Lower unit gets hot on the muffs.

[BinLurkin]

Why does one get hot & the other stays cool? The lower unit on the 1979 260 Mercruiser w 350 chev stays cool after 15 minutes running. The lower unit on the 1978 260 Mercurser w 305 chev gets hot. I mean hot. I run them from about idle to 1000 rpm out of gear in neutral. The only reason I noticed it was because when I unhooked the muffs some water dripped on the lower unit & hissed at me & steam came off as the water evaporated. Thanks.

 

[Bondo]

Re: Lower unit gets hot on the muffs.

Is there any Oil in the Hot 1 ?????<br /><br />Shouldn't be Hot......

 

[WillyBWright]

Re: Lower unit gets hot on the muffs.

Get a sample of gearlube from them and compare. If there's any difference, one has a drive problem. I'm sure you can guess which one. It could also be a weak water pump. Generally on twins, it's wise to do mmaintenance in pairs. In other words, if you rebuild one water pump, it'd be a good idea to do both. It could also be a sticky thermostat, or a blockage somewhere. The exhaust is cooled by the cooling water exiting. So your drive heat could be coming from friction due to a bearing problem, or from inadequate cooling water.

 

[BinLurkin]

Re: Lower unit gets hot on the muffs.

Yes, plenty of oil, I just checked that to be sure. It looked new too because it hasn't been out on the water yet since I changed it. Only run on the muffs twice. That motor never seems to heat up to "normal". It barely registers on the temp gauge, just about to the cold side of normal. I put a new thermostat in it a while back too. I don't know how long it has been getting hot on the lower unit. I got the boat two years ago & the guy just put a pump in the lower part before I got it.

 

[Bondo]

Re: Lower unit gets hot on the muffs.

If it's getting as Hot as you say,<br />I have to believe that there are Serious Bearing Issues in that drive.......<br /><br />The temp of the engine is in-line...<br />And, the outdrive recieves little or No cooling effect from the engine cooling water.......<br /><br />I'd pull that drive,+ have it gone thru Now.........