Normal running temp for mercruiser 50 v8

"I replaced the impeller and t

"I replaced the impeller and the boat does fine at idle but I was at the lake and was on it pretty hard and the temp went up to about 180-190 at wot, but if I slowed back down and just idle it went back down.Is that normal and can anyone tell me what normal temp should be at wot.Thanks"

What kind of engine?
what typ

What kind of engine?
what type of cooling?
What degree thermostat?

"sorry about that,Its a 5.0v8

"sorry about that,Its a 5.0v8 mercruiser,and it use lake water to cool it,and I dont know what temp thermostat it has"

what year engine? Probably a

what year engine? Probably a 140-143 F. T'stat.

Overheating at higher speeds i

Overheating at higher speeds is generally caused by restrictive water passages in the exhaust manifolds and risers/elbows.

are they just tubes or are the

are they just tubes or are there some kind of things that open and close that let water in.Thanks

"No, the passages are cast int

"No, the passages are cast into the risers and elbows. They will need to be cleaned by a radiator shop or replaced."

Is there a way I can clean the

Is there a way I can clean them myself or to see if they need replacing.Thanks

"Yes; remove any brass and sub

"Yes; remove any brass and submerge (cast iron only) them into a plastic tub full of muriatc (pool) acid for 90 minutes - DANGER, SEVERE BURNS. Wear a face shield, long heavy duty rubber gloves and rubber rain hat and coat. Keep a garden hose w/a trigger spray nozzle and the water on at hand.

The same can be done for a stripped down T'stat hsg. for 30-60 minutes or until clean.

Remove and rinse well w/clean water. Rod the passages out w/a stiff rod to break loose any scale or deposits. Wire brush the passages where a rod won't fit; repeat the soak procedure for 30 minutes if needed. Rinse well, dry and repaint w/engine enamel."