Weird overheating (problem 1 of 2)

[Xesvuli420]

Never seen anything like this before, but bet one of you guys has a good idea what it is, here's the dilly o...

If I'm sitting still, and idling, the boat stays at the cool end of the gauge, if I creep forward (as fast as I want to go BEFORE the boat tries to start getting on plain) the temp stays cool for as long as I want.

(however, as a side note, the day I un-winterized it, it was idling with muffs on, and it was overheating)

Once I get on plain, even at the slowest speed required to stay on plain, the boats temp climbs. Even at full speed the boat temp will climb (at the same rate as minimum plain speed). It will go all the way to the hot end of the gauge (the dash before the 240). It may have went further, but I backed of the throttle and allowed it to cool.

Here's the weird part (for my understanding at least)..

No matter what temp it is, If I come to a slow speed, or stop, then WOT, the temp drops all the way back down to the cool end of the gauge for a moment, then starts climbing again. For example...

If I'm running a little hot, say 200, and I slow down for a brief second, then WOT, the boat will start to cool all the way down to say 140. Then it will stay there for about 10 seconds, and begin to start climbing again back to 200 Plus

I can even be right before 240, slow down, and then WOT, and it will cool it back down to around 190 for a second, then go back up again.

I'm not sure that If I left it at WOT it would ever go above the dash mark before 240, BUT i'm not willing to take that chance. In the past season, the boat hardly ever went near 200. HOWEVER, it does seem to slow down the rate of which it is heating once it gets higher. Its almost as if it wants to stay around the 8 or 9 mark. Those are the 2 marks right before 240. Im not sure exactly what temp they represent, but its more than 210.

Anyone have any ideas?

Thank you

 

[Bondo]

Re: Weird overheating (problem 1 of 2)

Anyone have any ideas?

Ayuh,... It's a Wonder the motor runs, at All, if you've been doing this, that Long....
Boy, talk about Abuse....

You need to change the Impeller,... It's Junk... It's moving very little water...
I'd also bet the rubber parts of the exhaust system are Junk as well, from runnin' DRY so much...

 

[Xesvuli420]

Re: Weird overheating (problem 1 of 2)

Ayuh,... It's a Wonder the motor runs, at All, if you've been doing this, that Long....
Boy, talk about Abuse....

You need to change the Impeller,... It's Junk... It's moving very little water...
I'd also bet the rubber parts of the exhaust system are Junk as well, from runnin' DRY so much...

At first I was thinking the impeller as well, but if its the impeller, wouldn't it get to this over time, instead of working perfectly, to not working very well at all from one day to the next?

And as far as abuse, No need to be condescending, the ONLY reason I ran thru these test was because I wasn't so sure it wasn't a gauge problem. I didn't run it for a month like this, a week, or even a day. It was just a few passes in the water

I will check the impeller next time I am around the boat, So thanks for the opinion.

Anyone else?

BTW do boats with open cooling have thermostats? A friends says he had a car that did the exact same thing due to a faulty thermostat. I don't see how it could be a thermostat, I didn't even think open cooling systems would have a thermostat, BUT I don't know everything, that is why I am here =o)

 

[Bondo]

Re: Weird overheating (problem 1 of 2)

wouldn't it get to this over time, instead of working perfectly, to not working very well at all from one day to the next?

In the past season, the boat hardly ever went near 200.

Ayuh,... You said it was overheating LAST season....

A raw water cooled boat motor should be runnin' 140? or 160?, depending on which T-Stat is installed...

Between your 2 Problems, it shouldn't run much over a Grand or so,...
Mostly because of a Lack of Maintanance...

 

[cooter2506]

Re: Weird overheating (problem 1 of 2)

WHEN was the last time the impeller was changed? They are a yearly maintenence Item. Very important part if it fails it can lead to BIG problems.

 

[Don S]

Re: Weird overheating (problem 1 of 2)

Check & replace the impeller. It's the first thing you check on any overheat problem on a boat. There are about a million ways to kill one. Including plastic bags over the pickups on the drive.

Check your PMs. (Private Messages)

 

[Xesvuli420]

Re: Weird overheating (problem 1 of 2)

WHEN was the last time the impeller was changed? They are a yearly maintenence Item. Very important part if it fails it can lead to BIG problems.

Thank you, I will look there before anywhere else. However I was told that last season when I bought the boat, it had just been changed. But who knows, they were trying to sell it =o)

Check & replace the impeller. It's the first thing you check on any overheat problem on a boat. There are about a million ways to kill one. Including plastic bags over the pickups on the drive.

Check your PMs. (Private Messages)

thank you, and check yours as well

 

[TRONMAN2000]

Re: Weird overheating (problem 1 of 2)

You could be sucking air into the system at the outdrive when you get on plane and the leg is exposed to air. When you slow down, the leg is completely submerged again and it begins to cool off. No more air. Could be a bad hose connection where the water pickup hose goes through the transom. Just a thought.

 

[Xesvuli420]

Re: Weird overheating (problem 1 of 2)

You could be sucking air into the system at the outdrive when you get on plane and the leg is exposed to air. When you slow down, the leg is completely submerged again and it begins to cool off. No more air. Could be a bad hose connection where the water pickup hose goes through the transom. Just a thought.

