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Overheating??


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Ok, got the boat out all weekend had a blast. Gonna be the best summer for sure!!! Now, I just got done putting a full system in the boat which draws TONS of current. So at times to keep the system going I start the boat and let it run at idle at the sandbar. After an hour or so of sitting idle(maybe more), I notice the boat temp gets a little hot around 225 may even get higher if I let it. So I cut it back off, but if I go drive it the temp drops back down to 175 after a couple of minutes.(maybe even 30 seconds)

The impellor was just replaced, I don't know if it's ever had this problem before because I wouldn't sit for long time frames idle.

I'm ok with it I guess, but if it should be able to run hours on end without overheating I would perfer it to.

Plus what temp is super damaging to the motor? 250 is blowing head gaskets?

Thanks to everyone!!

BTW, pics coming soon on full system install and dash update. :thumbup:

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How close to the bottom of the boat is the sandbar? You might be sucking up a lot of sand or starving the cooling system. You could consider speeding up the raw water pump if you intend on frequiently operating like that, the raw water pump is pretty linear in supply, so at idle you are getting about 6-8 gpm compared to 30 gpm at 3000 rpm. That would be fresh water, the system does recirculate water constantly as the plumbing is set up that way.

Edited by Woodski
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How close to the bottom of the boat is the sandbar? You might be sucking up a lot of sand or starving the cooling system. You could consider speeding up the raw water pump if you intend on frequiently operating like that, the raw water pump is pretty linear in supply, so at idle you are getting about 6-8 gpm compared to 30 gpm at 3000 rpm. That would be fresh water, the system does recirculate water constantly as the plumbing is set up that way.

Water is probably 39" deep.

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91, I would check to make sure you don't have blockage in your oil cooler from a previous impeller that deteriorated.

Try bumping up your idel and see if it makes a difference. I know sometimes on a hot day I have to idle up a hair to keep the temp below 190 or so but mine never climbs above 200. Seems like somthing may be blocking your flow. Check the strainer to make sure you didn't suck up any gunk. Flashlight and a hook to to fish out any crap...climb under the boat while it's on the trailer and giver her a look see.

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How close to the bottom of the boat is the sandbar? You might be sucking up a lot of sand or starving the cooling system. You could consider speeding up the raw water pump if you intend on frequiently operating like that, the raw water pump is pretty linear in supply, so at idle you are getting about 6-8 gpm compared to 30 gpm at 3000 rpm. That would be fresh water, the system does recirculate water constantly as the plumbing is set up that way.

Undersized pulley on the raw water pump. Do that.

My boat will occasionally set off the temp alarm after a hard pull while idling back to the dock. Bump the throttle, even in neutral, and it goes away.

Great idea Woodski.

Edit: Also, add more batteries and charge them overnight.

Edited by jk13
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91 Sunsetter, do you let the engine idle for up to, or over an hour? Yikes that's a LONG time. Do you have a two battery set-up? That may be a better investment, then idling that long.

Steve B.

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Also consider upgrading to a higher amp output alternator to charge those batteries faster. I recently replaced mine with a 200 amp alternator. It should cut down on charging time, possible cutting the idle time in half. Consider 2 or three batteries. The real question here, how much current are you pulling off the battery while running the stereo on the sand bar? With gas near 4 bucks a gallon, the engine is a very exspensive battery charger at idle.

My raw water pump runs directlly of the crank. Its not possible to undersize the pulley, there isnt one.

Edited by WakesetterE
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Also consider upgrading to a higher amp output alternator to charge those batteries faster. I recently replaced mine with a 200 amp alternator. It should cut down on charging time, possible cutting the idle time in half. Consider 2 or three batteries. The real question here, how much current are you pulling off the battery while running the stereo on the sand bar? With gas near 4 bucks a gallon, the engine is a very exspensive battery charger at idle.

My raw water pump runs directlly of the crank. Its not possible to undersize the pulley, there isnt one.

Still looking forward to your review of your mod? Have you had the chance to use it yet?

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Still looking forward to your review of your mod? Have you had the chance to use it yet?

This weekend, three days on the water. Muffler due in today via UPS, so I'll be back in the game. Cant wait! Full report when back on tuesday!

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91 Sunsetter, do you let the engine idle for up to, or over an hour? Yikes that's a LONG time. Do you have a two battery set-up? That may be a better investment, then idling that long.

Steve B.

I have 2 batteries currently, 1 NEW deep cycle dedicated to the system and 1 NEW cranking battery dedicated to the engine. When running it draws on both, but otherwise just from the system battery.

