Removing Tstat,Rising temp at idle

[crazy charlie]

Ongoing problem. Twin 5.0xl Mercruiser i/os with alphas.Checked and changed just about everything associated with it.Mani,risers,impeller etc.,tstat,t-balls.Started out season fine and temp slowly began to rise again .Only at idle and more recently when coming off plane.Usually a tap up on throttle of 2000 rpms brings down the temp .I pulled the tstat today in attempt to isolate the problem.I am about to order a new tstat housing.Don sent me some good info on the housing and it appears I have the correct one on.I plan on running the boat a day or two w/o the stat and possibly remove the t-balls next.I assume this is safe as long as I dont leave it that way..?? It has been a long process of elimination.Charlie

 

[Don S]

Re: Removing Tstat,Rising temp at idle

With the thermostat out, you are only keeping the engine cooler right at the temp sender for the gauge. The back cylinders of the engine are getting hotter. Reason is, is the water can flow to quickly past the rear cylinders (if at all) and not allow enough time for heat transfer. Without the checkballs, the MORE of the water is going to be diverted to the risers instead of the engine and manifolds. Then it will run even hotter.

 

[crazy charlie]

Re: Removing Tstat,Rising temp at idle

Removing the tballs is a bad idea.Thanks Don.And it sounds like trying to isolate the problem by pulling the stat will result in a lower temp reading while it is actually running warmer .Maybe I will replace the stat instead of pulling it...????