3YM30 Overheating 21EC [2006]

[Murdock]

Any thoughts why my 3YM30 overheats (idiot light goes on with warning alarm) when RPM's exceed 2400 for longer than 10 minutes? One suggestion is that the filter mesh in the in-line Sea Dog strainer may be too fine ... believe it is 50 mesh.

Any/all comments welcome,
Brian

 

[SGIDAVE]

Any thoughts why my 3YM30 overheats (idiot light goes on with warning alarm) when RPM's exceed 2400 for longer than 10 minutes? One suggestion is that the filter mesh in the in-line Sea Dog strainer may be too fine ... believe it is 50 mesh.

Any/all comments welcome,
Brian

Hello Brian,

Sorry to hear of your overheating problem.

I've not yet had that problem.

A few questions:

Can you quantify the amount of raw water ejecting from the exhaust? As in "lots" or "so-so" or "not much"

What does your raw water impeller look like - that is, is it INTACT with all it's appendages? When was it last changed?

Recently, I noted poor ejection of water from the exhaust (on my 21EC) and slow initiation of water flow out of the exhaust after starting the engine...I changed the impeller cuz it had been a year. STill no better. I fussed around, checked impeller AGAIN and it was fine. A little more investigation and I discover the raw water pump BELT WAS LOOSE. How did that happen? IDK!!. Anyway, I snugged up the belt and she pumps like....a pump.

So, check the raw water pump drive belt.

I DO NOT think the fine mesh in the raw water strainer is the culprit...unless it is physically blocked/clogged. My 21EC had that strainer before I swapped it for a better one. I never had overheating problems.

How many hours on your engine? Has the exhaust riser been cleaned/replaced yet? If your boat is 2006 MY, it is certainly due. Prolonged idling (say less than 1600 rpm) is associated with carbon buildup in the exhaust riser water injection port. This serves to NARROW the port for water egress from the cooling system and would functionally act the same as a partially blocked raw water intake. My understanding is that the carbon buildup is rock-like and CANNOT be cleaned so the riser is preplaced as a whole unit. Pull off the raw water hose as it enters the exhaust riser and see how much crud has built up.

Let us know what you find.

Fair winds and warm-but-not-overheated-engines,

/david

 

[Murdock]

David,
Thanks for your thoughtful response. I will address your comments in the order you raise them ...

[I failed to mention that the 3YM30 has always overheated when run at > 3200 rpm. Only recently has it begun to overheated at higher than 2400.]

1) Exhaust = lots [has never seems to be an issue]
2) Impeller: routinely changed out; last time 2 weeks ago
3) Raw water pump belt was loose .... But it was replaced with a new belt 2 weeks ago and is snug
4) Raw water strainer not plugged ... checked with each use of boat. [QUESTION: why did your change strainer for a "better one?" What is the better strainer?]
5) New exhaust mixer-riser replaced one month ago.

I had hoped that with the above recent maintenance the overheating problem would be resolved .... but that is why they call them BOATS ...

Brian

 

[SGIDAVE]

Well then...we have quite a mystery on our hands...

I would attempt to clean the heat exchanger or in some way satisfy myself that it was adequately functioning.

THEN, I would replace the temp sender that is responsible for the "overheat" light coming on.

When your out, take an IR temp sensor gun, and take repeated measurement of engine temp. The center of the oil filter is a good approximation of engine time and gives you a consistent spot to measure.

My thinking is that if the cooling system is functioning properly, there should be NO OVERHEAT situations at all. You said it has always overheated when run at >3200 rpm (but now it happens at much lower rpm range, correct?). And, IF the cooling system is indeed working (new impeller, new exhaust elbow, strainer clear, good water ejection from exhaust, etc) then perhaps the overheat warning is an error due to a bad sensor/sender.

So, try measuring it yourself with the IR gun.

Regarding strainer, I replaced mine with a Vetus model that is now standard equipment on the 2014s (I think). It is the model 140 like this:

There have been incidents where the factory installed strainer cracked (from ice formation) and the boat sank at the slip; for safety min is now mounted ABOVE the water line to prevent this disaster. Anyhow, with the design of the Vetus model, you can immediately see if raw water is moving through the system. I like it! There is a pic of my installation in my photos album titled "Replacing Motorbox bulkhead and raw water strainer "

/david

 

[CAPTCRUNCH]

OR...

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[Murdock]

David,
Thanks for your continuing input. I will be taking Bessie's temp, as you suggest, during our next few outings and will keep you posted. If we can isolate the problem to the temp sender that would be a nice way to close a long standing mystery. Your "better" strainer, and your positioning of it, looks very interesting.

Regards,
Brian