Engine overheating

Watarski · Posted: Feb 28, 2003 6:52 pm Post subject: Engine overheating

I have a problem that just popped up today. I took the boat out (1999 SAN, GT-40) and when I got in it from putting up the truck, engine temp was climbing. Usually it sits around 140, but I watched it go past 200. I decided to run it to see if it cooled off. It cooled off when I was running it (water being forced in through the block), but as soon as I went back to idle, the temp began to climb again. Yesterday, a family member started it in the driveway for about 10-15 seconds while I was gone. Could starting it with no water running through it for that little amount of time messed something up? Does anyone have a clue as to what could be the problem? Are there rubber impellers on these boats that could've burned up? Any help would be appreciated-

stranded boarder

ohsix · Posted: Feb 28, 2003 6:56 pm Post subject:

id be willing to bet the impellar is burned up. 10-15 seconds with no water is hard on impellars. im not sure how water could have been forced through unless the impellar is completely gone though. if there's any pieces gone off the impellar make sure you find them. most of them should be in the housing.
also dont be a dumby wumby like me last time i changed the impellat i forgot to tighten the hose clamps back down.

Watarski · Posted: Feb 28, 2003 7:02 pm Post subject:

Where is the impeller located? I know where the water pump is, but not familiar with the impeller.

Thanks,
craig

ohsix · Posted: Feb 28, 2003 7:14 pm Post subject:

the impellar should be located on the front of the engine as they are usually belt driven. mine is right under the alternator. it will have at least one hose going to the water pickup in the bottom of the boat. on mine you just loosen the alternator bracket (to loosen the belt) and i just take the whole seawater pump off by detaching the bracket. i find it easier to do it this way rather than putting the pump back together in the boat. the pump housing should have bolts running through. remove these bolts and inside mine there is to metal plates with paper gaskets that seal the pump. you will probably need to replace the impellar and the paper gaskets. when you replace the impellar make sure you angle the paddles the same way the impellar is going to be turning. also i use bearing grease to help get the new impellar in place because it is a pretty tight fit. i wouldnt use oil though because it will make the rubber swell. also remember to clean all gasket and sealing surfaces before you put it back together.
this is a pretty easy and common task. i carry an extra impellar in the boat just incase i ever need one. if the overheating alram goes off on your boat you DO NOT want to run it hot.
hope this helps post if you have anymore questions.

supradoug · Outlaw Joined: 16 Feb 2003 Posts: 131 City: Norman

Impeller is located in the housing on the front of the engine where the fan would be on a car. about 4-5 inches in diamater and has 4 screws holding the front plate on. You can remove the plate and check it. Bet you a few benjamins that is your problem.......

Watarski · Posted: Feb 28, 2003 7:19 pm Post subject:

I guess the water pump that I'm thinking of, under the alternator belt, is actually the impeller. My dad was under the impression the there were no rubber pieces in there, only metal. I guess he is wrong. Or maybe I'm just thinking about the wrong part...

Watarski · Posted: Feb 28, 2003 7:20 pm Post subject:

If it is indeed the impeller, can I pick this up at the local boat/marine shop? Or will I have to order? I appreciate all the quick responses guys-

thanks again,
craig

ohsix · Posted: Feb 28, 2003 7:45 pm Post subject:

you should be able to pick it up at a local marine shop. not sure if any boat shop will have it but im 95% sure any inboard boat shop will have one. the impellar is located in the seawater pump which pumps water from the lake to the engine's water pump. all the info i gave you was based on a mercruiser tige engine your PCM may be different. the parts counter guy should be able to tell you exactly where it is on your motor and step by step how to change it. you only need to be a little mechanically inclined to change it.
most people change theirs every year just because it's cheap insurance.

gaslinger · Newbie Joined: 17 Jan 2003 Posts: 2 City: Chattanooga, TN

A few months back there was a posting with a link to a detailed description of how to change the impeller with pictures. You could search the archives.

Watarski · Posted: Mar 01, 2003 10:07 am Post subject:

I tried searching for the archives and didn't find the link you are talking about. Oh well. Definitely sounsd like the impeller is shot. Thanks again for all the help-

craig

Tim Krasin · Outlaw Joined: 13 Feb 2003 Posts: 104 City: Houston, TX

Ok, definitely sounds like the impeller as others have said. I have a Pro Air with the GT40 - so it's a direct drive boat, thus your engine will be backwards from mine. I just replaced my impeller Friday - not real hard on a direct drive, but a little more challenging accessibility wise with a V-drive. If you're standing on the swim platform on your boat, the impeller housing should be on the left. It's got a 6" or so pulley with three holes in it. You'll actually have to loosen the tension bolt and other mounting bolt (bottom side) for the impeller to get the belt off, then remove the impeller housing. Oh ya, remove the hoses in and out (bottom and top) of the impeller housing. Once the unit is free from the boat it's real easy to swap impellers. The three holes in the pulley make it easy to get to the three housing screws holding the two halves together. Make a mental note at this point as to which way the vanes are oriented on the impeller in the housing. Once apart, wiggle the rubber impeller off it's keyed shaft (don't lose the key). I had to wiggle mine for a while since it didn't move very fast. The new impeller just slides right back on with perhaps a light tap with a hammer. When reinserting the impeller into the other half of the housing, make sure the blades are oriented the same direction as the unit that came out. There you're done - just put it all back together and that's it! Good luck! If you're not up to it, I know my dealer said it'd be $45 for him to do the installation, not including the new impeller.
-Tim