View Full Version : What is the difference water pump and impeller

07-17-2006, 01:00 PM
I went in shallow water and sucked up some silt... The motor over heats.... I searched to find out if I need to replace the water pump... All I can find is info on the impeller.... So I guess I am dumb... But what is the difference in the water pump and the impeller? And if there is a diffenece... Where is the impeller located? Thanks for any help you guys can give me.... Also where is a good cheap place to buy the parts.

07-17-2006, 01:08 PM
what boat do you have... DD or V drive? make model and year plz!

07-17-2006, 02:26 PM
I have a 99 outback. 310 hp, carb engine.

07-17-2006, 04:02 PM
I would have to reccomend skidim.com . most will agree they know there shiZ... and I found their prices good. Just call and ask if you are not sure what part you need. Impellers are like $30

Not sure I have the background to disseminate "waterpump from impeller" I just know what one looks like!

but I would look at your impeller first. its on the front side of your motor. which is the stern (back) of your boat if you have a V drive... not sure on a DD?

07-17-2006, 06:35 PM
The impeller is a small rotating pump mounted to the front of the crankshaft pulley (that is the big one at the bottom). Its job is to pull raw water (lake water) up from beneath the boat and push it into the engine, or more specifically the water pump. The water pump, which is quite large, is mounted directly to the front of the engine and is driven by its own pulley, just above the crank pulley. The job of the water pump is to circulate the raw water throughout the engine to keep it cool. The water pump itself is probably not strong enough to do both jobs, but more importantly the water may cycle through the water pump more than once, with the help of the thermostatic valve (thermostat) depending on the temperature of the engine and such. The impeller "pump" contains a small vaned rubbery impeller inside (behind the small cover plate with the three small screws) and is subject to damage from debris in the water, and over time it gets weak and brittle. The water pump also has an "impeller" but it is a different design and made of metal, so it is more durable. If you sucked up trash and overheated the boat, you probably damaged the rubbery impeller, and now it will not pull water from the lake, so no water is circulating through your engine. This is very bad. If you run it for too long like this, the motor will get so hot the pistons will literally seize inside the engine. The impellers are pretty cheap, about 30 bucks, and not hard to replace, except getting the old one out can be a little difficult, although it is okay to destroy it in the process, since you are replacing it. Some boating supply places or marinas carry them on the shelf, if you know the model number, and most certainly most ski boat dealers carry them. I bought my last one at the Mastercraft dealership because I drive by it on the way home, and the Moomba dealership is an hour away. They looked at me kind of funny, but we run Indmar engines, just like they do. It really should be change once a year regardless of it condition, it is cheap insurance. Your situation is also a perfect example of why many people (including myself) carry a spare impeller on the boat at all times. I hope this helps and good luck on the repairs!

07-17-2006, 06:55 PM
Yes it does.... This is the first time to own a ski boat... So I didn't know about the impeller... Now I do... So I WILL keep an extra one on hand.... I am thinking of just going ahead and replace the water pump and thermostat... Since it has over 300 hours on it... And has a little build up inside the water pump...

I did run it for a little while... But I don't think I ran it long enough to hurt anything... The oil is still clear... I am going to change the oil also... And it starts up and runs... Then engine never did smoke.... And it didn't go to 250... Well the temp gauge didn't.... I would let it cool off while I had something to drink... Then drive it till it would get hot... Then do it all over again untill I made it home... But I did melt the plastic a little where the exhaust comes out... And lost the flapper valves... But all in all in could have been a lot worse.

Thank all of you for your replys...It has helped alot.