View Full Version : Overheating at idle

07-30-2007, 11:43 AM
I dropped my boat in yesterday and the temp shot pass 160 as i idled out. I shut it off and let it cool down. Started it up and took off towards the ramp, the temp quickly dropped back to 160 then started climbing when I dropped back to idle as I got to the ramp.

The questions:

I am getting ready to order a new impeller and t-stat. (these need to be replaced anyway). Is there anything else I should add to the order?

Also, on Saturday as I was getting the trailer and my wife was in the boat. After getting the boat out, she mentioned that the boat was running "rough". We had to get home so I didn't give it much thought. It had run fine all day. But now I am concerned that the boat was overheated as she waited for me. I don't know if she had the boat on the whole time, but I did see her idle back an forth a few times (it took about 45 minutes to get a ramp). What damage should I look for? what should I be concerned about?


07-30-2007, 12:01 PM
Hi Kirk,

Have you checked the water pump? A similar situation happened to me. As a result, I replaced the water pump and it has worked great ever since. Just a thought.


07-30-2007, 12:03 PM
I would suspect the impeller more than the thermostat. If the 'stat was stuck open, it would run cold. How long since you changed the impeller?

Running rough could easily be RPM reduction. It's dangerous to run a boat with raw water cooling when this happens because there's usually no cooling water coming in, which means that motor failure (melt-down) is very possible due to people trying to "limp home". Never run it if this happens unless your life is in danger. A car has a closed cooling system, most boats like these don't.

I would also check the oil cooler for debris. Weeds, twigs and plastic bags are a good way to cook a motor.

For the others who never check their oil coolers- read your manual- this should be checked before going out and would prevent a large number of problems.

07-30-2007, 02:20 PM
I haven't opened it up to look at it yet, but I suspect it is the impellar, been over 150 hours since last change. I never have replaced the t-stat, so I figure now is as good a time as any.

I am mostly concerned about damage from my wife idleing. After the boat overheated on me, I asked her if she noticed the temp gauge at all. She said she never thought to look at it. Temp was at about 190 when I killed the engine to let it cool down. I don't know how hot it may have gotten with her driving.

Anyone else notice that women in general don't pay attention to all those gauges. When I drive a car or a boat, it's just part of my routine: every couple of minutes I glance at them to make sure everything is OK. The only thing my wife looks at is the speedometer and the fuel gauge. I don't think she would even noticed if oil pressure, voltmeter, and engine temp were missing.

07-30-2007, 03:10 PM
When you replace your impeller, make sure to inspect the old one you pull out. If you see chunks missing, you will need to fish them out. I believe there is a screen in place toward the tranny side that is designed to catch the bits and pieces. If go to you replace your impeller and see that the old one is fine, check for debris in the inlet to your pump. If there are pieces of lake (weeds, leafs...) this could also cause this issue.

TX.X-30 fan
07-30-2007, 03:29 PM
I can't see that 190 would do any damage, some auto's have 190 thermostats. Mine did the same thing a few weeks ago. It was debris from the floods down here. First thing to check before the Impeller is the tranney cooler screen, mine had gunk all over it.

Edit: sorry JimN has that covered. I will ck mine from now on, I clamp to loosen and your done very simple for peace of mind.

07-30-2007, 03:37 PM
A friend of mine had the same problem last week. Their was weed is the oil cooler.

Cleared the weed out problem solved

07-30-2007, 10:38 PM
It's not the 190 degrees I'm worried about, its when my wife was waiting on me to back the trailer down and she never looked at the temp gauge.

I pulled the impeller tonight and it was toast. All of the fins were gone. I cleaned out all the lines and spent a good while fishing all the bits from the oil cooler.

07-30-2007, 11:02 PM
Impellers are odd things- you think they're OK and they're toast. You think they're toast and they're OK. 1 year is all I would try to get out of one. Less if it was clogged.

I have a set of forceps (hemostat) that I bought at Radio Shack and I use them for getting pieces of whatever is in a tight space. They have a bend at the tip and are the best thing I have found for this kind of thing.

TX.X-30 fan
07-31-2007, 08:08 AM
I have a set of forceps (hemostat) that I bought at Radio Shack and I use them for getting pieces of whatever is in a tight space. They have a bend at the tip and are the best thing I have found for this kind of thing.

RIGHT. ;) ;)

07-31-2007, 08:26 AM