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Raw Water Pump Going Bad ?

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The last few trips to the lake I have been noticing more water in the bottom of the boat than normal. Yesterday I noticed there was a little bit of steam that would come out of the exhaust under acceleration but temp gauge didn't read much hotter than normal and was normal when cruising.

This had me thinking the impeller went and today I take the cover off but the impeller looks just fine, all fins intact. I also checked the hoses for obstruction but found none.

I hook up the fake-a-lake and notice that the water leak is coming from the raw water pump and that the boat is not sucking up as much water from the fake-a-lake as normal and very little water is coming out of the exhaust.

Is my water pump dead or is there something else I need to try?

Edited by TTUClint
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What motor?

If it is a merc those plastic water pump housings tend to crack.

If its an Indmar the rear seal on the raw water pump is probably gone, it is about $20 from SkiDIM

Otherwise I would start looking at your packing nut.


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The seal won't stop or prevent water flow. If you really are running above normal temps I'd check the trans cooler for any blockage and replace the impeller anyhow.

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by trans cooler are you referring to the thing just after the pump or where the water enters the boat and runs across the trans. under the rear seat ?

Do I also need to check inside the thermostat housing ? I was trying to do that but couldn't get the hoses off it to take it off.

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Other way, water comes up from the thru hull (under the rear seat) into the V-drive on the starboard side, out on the port side, then it goes to the raw water pump. Keep going upstream and the next thing you hit is the transmission cooler, starboard side of your motor, tube about 3" diameter about 7 inches long with 2 hoses on it that run to the transmission.

Pull the hose off that and stick your finger up and you will probably pull a nice chunk of weeds and other crap out of it.

Again you said your boat ran fine on the water, I would not use once running on a fake a lake to say you are not pulling enough water. The excess water in the bilge is probably coming from that leaky seal or your packing gland.


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Oh the water is no doubt coming from the water pump, so much so that it flings water around as it runs onto the belt.

So even with the crappy seal I definitely have an obstruction somewhere is what you guys are saying ? I will check the trans cooler tomorrow, I tried to get that hose off but it didn't budge easily so I went on.

The boat ran fine yes but the temps would rise at lower speeds and the steam would come out under acceleration.

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I'm not saying you have any sort of obstruction.

If the boat runs hot, it's something to look at.

Water on the belt can come from the GM circ pump too, which is more prone to drip.

Either way, a leak into the bilge from either water pump is not enough to raise engine temps.

Another option would be to run it down to your dealer for a quick check.

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Normally a stop by the dealer would be ideal, but they are so backed up w/ customers new boats and warranty issues right now I wouldn't see my boat for at least a week and have to pay 100/hr to troubleshoot it. We leave for a week long vacation to Arkansas in a week (taking the boat), so I am really trying to get this figured out in a hurry.

We just went ahead and ordered a new pump from skidim so we will be covered there but I sure hope nothing else big might be wrong here.

I appreciate all the help as I am a big time rookie to working on boat engines. Replaced the alternator and wiring a few weeks back and felt pretty damn proud of that.

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Water on the belt can come from the GM circ pump too, which is more prone to drip.

Either way, a leak into the bilge from either water pump is not enough to raise engine temps.

I meant to say that too, definitely see alot more circ pumps go bad than raw water pumps!

To the OP it can be hard to figure out where that drip is coming from since the water gets flung around by the pulleys. There is a weep hole at the bottom of the circ pump (easy to find, the circ pump is the top pully on the drive belt, the hole is at the bottom of it. Usually water will run down and out on the raw water pump bracket.

Good luck,


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Took the water pump off today and took it apart. We ordered a new one from skidim that will be here Monday.

The impeller is still just like new.

The bearings and seals inside the pump totally grenaded.

There were 3 ball bearings inside the bilge and a piece of metal that holds them was near my side compartment, I saw these yesterday but had no idea where they had come from until now.

I also had two pieces of impeller in the trans cooler screen that must have been from a prior impeller.

I also got the thermostat housing off to see that the thermostat was corroded and almost stuck shut so I will be replacing that as well.

Hopefully after getting all of this done I won't see any more problems, I guess if there are then it would have to be the recirculation pump.

Another question, the boat had a heater in it that I removed and just installed a U hose to connect the hoses that ran to the heater. This was 2 years ago I did this but is there any chance that some of my problems i am having now could be because of these hoses running to and from the front of the boat.

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Water is now flowing like a river out the exhaust and is sucking all the water from the fake-a-lake. Clap.gif

Got it all fixed one day before we tow it to Lake Hamilton, Arkansas.

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