaust side of things. Will update my progress and efforts for either helpfulness or comic relief. Does acid flush require fresh water or will sea water work just as well? Asking because I am on a mooring and rowing to and from like Gunga Din with fresh water buckets no fun if sea water ok. Thanks

[Dave Neptune]

Perhaps try a vinegar soak first, very easy and letting it set for a couple of days can work wonders in many cases. I suggest this since you replaced the head gasket and cleaned the cylinder walls recently.

Before starting procedure shut off the water intake valve!

1 remove thermostat.

2 remove water hose to block hose to drain the block.

3 connect hose to block T fitting that will extend above the engine.

4 disconnect hose from EXIT port

5 fill highest hose with VINEGAR until it dribbles out the other hose

6 let sit 3-4 days

7 reconnect and start without thermostat, let her run at high idle for a bit

8 check EXIT fitting on manifold for loosened debris. If clogged repeat until no clogs.

The worst thing about dealing with the vinegar is the boat will smell like a salad.

Dave Neptune

[Sculldog1]

Thanks Dave. I will try that this week. I did do a vinegar soak like that after getting cylinder. head gasket squared away prior to last season and she ran consistently around 160 all last season. Winterized as usual and everything seemed aok first couple times out then she began running hot. A question though is ho come you prefer vinegar to muriatic acid flush? I figure vinegar in my case be good as it difficult to capture outflow while at the mooring but the effectiveness comparing each? Much obliged to all for the assistance.

[roadnsky]

A question though is ho come you prefer vinegar to muriatic acid flush? I figure vinegar in my case be good as it difficult to capture outflow while at the mooring but the effectiveness comparing each?

Vinegar is much easier to use and is a more "forgiving" acid.
It also isn't bad for the environment if you let it flow out the exhaust into the surrounding water.
As Dave said, try that first, because it's a lot easier to do and if you're still having a cooling issue, you can move up to muriatic blasting.

FWIW, I think you just have some crap clogging up the works.
Very likely at the manifold like Al suggested.

[Dave Neptune]

The vinegar is a much less caustic acid and does not attack the iron and steel nearly as much as the "acid wash" does. The "acid" will remove some block material while attacking the KRAP in the block. It is also necessary to take far more caution in handling the acid. The plus side to the acid is it is much faster.

I would surely try the vinegar first as you are on a mooring and carrying the acid back and forth to dispose of it will be a mess. With the vinegar just hook up the hoses and start her. With the acid a good flush and/or neutralizing may also be necessary as you don't want it to sit for long at all.

The acid does work better however it may not be necessary. I did an acid wash on my A-4 once as it was really bad and for the next 30+ years I did a vinegar soak every 3 or 4 years just to keep thing inside clean. Never had a heating episode except when I sucked up a bag in the water intake.

I also never used the t'stat and ran around 130~140 all those years!

Don has developed a new t'stat for the A-4 that many are very happy with however I sold my A-4 just after it was developed.

Dave Neptune

[Dave Neptune]

Pt II

Did you check your t'stat to see it is fully open at the specified temp in a pot of water with a thermometer?

Dave Neptune

[Sculldog1]

I did do that at the time of head gasket job. Cleaned tstat right up by vinegar soaking first then heated it up in pot of water with thermometer in it and it opened up at about 160 if I remember. Will do the vinegar soak, clean and check tstat again and also check manifold for restrictions over the week ahead and hopefully get to the bottom of things. As always thanks for the help.

[Sculldog1]

Vinegar soaking worked very well.

Thanks to all who weighed in to help with the over heating issue. For to possibly help others I will report.

I filled the engine with as much white vinegar as it would hold after removing the thermostat. It soaked from Monday till Thursday. After starting the engine it had a greatly increased flow and chugged out a lot of grey/whitish goopy water that cleared up after a few minutes and when I revved the engine up to 2500 RPM more nasty stuff came out until finally completely cleared up. After running in gear against mooring lines for 20 minutes at
1800 to 2000 rpm the temp never exceeded about 130 degrees. It seemed cool but considering water temp still around 63 degrees and no thermostat it made sense.

The thermostat that had been in had a good deal of crud on it and did not move smoothly and as the P.O kindly left me a brand new one I will install it next chance I get and report on things after that. I call this a successful fix and hope anyone with similar issues may find this useful. Thanks for the vinegar tip and the saladsmell aint so bad. Happy Father's to all the Father's on the forum. Mike

[roadnsky]

Mike-
Soak the "old" cruddy thermostat for a day or so in pure vinegar and you'll be surprised how much it cleans up.
Then for some fun, boil it in a pot using a meat thermometer to see what temperature it opens/closes at.

WARNING: Do NOT use one of the Admiral's best pots for the test!!!
DAMHIKT...

[CalamitySC]

Inconsistent temperature spikes

HI all, I have found your tips and discussion very informative. I had one question to one of the comments made. Can you run your atomic 4 without a thermastat?

[Dave Neptune]

CalamitySC, yes in fact most of us do run without a t'stat and control temp with the "bypass valve". I ran this way for over 35 years.

Also MMI (Don and a few members) developed a new t'stat to replace the old a no longer available Holley t'stat.

Do remember that these are special t'stats because they don't just open they open the passage and close off the bypass at the same time so an automotive style will not work.

Oh and welcome to the MMI Forum!

Dave Nep[tune

[JOHN COOKSON]

If the "inconsistent temperature spikes" continue to be a issue let us know. A new thread would be the best way. To start a new thread scroll down on the forum home page to "discussion topics", and click the appropriate category (in your case "cooling system"). The start a new thread button is on the upper left.
Of course we will need more detail such as is your engine RWC or FWC, the range of the temperature spikes, does it happen when the engine is hot or cold or both, so on.
Been around this mulberry bush. Turned out to be a sending unit problem in my RWC engine.

ex TRUE GRIT