Mercruiser 5.7L strange Temp issue

[abocus1]

Bought an engine that has 135 hours on it. Runs great. Had Alpha I outdrive serviced by trusty mechanic including new impeller. Problem: When transitting through no-wake zone (<5 knots; <=1000 rpm) or in nuetral temp guage will read 190-210 F. Once moving 6+ knots up to 3500 rpm engine temp cools to 140-160 F. Tried playing with the outdrive tilt a bit and may change temp to 180-200 F but not much more than that. Have a closed-loop fresh water system. Am somewhat of a new-bee at this. Any help / advice is appreciated.

 

[Bondo]

Re: Mercruiser 5.7L strange Temp issue

Ayuh,... Either the impeller ain't moving water properly,...
Or the risers are clogged, slowing the water...
Or some hosing was misplaced when the motor was swapped...

Got any pictures, or serial #s,..??

 

[Ancloter]

Re: Mercruiser 5.7L strange Temp issue

Also check lower unit water intakes for cloging or obstruction. Consider doing an engine flush as it's FWC and there may be scale built up on the inside restricting flow.

 

[Don S]

Re: Mercruiser 5.7L strange Temp issue

Am somewhat of a new-bee at this.

That's easy to tell, New-bees almost never give us a clue as to year, and never a serial number. Only thing I can assume is all newbe's think that all 5.7's are the same, and they never read the stickies.

 

[chuter69]

Re: Mercruiser 5.7L strange Temp issue

I'm having the same issue with my 5.7 Mercruiser. I want to make sure the machanic isn't screwing me. What can I expect to have this fixed? Looks/sounds like obstruction or buildup internally. They just had the manifolds off and they looked fine. Paid them now looking deeper in the engine. What can I expect? There are only 210 hours on the engine.

Help?

Advise?

Thoughts??

 

[NHGuy]

Re: Mercruiser 5.7L strange Temp issue

Mine creeps up in temp during idling too. But I keep my idle very low around 625. I just put her in neutral and run her at 1100 or 1400 rpms for a few seconds and she cools right down.
If yours is hot at 1000 rpm's, that's a problem. Also if trim & tilt moves give you a little cooling improvement your bellhousing to transom hose might be kinked or twisted or clogged. That would stink, they are a pain to get to and work on.
But the most important thing is, you paid for it to be serviced. Can he correct the problem? The work didn't turn out as expected.

 

[chuter69]

Re: Mercruiser 5.7L strange Temp issue

I'll know what's going on Monday. They should fix the problem without charging any more... worried they'll say it's something else... guess it could be. we'll see