As far as idle time, I don't really pay that much attention to time when I'm on the lake. So I'm guessing around an hour or so. We get it when we are out there. :cheers:

And as far as gas goes, I think the boat is amazing on gas! I think we were out from 11 am till 8 pm Sunday and only used maybe half a tank!! Not bad at all when your spliting it.

Sounds like from the replies that most of you guys are suggesting alternatives instead of fixes. Which sounds like it could be normal for it to do that??

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martinarcher

I've idled the boat in the driveway on the hose for probably 15 minutes and never seen temps over 160. I just can't imagine idling the boat for an hour. I would certainly think temps over 200 are abnormal though. I would pull the impeller hose from the raw water pump to the tranny cooler and make sure you don;t have blockage. Also, check the hull scoop for blockage as others mentioned.

One thing to consider would be taking it for a quick spin to charge batteries instead.

An alternator doesn't produce full current or anywhere near it at idle. Also, are you running the stereo while the boat is idling? I would bet if your running the stereo hard while idling you'd be lucky to charge much at all. For a good charge, put it on charge at night before hitting the lake, then if it needs it, shut off the stereo and take the boat for a spin....heck ski a little and then come back to the sandbar.

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I've idled the boat in the driveway on the hose for probably 15 minutes and never seen temps over 160. I just can't imagine idling the boat for an hour. I would certainly think temps over 200 are abnormal though. I would pull the impeller hose from the raw water pump to the tranny cooler and make sure you don;t have blockage. Also, check the hull scoop for blockage as others mentioned.

One thing to consider would be taking it for a quick spin to charge batteries instead.

An alternator doesn't produce full current or anywhere near it at idle. Also, are you running the stereo while the boat is idling? I would bet if your running the stereo hard while idling you'd be lucky to charge much at all. For a good charge, put it on charge at night before hitting the lake, then if it needs it, shut off the stereo and take the boat for a spin....heck ski a little and then come back to the sandbar.

Thanks, I will try to take it apart and look for blockages. I was thinking of adding another battery, but was told I would probably only gain about half an hour or so in play time. Seems costly for half an hour, not to mention take up even more room.

I bet I could somehow put a voltage display on the system battery to keep track of when I need to run the boat and for how long.

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Consider pulling and checking the thermostat, it may have failed partially open restricting flow at idle. Mine never runs hot at idle, but I have never idled over 15 minutes.

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Yeah, I can idle in the driveway or out on the lake all day long and stay right around 140-145. 225 is getting dangerously high IMO especially for any extanded period, but you say it comes back to 175...do you have a 180 thermostat? I can beat on my boat like a rented mule and not get it to go over 165, I would check out all the above suggestions asap.

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martinarcher

Thanks, I will try to take it apart and look for blockages. I was thinking of adding another battery, but was told I would probably only gain about half an hour or so in play time. Seems costly for half an hour, not to mention take up even more room.

I bet I could somehow put a voltage display on the system battery to keep track of when I need to run the boat and for how long.

Good idea.

About the extra battery, an Interstate SRM-29 should give you quite a bit more run time. Like hours more. Check out this thread.

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Definitely sounds like some kind of overheating issue. Get that straightened out first, and I don't think you'll have to mess with battery's, since you have two good ones now. I changed to a 160 thermostat, and the engine like's that.

Let us know what you find,

Steve B.

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Being a 91 you've def got a Mercruiser, no?

You've defenitely got an overheating problem. We can idle around the lake all day and not go above 160. I vote trans cooler blockage or bad impeller installation. tighten it (Jabsco pump on a Mercruiser) too tight and it tears up the impeller or keeps it from spinning causing the shaft to separate from the vanes.

Or it's the thermostat.

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Being a 91 you've def got a Mercruiser, no?

You've defenitely got an overheating problem. We can idle around the lake all day and not go above 160. I vote trans cooler blockage or bad impeller installation. tighten it (Jabsco pump on a Mercruiser) too tight and it tears up the impeller or keeps it from spinning causing the shaft to separate from the vanes.

Or it's the thermostat.

When you check the impellar check the backing plate on the water pump housing also. Its plastic and can wear out, grooves etc.

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I agree with everyone, check the oil and cooling system. You should not be overheating like that no matter how long you idle, have you tried idling with a fake-a-lake hooked up to see if you can duplicate the problem. You don't have to run it long just to notice the temp starting to rise?

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