High Temp alarm

[catchersrock]

Guys

I was out at Cape Lookout last weekend and on my way in on Sunday afternoon my high temp alarm went off. I immediatly shut off the engine and tried to diagnose the problem, but, was unsuccessful. I let the engine set for 4 or 5 minutes then cranked it back up and no alarm, so I took off. A few minutes later it alarmed again. Long story short, against an outgoing tide, I fiddled with it, run - stop, run - stop, no luck. I then let it set for 10 minutes, restarted, no alarm, and I hammered it. As long as I stayed on it, the alarm would come on intermittenly then go off. If I slowed for a buoy turn, the alarm would be steady. I did this for maybe 10 to 15 minutes to get back to the ramp.

Once on the trailer, I found the pee hole had sand it it. Duh!

I ran the boat at the lake yesterday and it ran fine.

Do you think I have done any damage? How hard can you push the alarm, how long? Do I need to do anything now, maybe a compression check?

Thanks,

[gnrphil]

Sounds like it's water pump time to me, the pee hole does nothing but indicate water flow has no effect on engine cooling. You mention sand, could that suggest you sucked up some sand through your water pump and damaged it ?

[catchersrock]

Mar 29, 2017 8:43:15 GMT -6 gnrphil said:

Sounds like it's water pump time to me, the pee hole does nothing but indicate water flow has no effect on engine cooling. You mention sand, could that suggest you sucked up some sand through your water pump and damaged it ?

So, plugging the pee hole should not in itself cause the high temp alarm?

[gnrphil]

No, all it's for is a visual check for water flow. Sounds like your pump is giving enough flow at higher rpm's but can't push as much at lower rpm's, I'd pop a new one in and see how it goes. Do you know the last time it was changed?

[catchersrock]

Mar 29, 2017 9:17:14 GMT -6 gnrphil said:

No, all it's for is a visual check for water flow. Sounds like your pump is giving enough flow at higher rpm's but can't push as much at lower rpm's, I'd pop a new one in and see how it goes. Do you know the last time it was changed?

Thats the most frustrating part, I had it at a Certified Mercury Service Center 3 months ago for a full service including water pump replacement.

[985crabs]

I'm thinking if your pisser isn't pissing, your piss is being internalized and heating up to an uncomfortable temperature. Cooling is accomplished by heat exchange between the block and the water flowing through the system. If that water remains hot the block can't exchange enough heat and it will heat up. Hence, the alarm. My theory anyway.

I did the alarm, shut down, restart, alarm, shut down, wait, restart, etc. scenario crawling through some shallow water. When I got into clear deep water and the alarm was silent I hit it and got on plane. My Optimax threw a rod 30 seconds later. No more Optimax.

I did this because I had the motor to the mechanic twice for this mysterious alarm and he could not find anything wrong. I thought my motor was crying wolf. I waited until it stopped and then proceeded, but maybe the alarm was telling me something important after all. Alarms are there for a reason. They've been known to be faulty, but most often they are not. I'd use extreme caution.

[freezerfiller]

I would replace the impeller. Sand may have blocked the pee hole, but it came through the water pump and would also sand down and reduce the flow that the impeller can produce. I had the same issue with my Johnson, and it doesn't get better. It may be fine at high speed, but at trolling speed, it will happen again. My $0.02.