Motor overheating when trolling

[fishin2]

I have an I/O and when boat is idling along when trolling my motor is overheating. Replaced the thermostat and thought the water pump was bad, but when I pull my poles in and just idle her up a little, it cools right down, any suggestions. Any help is appreciated, Mike

[Fish Tales]

Check the impeller in the seawater pump.

[wakina]

Check the impeller in the seawater pump.

I believe Fish Tales has almost certainly found your problem!

In case you have never had to change one before here is where they are located. If it is an Alpha 1 Generation 1 or 2 the seawater pump is in the lower unit! If it is a Bravo drive of any series 1, 2 or 3 the sea water pump is located on the bottom of the engine most often on the starboard side at the front! I have no experience with the OMC drives so cannot give any advise on them!

[sherman51]

do you have the closed water system with the raw water pump on the front of your motor, or do you have the outdrive pump?? if you have the closed water system it could just be alittle low on antifreeze. or you could have a bad impeller.

we was working on my motor one time on my mercruiser and we shut the water off to the outdrive. and did some work. then started the motor back up, then noticed we hadnt turned the water back on. so we shut it off and turned the water back on. well everything seemed to be ok, untill i put it on the water. then she overheated, so i replaced the impeller. took her back out and she idled just fine, it was whan we took off down the lake that it overheated. i tried everything i could think of. i replaced the water line on the outdrive run a wire through the pipe that goes through the transome and replaced the water line from the transome to the motor, she still overheated. then i was told to replace the impeller housing and the bottom wear plate. that fixed my problem.

now i talk to this guy on another forum. he has a boat but i dont know much about it except it has the volvo penta outdrive. but year before last he had put a new inpeller in his water pump. but it started overheating at trolling speed. he even took the manifolds off and cleaned them. he just couldnt get it fixed, he took it to another guy to see if he could fix it. he changed the impeller again and that fixed it. i guess he had either damaged the new impeller or just got a bad one to start with. but it had only lasted about 6 weeks.

if you have the outdrive pump i would suggest you change the impeller and upper housing and the wear plate. if you have the raw water pump on the front of your motor i would try just changing the impeller first. then if that didnt fix it i would change the housing. just my opinion.
sherman

[fishin2]

Ordered a complete rebuild kit for the impellar, complete new housing, wear plate, new gaskets,o-rings, and a new water tube, and new impellar. Might as well start with the easy stuff, again, thanks all, hope she trolls good this year cause the jig bite will get most of my milk money !!! Oh yea, I have an open raw water system, impellar in my outdrive type. Mike

[LOWE LIFE]

Its your impeller in the lower unit. Mine did the same thing while its apart you will want to check everything Bellows, Shift cable, bearings, anodes,ect... Better to do it all at once then to have to tear it all apart again.. Takes about a day to do all the work.

[skipper9]

Yeap I agree its the impeller. ..

[fishin2]

Impellar is new, maybe an obstruction ? She cools right off when idled up a touch. Might go the new impellar route again, maybe something not right, thanks, mike

[aerocraftmach2]

Did you get the new housing and all with the impeller? I had one still get hot after putting a new impeller in and once I got the new housing it was fine. Also just last night I put one in and the seal for the copper tube in the upper unit was smashed causing it to leak around it.

[fishin2]

No, did not replace the housing, might not be sealing well, might just go with a total rebuild kit for the impellar. really don't want to resort to an outboard on the rear of the boat. Motor is a Mercruiser, I/O. Thanks all, mike