New owner and engine runs hot??? need help

[phoenixhotrods]

I have a 88 sundancer 270 twin 260hp 350's, one engine runs fine, the other runs fine but when under load it heats up, wwhen i back the throttle off it cools down slowly. I never replaced the thermostat in this engine but in the other i did. One riser in the elbow is hot and the other is cool, at the back the water comming out of both sides was hot. When i first started it water only came out of the hot side then after idling water started to come out the other side and it was cold, after 5 min it started to warm up??
Can anyone help me out.

 

[Quint4]

Start with changing the impeller located in the outdrive.

 

[phoenixhotrods]

Just changed the impeller, last night i started it again and both risers were warm, one was warmer than the other. Water was flowing out of both sides, water was warmer on one side as well. Out of the thermostat housing the water was warmer on one side as well.
Maybe i shouild check the thermostat, Its just odd, before all the work was done it ran fine,Maybe some rust pluged a passage somewhere??

 

[Quint4]

It is normal for one elbow to be a bit hotter than the other. Define "heating up", what is the temp gauge getting to? When were the elbows & risers last pulled for inspection and new gaskets? Any chance of stray vanes from a prior impeller clogging a water passage? Is the water hose from the outdrive to the transom kinking?

 

[phoenixhotrods]

So I changed the thermostat and it seemed to be alright and them boom it went to 175, the risers were not hot though so i pulled off the hoses by the thermostat cover to see if there was water flowing and there was allot of water flowing, ???? one riser is a bit warmer and im wondering if i have a bum guage or is one riser plugged?? im going to pull apart one riser, should i start with the hotter one or the cooler one??? oh and one hose off of the thermostat housing is hotter than the other and its on the side where the riser is hotter.

 

[northern]

If you have antifreeze with heat exchangers they could need cleaning. A good rad shop that has worked on them for others before will charge about 100 each.

 

[phoenixhotrods]

I found the problem, it was a pluged elbow at the bottom of one manifold.
Thanks for all of the trouble shooting input.