Help! Motor overheating under load

[Intense]

Hey all,

I'm hoping one of you have run into this before.

My motor is overheating....but only when I'm running at speed. Initially, this happened when we were surfing. The engine temp shot up and the motor cut off. So we turned everything off and sat for a couple minutes. Turned the motor back on and everything seemed fine...at idle. Once we were under way again, it shot back up. This time we drained everything and limped home.

Later, I did some testing....

- Motor on and trans in neutral. Motor runs fine, I can run it up to 2500 rpm and hold it.

- Motor in gear and...engine temp will eventually creep up in too hot.

My buddy theorized that trans or v-drive fluids may be low. Admittedly, I have looked at it since winterizing in the fall.

But, does that theory sound solid? Low trans/v-drive fluid causing the motor to work harder. Hence the overheating motor??

Thanks all

~mike

[99response]

Personally I'd start with the impeller and transmission cooler screen for stuff blocking flow.

[Murphy8166]

Discount Inboard Marine - troubleshooting link.

http://www.skidim.com/Faq_TROUBLESHOOT.asp#RWTS

[NorCaliBu]

The smart money bet is that you shredded an impeller. A damaged impeller could deliver enough water to cool a motor at idle but not once you're running. If that's not it check both the transmission cooler for clogs as well as the raw water intake line. It's possible that debris got past your intake thru-hull screen but got caught on the small "grate that leads into the raw water pump.

Good luck. Keep us posted.

[EchelonMike]

My buddy theorized that trans or v-drive fluids may be low. Admittedly, I have looked at it since winterizing in the fall.

But, does that theory sound solid? Low trans/v-drive fluid causing the motor to work harder. Hence the overheating motor??

Thanks all

~mike

I changed my tranny fluid last year and thought I replaced what I took out. Brought some extra fluid out the next lake trip, just in case. Sure enough, backing off the trailer the boat would not move smoothly forward in gear because I was just a bit low on fluid. Topped off dipstick in tranny and all was fine. In other words, if you are low on fluid you will notice it in terms of screwed up forward or reverse motion vs engine overheating.

I agree with others to start with what is simple the check - the impeller. And if the impeller is missing and "teeth", you need to look upstream of the housing to clean out the debris screen. If the impeller looks OK but is more than a few seasons old, change it while you have it all apart - cheap insurance and could still be losing efficiency even if it looks OK. If the impeller is good and the screen clear, I would then move to the thermostat. If it is stuck or sticking, it may pass enough water to keep cool at idle but overheat under power. Also if your boat is on the trailer, look under the boat to make sure the intake in the hull is clear. I have had bits of wood or weeds hung up in my hull fitting before.

Good luck!

-- Mike

[pielet97]

Impeller and I'd bet $.

[Intense]

Just checked the impeller...looks fine. Wasn't able to get the hoses to the water pump off to check the screens...6 years and 1300 hours have practically welded the hoses on!

Talked with my mechanic, he suggested the t-stat. Given I too damn busy right now to test theories, it's jsut going to him.

So, who owes me $$? I take checks :P

[Michigan boarder]

Just checked the impeller...looks fine. Wasn't able to get the hoses to the water pump off to check the screens...6 years and 1300 hours have practically welded the hoses on!

Talked with my mechanic, he suggested the t-stat. Given I too damn busy right now to test theories, it's jsut going to him.

So, who owes me $$? I take checks :P

One way or another, I would get those hoses off. Last year I checked my trans cooler screen, which is past the water pump, and I had some gobs of seaweed in it. Who knows what you've got in there.

Take a heat gun or hair dryer and heat up the end of the hose, get it nice and pliable, and then use a small flat screwdriver to get in between the hose and fitting, and it will eventually pry loose. Or, while it's in the shop, ask your guy to check it, so next time it's easy for you.

It's worth 250 Boarder Bucks. Redeemable anywhere you see a red Echelon with a monkey driving it!

[85 Barefoot]

get a hose puller tool....v drive fluid no bearing on engine temp...agree could be thermo but I also suspect a blockage somewhere.

[wakeboarder3780]

Take a heat gun or hair dryer and heat up the end of the hose, get it nice and pliable, and then use a small flat screwdriver to get in between the hose and fitting, and it will eventually pry loose.

Thats how I got mine off my 89 sunsetter when I had it, minus the heat gun and lots of little inserts with a flat screw driver. Don't be afraid to get a little rough with it. Those hoses are typically pretty tough. I took a screw drive and hammered it in the first 2 or 3 times and just made straight stabs underneath it. After I had a small section loosened up I could scrape around instead of stabbing in. Hopefully that description makes sense.

Sounds like you decided to take it in, but next time that's what i would do.

Edited April 27, 2011 by wakeboarder3780

[Lance B. Johnson]

twisting motion rather than pulling motion helps as well. It is worth covering all your bases on this one....that means new t-stat and cleaning the screens.