Overheated

[Seabee Chief]

After changing our head gasket a few months ago, everything was running great! Yesterday the temp was normal until we were coming into the channel and I saw the temp gauge was buried at 225. I couldn't shut her off in the channel so I made the commitment to putt up to the fuel dock. (the first dock in the marina) It was a short 200 yards up the channel. As soon as I cut the corner I throttled down and she stalled about 50 yards from the dock. I was able to coast in and the dock hands were able to stop me with spring lines. Close call! I got a tug over to my slip. It could have been worst.
I didn't have time last night, so this weekend I plan to start working the problem by the numbers. First thing will be to check the strainer for blockages. Then check the impeller. I have never checked either since obtaining the boat last fall. If both check out OK, what else would cause the sudden rise in temp? When we changed the gasket we flushed out the engine really good. Is it time for the fresh water change over? Would it have mattered?

Chief

[Administrator]

You could have sucked some debris (plastic bag, etc.) up against the thru-hull intake which would have shut down the flow of water. This may have fallen harmlessly away when you shut the engine down, or not.

Key question: Were you discharging cooling water out the transom when you overheated? That will tell you a lot.

Bill

[ndutton]

If you have a blockage or failure in the raw water circuit, FWC won't make a difference. Were you shipping water out the exhaust? That would be a clear indicator right there. On my C-30 I can hear the water splooshing out the transom all the time, I particularly listen for it. When it doesn't sploosh (only once since I've owned her) the exhaust echos.

edit: I see Bill was typing at the same time as me.

[Seabee Chief]

Thanks for the quick responses.
There was no water coming out of the exhaust.
I think that's what made me look at the temp gauge in the channel.

[sastanley]

Fire her up at the dock and see if she splooshes water now...if so, I'd agree with Bill..a momentary blockage...if not, then we have a failure somewhere.

[Seabee Chief]

Will do. I will let you know how I make out this weekend. One thing for sure, I am going to install that MM alarm kit I purchased a few months ago.
One thing with the alarm kit, currently my blower only works when the key is on. If I hook up the alarm kit as is, the alarm will sound the whole time I am purging the engine compartmant. Shouldn't I re-wire the blower right from the battery? Will I have any problems doing this?
Chief

[roadnsky]

Will do. I will let you know how I make out this weekend. One thing for sure, I am going to install that MM alarm kit I purchased a few months ago.
One thing with the alarm kit, currently my blower only works when the key is on. If I hook up the alarm kit as is, the alarm will sound the whole time I am purging the engine compartmant. Shouldn't I re-wire the blower right from the battery? Will I have any problems doing this?
Chief

Chief-
No problem hooking it up that way.
Many boats (including mine) are wired with the blower on it's own circuit switch.

[sastanley]

Chief,

Re: blower wiring. Yes..

You simply need to move the +12v that goes to the blower switch over on the key, which is where I suspect it is currently wired. It needs to move to the terminal on the key that is hot all the time, instead of the "On" position. I just wired up a voltmeter in the cockpit that I only wanted to work with the key on & I noticed how the bilge blower was wired...I would NOT want the blower wired to the "on" position..you are burning up your coil & points/ ignition when running the blower before starting.

Do you have a separate on/off switch for the blower? Mine is a pull/push switch right next to the key in the instrument panel.

[Seabee Chief]

Yes I do have a separate toggle switch next to the key for the blower. I also have another small bank of swiches in the cabin that allows power to the cockpit. I believe when these are shut off, it will also cut power to the blower, so no one will accidently turn it on.
I will have to check it out this weekend and do some tests.
Chief

[Seabee Chief]

Update

This weekend we inspected the sea strainer and it was clear.
Then I pulled the back plate off the water pump and inspected the impeller.
It also looked great. I turned it over while my wife watched the impeller turn.
It seemed to be working properly. I replaced the back plate and started the engine. Water started coming out of the exhaust after a short period of time and the temp began to rise. My thermostat should open at 140. After the temp was up to 190, I shut it down. I now believe this is my problem and have ordered a replacement from MM. I'll let you know how we make out.

[ArtJ]

Before giving up on your current thermostat, try putting it into a jar of
vinegar for a day or two. Most thermostats respond favorably to this
treatment. Especially if you have one of the Bronze holley three spring
thermostats which Don Moyer raves about, you would want to save it.
you can test with hot water on your stove and see it opening and
closing after cleaning.

Regards

Art

[ndutton]

Seabee,

If you haven't yet, you should read these recent threads regarding replacement impellers:

http://www.moyermarine.com/forums/showthread.php?t=4038&highlight=short+impeller

and

http://www.moyermarine.com/forums/showthread.php?t=4222&highlight=short+impeller

The attached picture has the labels reversed but it clearly shows the problem.

and Baltimore, what ever became of your related issue?

[Baltimore Sailor]

My issue hasn't gone away, or been fixed. I'm just using my old impeller for the rest of this season, and plan on replacing the water pump over the winter.

Actually, I've been having overheating problems lately -- I can't run at full throttle without it moving up towards 200 F, so I keep it at 1500 rpm and she runs steady at about 190 or so. I think I've got a bunch of growth on the bottom, but I can't find anything flexible enough to run down my through hull to try to clean it out. I'll be getting her powerwashed soon, so hopefully that'll take care of it. I also plan on doing a power flush as well.

[Seabee Chief]

Art thanks for that suggestion.
When we changed the head gasket a few months ago, I did flush it out good and tested the thermostat. It was tarnished but tested fine. I will do the vinegar and test it again. If it works, I will keep it as a spare on board.

Neil,
Great threads, thanks.
Next season I plan on replacing the impeller and add the MM Back Plate to the pump.

Thanks again for the replies.

Chief

[Seabee Chief]

Temp

BS

Mine also will not get up to full throttle. I usually run at 1800 RPM with 150 deg and get around 6 knots depending on the current.
This may be a good question to take a poll on.

Chief