Temp Warning - YSM8

[Warren Kaplan]

I had a curious experience yesterday when ending my sail. I had the tillerpilot engaged and steering my CD27 at a slow forward speed as I went forward to douse my mainsail before heading for my mooring. As I was bring down the sail I heard an alarm go off and I dashed back to the cockpit to see the red light lit for the engine temperature. I throttled the engine back and the light immediately went out. I motored about a mile at slow speed, a good 15 minutes and the warning alarm never came back on. After I tied up I put the engine in neutral and gunned the engine for while, then let the engine run at a lower speed a good 15 minutes. The light never came back on and water was shooting normally out of the exhaust at the transom.
A couple of things you should know:
I checked the engine compartment and the water seacock was open. There were no ruptured lines and nothing looked amiss. I had run the engine at higher speeds earlier in the day.
About 2 weeks ago I had the mechanics at the yard, all quite good, change the raw water impeller and generally go over the engine. I've run her two other times this season with no problems whatsoever.
Is it possible that perhaps something temporarily blocked the raw water intake when I was motoring slowly and that caused the temp to rise until the obstruction cleared? I think if it was anything else, other than some sort of electrical fluke or short, the engine would have continued to overheat as I continued to use the engine. I ran that engine at least a half hour after the alarm went off and the light never turned on again and the engine never faltered or struggled. I think it would have if there was an ongoing problem.
Any ideas??
Thanks.

[Kurt]

Warren,
If a normal amount of water was shooting out the exhaust, then you can rule out the raw water impeller or a plugged intake. The overheating you experienced could be caused by a bad thermostat or possibly a water passage is plugged up inside the engine? Or it could be a bad temp sensing switch. The raw water cooled YSM8 is about as simple an engine as you're going to find in a boat, including its cooling system, so trouble shooting the problem shouldn't be too difficult. You mind consider installing a temp gauge which would allow you to more accurately monitor the actual temperature of the engine.
Hope this helps,
Kurt

[Warren Kaplan]

Kurt,
Thanks....it does help. The confusing part to me is why it didn't "overheat" again when I ran it for an extended period of time. Perhaps it is a faulty sensor or something along those lines. I think I'll motor her around for a while next time out and stay close to the mooring to see if it happens again.

[Bill Chapple]

Warren, I have had this problem on occasion on Pagoo, our CD 27. I believe that it is a temporary blockage of the raw water strainer because I don't see water coming out of the exhaust. Shutting off the engine and waiting for a bit often helps; when you start the engine again, it runs normally. It may be that the shape of the strainer makes it prone to this kind of problem. To reduce this blockage, before she goes in the water, I use a drill to clear the paint that has gotten onto the strainer, as well as small organisms (bryophytes, hydroids, etc) that have taken up residence in the strainer. Hope this helps

[Warren Kaplan]

Bill,
After I throttled back and the alarm stopped, I figured maybe something, a plastic bag etc., got sucked up against the strainer and blocked the water intake. Honestly I didn't see at that very moment whether the water was coming out of the exhaust. All I know is that when the alarm quieted down and I got my wits about me, maybe 30 seconds later, I did look over the transom and there was a good stream of water coming out of the exhaust port. I ran the boat a good 30 minutes steady after that and the alarm did not engage. I suspect a temporary blockage, or maybe a problem with the sensor and/or wiring. I didn't see any leaks around the engine plumbing. I'll just have to see if it happens again. Hopefully not. It could be bottom paint in the strainer. The yard painted and dunked the boat before I could see the bottom. I've had to take toothpicks and clear the holes in some previous years. So who knows!
Thanks!

[bilofsky]

When my (larger) engine started overheading, the cause was a corroded exhaust elbow. Another possibility could be dirt anywhere in the cooling system, though that's more likely in a powerboat like mine.

The first clue is whether it overheats again at the same revs.

[JimKortleven]

Hi Warren,

I had a similiar problem yesterday. First I checked my seacock. Ran the motor with the hose in a bucket. Still alarm. Changed the thermostat. Still alarm. Was about to go for the impeller, when I noticed my belt was loose. Two 13mm bolts and a flathead solved the problem. Coulda shouda woulda.........Next time I'll check the belt sooner...

[Warren Kaplan]

Hey Jim...how are ya' Hope to see you once again out on the Sound either near City Island or around Oyster Bay!
Thanks for the advice about the belts. I didn't do that the other day but its the first thing I'll check this weekend!
Thanks again!!

[Warren Kaplan]

I was planning on going sailing today but it is rumored that you need wind to accomplish that. I didn't get any today even though I motored around for almost two hours looking for it and getting to and from the mooring. In any event, as I said, I motored for 2 hours and the engine worked to perfection ...uh..for a one lunger. Jim, the belts seemed to me to have the right tension and there was no oil coating etc. So, perhaps it was some sort of "temporary" plug or a gremlin in the sensor. Hopefully it won't be necessary to find out.