Merc 140 3.0l Alpha 1 impeller question. Look! pictures!

[chadnort]

Overheated on the lake on Saturday and suspected the impeller and or thermostat. Pulled the lower for the first time and here is what i found. The pump housing appears melted and the impeller looks too big. Should the impeller diameter be 1/4in+ bigger than the diameter of the housing? Also it appears the "impeller key" may have slipped out and let the impeller not turn with the shaft. I dont even know if this is possible, is it? Hose from outdrive to thermostat housing was to hot to touch and temp gauge read 250F. What else could I have damaged? See other post with thermostat photos. Its FUBAR also... Thanks for any reply...

 

[Bifflefan]

Re: Merc 140 3.0l Alpha 1 impeller question. Look! pictures!

The impeller looks correct. Replace the impeller and housing as a kit. Its not to expensive. You can get a lower housing also if needed. I replace the whole thing the first time that way I know what I have to start with.
As for the 250F. The gauge reads the temp of water, if there is no water then the gauge is reading steam or nothing and thus is incorrect. Id guess you had some junk on the inlet and it caused it not to be able to pick-up the needed amount of water to cool it, then when you slowed or stopped it fell off. Also its a good idea to replace the thermostat once they are over heated. Its not mandatory, just a good idea.

 

[chadnort]

Re: Merc 140 3.0l Alpha 1 impeller question. Look! pictures!

Biffle, thanks for the input on the impeller. Previous owner had it replaced right before I bought the boat in April. Thermostat is indeed cooked. Looks original (1985 see other post). Im going to replace the water pump at close of season and hopefully the new thermostat will cool her off for now. My "Tow Karma" is pegged for the year, so I may just splash the boat in the pool and see what else breaks.

 

[averagejoe71]

Re: Merc 140 3.0l Alpha 1 impeller question. Look! pictures!

Do yourself a favor and pull the riser elbow off and inspect it for clogging. I was chasing down an overheating problem and thats what it was. Your impeller looks fine.

 

[Don S]

Re: Merc 140 3.0l Alpha 1 impeller question. Look! pictures!

Your impeller is backwards. They normally flip over to the correct direction, but yours sure didn't. How long was it installed before you actually ran it?
Try putting it in correctly then see if it overheats. You probably need a new impeller (over a year old) and housing (warped) after the overheat.

 

[chadnort]

Re: Merc 140 3.0l Alpha 1 impeller question. Look! pictures!

Don, correct on the reversal on the impeller. I had pulled it out to check out the housing and put it back in for the photo. I ended up using the same impeller (correctly aligned!) and pump housing as the local shop had no replacement housing and noted that the impeller looked good for the rest of the season, which with my work schedule, is like tomorrow. I will note that I dropped the trim tab hex bolt into the lower drive and had to remove the prop to retrieve it. Rookie move, but I did get everything back and the motor ran fine. But your saying impellers are NOT like underwear? You can't just reverse them and they last twice as long?