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WakeWorld Discussion Board » >> Boats, Accessories & Tow Vehicles Archive » Archive through April 21, 2006 » Impeller vs thermostat Overheating! « Previous Next »
By tomek (tomekrys) on Saturday, April 15, 2006 - 6:07 pm:    Edit Post Delete Post
Just put my boat in the water and it started overheating right away. What could this be from? I'm thinking either the impeller or thermostat failing? I hooked up to a fake a lake and there was almost no water coming out the exhaust but this still doesn't tell me what my problem is I don't think. How ofter do impellers fail? I think this one was just replaced. I'm new to boats and especially inboards. Any help would be appreciated.
By tomek (tomekrys) on Saturday, April 15, 2006 - 6:14 pm:    Edit Post Delete Post
Oh yeah its a 1994 Malibu Echelon DD. Is there a filter for the incoming water possibly? I doesn't look like my boat has one.
By Walt (walt) on Saturday, April 15, 2006 - 6:35 pm:    Edit Post Delete Post
I'd check the impeller first.
By Vince Newman (cvnrides) on Saturday, April 15, 2006 - 6:46 pm:    Edit Post Delete Post
Your boat may have a screen in line at the transmission cooler. Follow the hose from the impeller housing toward the pickup point in the hull. There should be metal splice in the line that the transmission lines hook to also. Pull the hose apart and check for trash (sticks, leaves etc.) if that is clear it is most likely the impeller. I have had this problem with two different boats MC and Supra mostly during early season when water has more trash.
By George Aslinger (mobv) on Saturday, April 15, 2006 - 7:11 pm:    Edit Post Delete Post
Very seldom is the thermostat on a boat, it can happen. Most likely is the impeller or a restriction in the intake line. If the impeller is nearly new a restriction in the line could cause the impeller to fail. I had trash plug the oil cooler that caused overheating.
By tdc_worm (tdc_worm) on Saturday, April 15, 2006 - 7:46 pm:    Edit Post Delete Post
fake a lake pushes water through your engine, keeping the engine cool... as soon as your on the water, the impeller has to pull water in to the engine. if you impeller is shot, the fake a lake will fool you into thinking that everything is jiving. once you get on the lake its a whole different story... at the beginning of the season after your boat has sat up all winter, the propeller has dry rotted and disentigrated... get a new one and it will fix your probs...
By Patrick Vega (3205lpv) on Saturday, April 15, 2006 - 10:08 pm:    Edit Post Delete Post
If a thermostat fails it should fail in the open position.
By Big E. (wakesetter101) on Sunday, April 16, 2006 - 7:17 am:    Edit Post Delete Post
I went through the same thing a while back on my boat. In my chase it was just a bad ground wire going to the gauge causing it to read high.
Here is a check list to do.

(1) Check water intake and filter to the impeller.
(2) Check the impeller itself. (DD should be a very easy check)
(3) Check to thermostat.

Are you 100% sure its not the gauge reading wrong? If you want to check the ground wire for the gauge, in the water or with the fakealake. Just run a ground from the battery to the back of the gauge and see if your temp drops.

By tomek (tomekrys) on Sunday, April 16, 2006 - 7:19 am:    Edit Post Delete Post
So like I said I'm new to inboards. But I know that the impeller is housed on a pulley on the bottom driver side of my boat. Do I need to pull this entire unit off the engine or can I simply check if its the impeller another way? Also my boat is currently sitting in the water cause I drove it to a slip to work on it. So I assume that as soon as I disconnect the hoses water from the lake will gush into the boat. Clamp that off with vice grips or something?
By Big E. (wakesetter101) on Sunday, April 16, 2006 - 7:29 am:    Edit Post Delete Post
My boat is a v drive but it should be the same.
Take the four screws out and try not to tear the gasket if you dont have to. Pull out the impeller with 2 screw drivers or maybe needle nose pliers. Check it out.
As far as the water see about placing something to catch it if it is alot. But i dont think it will be.

By Bob (bob) on Sunday, April 16, 2006 - 9:05 am:    Edit Post Delete Post
Im pretty sure the impeller on your boat is above the waterline, therefore the lake will not come gushing in. If its a 94 how long have you owned it? Longer then a year I would say your most likely overdue for an impeller as most are supposed to be changed annually. Real easy on a dd to change.
By Aaron Nielsen (lzyboy) on Sunday, April 16, 2006 - 9:58 am:    Edit Post Delete Post

It's really easy to test your thermostat too... Place t in a pot of water on the stove & heat it up - watch for the thermostat to pop open... If you have a thermo / place it in the watrer to match the opening point...

Like others have said, changing the impeller every season is a good idea / habit to get into... If the old one is in good shape, save as a spair.

Good Luck.


By Greg Filkin (durangopprboy) on Sunday, April 16, 2006 - 12:11 pm:    Edit Post Delete Post
I am going thru the same thing now on my old fishing boat. I replaced impeller still overheated, did the stovetop and stat did not open. I also put the motor together without the stat and ran it. The motor did not overheat. This way I was able to check for blockage other than the stat. The new stat should be here Thursday.

That all being said you can trash an impeller in 30 seconds if water is not hooked up. Never start a boat with out being in the water or a hose hooked up.

By tomek (tomekrys) on Monday, April 17, 2006 - 6:31 pm:    Edit Post Delete Post
So my impeller is probably gone. I should probably turn the engine over to see which way the impeller needs to be mounted before doing anything as I think you could put it on either way correct?
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