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gerberpollack 07-19-2008 08:06 PM

Water Pump Issues 98' Maristar
This morning my boat overheated after an hour of skiing. The cause of the problem was the water pump (impeller) disconnecting from the engine. The location of the pump makes it difficult to see if the part broke or if there was another issue.

Can someone tell me how to diagnose the extent of the problem? What is the typical fix for this type of problem? Can I do this on my own or do I need a mechanic?

I purchased the boat 2 months ago and paid for a used boat inspection. Should this problem have been caught by the mechanic?

Thanks for your help.


JimN 07-19-2008 08:23 PM

Which pump- raw water or circulating?

You didn't show which engine you have- TBI or LT-1?

"The cause of the problem was the water pump (impeller) disconnecting from the engine."

Can you be more specific about this? How did it disconnect?

gerberpollack 07-19-2008 08:50 PM

More Information

I'm referring to the pump next to the alternator at the rear end of the engine. I believe it's the main cooling pump and the hose pulls water from a hole next to the gas tank. The engine is the corvette LT 1.

The two hoses are connected to the brass (metal) housing, but the housing is not connected to the male connection (looks like it spins the pump). It doesn't look like the housing cracked away from the spinner. However, there were ball bearings on the floor of the engine compartment.

Thanks for the advice.


JimN 07-19-2008 09:41 PM

If they had removed the belt, they would have found that the bearings were going bad. However, that's not a common thing to check unless it was making noise. If it went this soon after buying it, I would be surprised if it was quiet. How stable was the temperature gauge since you bought it? Did it ever overheat before? The bearings went away and while it may be repairable, it may be better to just replace it.

Don't run it until the pump is replaced. That's your raw water pump, by the way. You have aluminum heads and they really don't do well with overheating. Also, if you ever need to replace the circulating pump, you can't just go to an auto parts store and say "I need a water pump for a Chevy 350". Yours is Corvette-specific and cools the heads before the rest of the engine. It's called reverse cooling and it's not the same part. The raw water pump you need is slightly different, too and it's in the link below.

I don't know if you'll be doing the work on your motor but if you will and know about this motor, great but if you don't, you may want to get a manual. The side panels come out and this makes working on the motor a lot easier. The sun pad has a pin that hold it onto the ram and it's a waste of time to try working on anything under it with the deck in place, but you DO NOT want to just let the deck flop back because it'll damage the gelcoat, fiberglass and the deck. I used a piece of rope with a snap hook on one end and a loop that would go over the ball on the pylon. I would let the deck open about 30 degrees past vertical and it makes life a lot easier.

The alternator needs to be loosened, then rotated down so the belt and bracket can be removed. There's a small machine screws (Allen head) on the bottom of the pump that will need to be removed, then three or four larger machine screws hold the pump onto the crank pulley. Pull the hoses and make sure they go back on the same way they came off- the lower one is the supply and the upper one feeds the thermostat housing. Don't go Ape squat when you torque the bolts on- they all have lock washers, so 25 ft-lb should be fine on the larger ones and snug will work on the lower one..

bigmac 07-19-2008 09:55 PM

Sounds like a fried bearing, which in turn scored and broke the pump shaft.

You're going to need a new pump...I presume you have a 3-bolt mounting flange (where the pump bolts to the crank pulley. Looks like this is the one?

I'd recommend calling them on the phone rather than ordering on the web - SkiDIM is pretty customer oriented and they'll be happy to confirm that that's the right pump for you.


JimN 07-19-2008 09:58 PM

My link wasn't good enough for ya? Ya had to show the picture, didn't ya? Thanks. Thanks a lot!:rant::friday:

bigmac 07-19-2008 10:16 PM


Originally Posted by JimN (Post 519104)
My link wasn't good enough for ya? Ya had to show the picture, didn't ya? Thanks. Thanks a lot!:rant::friday:

LOL. Not a contest, of course, but you added the link and the rest of that info via an edit that you made a minute or two before I posted. You were editing while I was posting.

JimN 07-19-2008 10:28 PM

Yeah, yeah. :D

TMCNo1 07-20-2008 08:20 AM


Originally Posted by JimN (Post 519111)
Yeah, yeah. :D fight!:uglyhammeYa'll make my day!

gerberpollack 07-20-2008 07:16 PM

Quick follow-up question. When the boat was inspected the marina told me i'd need a new impeller. Is this the same part as the one you guys referred to in the previous posts? Also, the marina worked on the alternator a few days before the water pump issue surfaced. Is there any possibility the mechanic could have done something to the pump brackets when he worked on the alternator? The timing of the issue seems a bit fishy.
A few other questions. Do you have a diagram (drawings) of the engine? I’d like to make sure the issue only extends to the water pump. The drawings would be a good way to confirm this hypothesis.

Thanks for your help.


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