Logo
FULL SITE MENU

Mercruiser 43 running hot

sharkin95

sharkin95

Regular Contributor
"I HAVE A 1995 4.3 MERC FWC EN

"I HAVE A 1995 4.3 MERC FWC ENGINE THAT JUST STARTED RUNNING 180-190, SINCE I HAVE HAD THE ENGINE IT NEVER RAN ABOVE 160.HERE ARE THE CIRCUMSTANCES...IT CREEPS UP AT IDLE AND RUNS TO 180-190 UNDER POWER IT STAYS AT 180.THIS IS WHAT I HAVE DONE..REPLACED T-STAT,REPLACED ENGINE WATER PUMP,REPLACED SENSORS IN T-STAT HOUSING.I PULLED THE O/D HOSE AND WATER IS FLOWING,I REMOVED THE MANIFOLD TAP PLUGS AND THE WATER IS WARM,THE RISER'S ARE 3 YEARS OLD THE LEFT IS WARMER THAN THE RIGHT.NOW WHEN I REMOVED THE TAP PLUG ON THE LOWER HOSE ON THE ENGINE WATER PUMP HOUSING THE WATER IS VERY VERY HOT!!!!!! I HAVE A MANIFOLD COMPRESSION GAUGE ON MY DASH IT SHOWS STEADY AT 16 HG I'M STUMPED.}"
 
"THAT SOUNDS LIKE THE USUALL S

"THAT SOUNDS LIKE THE USUALL SUSPECTS.THE RISER THAT GETS HOT TO TOUCH IS THE LEFT ONE, THE RIGHT STAYS WARM.IMPELLAR HASN'T BEEN CHANGED IN 3 YEARS BUT WATER IS FLOWING FROM O/D HOSE HOW MUCH IS SUFFIENT I DON'T KNOW,BUT IT LOOKS LIKE I'M DONE FOR THE SEASON.THANKS"
 
"Jim;
You could do us all a b

"Jim;
You could do us all a big favour first and turn the caps lock off.

Your impeller should pump about 4 GPM at 1000 rpm.
So if you remove the hose at the stat housing, you should fill a plastic bucket in 1/2 minute or so. If not, your impeller is shot.

If you have not had it changed since 1995 it is on borrowed time anyway. Opinions vary, but it should be changed every five years for good measure.

You said your engine is FWC, which means it would have a heat exchanger and a closed block cooling system. Is that right? If not, it is a RWC engine. If it is FWC and your pump is OK, your exchanger may need a cleanout. They get crudded up after a while and suffer from reduced heat exchange.

Rod"
 
"Thanks ROD for the info.I did

"Thanks ROD for the info.I did make a mistake in saying that it is fwc it is not,it is however rwc via saltwater.the o/d impellar was changed about 3 years ago and the right riser was replaced at the same time.The left riser was just cleaned at the same time also.I will do a pump test tommorow it is still on the mooring."
 
Back
Top