THANK YOU, see this makes more sense to me... Same as it over heating when it was on the trailer with the muffs.

to me logically, if the impeller could suck up enough water at WOT to cool the motor, it should be able to suck up enough to keep it cool at 2000 rpm (slowest speed to maintain plain)

but I will check the impeller as well, because like mentioned before it is something that should be checked yearly

 

[TRONMAN2000]

Re: Weird overheating (problem 1 of 2)

It could be intermittently losing its prime. WOT might be enough rpms to keep the pump primed. Anything in between might let air in. Once again, just thinking out loud.

 

[Xesvuli420]

Re: Weird overheating (problem 1 of 2)

It could be intermittently losing its prime. WOT might be enough rpms to keep the pump primed. Anything in between might let air in. Once again, just thinking out loud.

Only problem with this idea is that while yes WOT will cool the motor back down, it only cools for a minute, then it starts heating up again. Thats why I am so confused.

BTW thinking out loud is exactly what I need, so please, keep doing it!

Thanks again

 

[TRONMAN2000]

Re: Weird overheating (problem 1 of 2)

I'm not familiar with OMC drives, but I know that Volvo drives have a water intake hose connection at the transom that can corrode and become a weak point that will introduce air into the cooling system when on plane.

 

[Viking...]

Re: Weird overheating (problem 1 of 2)

I had a similar issue last season.

It turned out to be a worn tube that runs vertically within the outdrive, letting in air when on plane, causing the temp gauge to climb.
This is also similar to the issue already mentioned about the fitting that corrodes.

To find the problem, I connected a garden hose and ran water backwards through the outdrive. A bit of duct tape to hold the muffs tight and create a bit of back pressure, plus a well placed finger where the water was also coming out, was all that was needed to show me the leak.

For what it's worth, that was my experience.
Hope it helps, good luck!

 

[Xesvuli420]

Re: Weird overheating (problem 1 of 2)

I had a similar issue last season.

It turned out to be a worn tube that runs vertically within the outdrive, letting in air when on plane, causing the temp gauge to climb.
This is also similar to the issue already mentioned about the fitting that corrodes.

To find the problem, I connected a garden hose and ran water backwards through the outdrive. A bit of duct tape to hold the muffs tight and create a bit of back pressure, plus a well placed finger where the water was also coming out, was all that was needed to show me the leak.

For what it's worth, that was my experience.
Hope it helps, good luck!

will check that next... Thank you!

Ok as of now I pulled off the impeller, and here are some pics for you guys. This may be a problem as well, but I think viking and tron are also on to something.

To me this looks all kinds of messed up... but this is the first time ive ever seen an impeller.

what do you guys think?

 

[Xesvuli420]

Re: Weird overheating (problem 1 of 2)

btw, yes I know I need a new gasket lol

 

[rockyman]

Re: Weird overheating (problem 1 of 2)

it sounds like you already know whats wrong and dont want listen to the pros, so you should just run it til it stops running then go buy another motor.these guys have been tikering with motors for years so save yourself so time and money and take their advice,if not stop wasting their time.just my two cents worth.

 

[Dan F.]

Re: Weird overheating (problem 1 of 2)

All of your impellor vanes are supposed to be facing in the same direction. Yours are not which means it's toast. Judging by the last pic it looks as though your housing is warped as well. Replace that stuff and that should take care of your overheating problem. If your engine is raw water cooled,I would go ahead and replace the thermostat as well. Good luck man.

 

[Xesvuli420]

Re: Weird overheating (problem 1 of 2)

it sounds like you already know whats wrong and dont want listen to the pros, so you should just run it til it stops running then go buy another motor.these guys have been tikering with motors for years so save yourself so time and money and take their advice,if not stop wasting their time.just my two cents worth.

why do people on here just want to run their mouths? dude why did you even feel the need to open your big fat mouth? I haven't ignored anyone's ideas on here, hell I just said that 2 of the last guys to post sounded dead on!

HOW AM I NOT TAKING THEIR ADVICE?

a few said check the impeller, well that's what Ive done, i even uploaded pictures to see what they thought. It looks bad to me, the housing and all.

a few said check the connections for leaking air, that's what im doing now!

Where do you get off acting like im ignoring anyone's advice? This place use to be a good place to come get help... Seems like now you get more snide remarks, and criticism from people like you.

If all you have is a smart ***** remarks to add to the topic, please stay off my thread. Your not needed, wanted, or anything else!

 

[Xesvuli420]

Re: Weird overheating (problem 1 of 2)

All of your impellor vanes are supposed to be facing in the same direction. Yours are not which means it's toast. Judging by the last pic it looks as though your housing is warped as well. Replace that stuff and that should take care of your overheating problem. If your engine is raw water cooled,I would go ahead and replace the thermostat as well. Good luck man.

Thank you! I was kinda thinking the same. The housing looks all egg shaped and stuff. I assumed that it was supposed to be round (common sense right) but as I said before I have never seen an impeller, and that's why im here.

either way thanks man!