160 hp mercruiser overheating mistery

[Stasik]

Folks, I thank you for the future advises!

Almost ready to brake down...

A few month ago I Took my boat (older tri-hull, 21 ft with 160/6 cyl mercruiser) to the ocean for another fishing. On the way back I went crazy and tried to see what it can do. Got maximum speed out and blow the impeller up. Somehow I got back and at home, sure I changed the impeller (all kit with a new cup), then pickup tube between the two halves, then water pump. With muffs on it's working fine. Not overheating for 20-30 min. RPM 1000

Took the boat to the lake to check - overheating after 15-20 min with 1800-2000 RPM

Changed oil and filter - it was old, and run it for 30 min at home with muffs on - it's working fine for 30 min on RPM 1000.
Took it back to the lake - overheating after 25-30 min on RPM over 1800.

Just in case, I changed gas filters and sure, no changes.

I can't think of anything else to be changed.

I just do not want to believe that I could damage the engine.

Any ideas, what else to check what can I do to fix this overheating?

Best wishes to you all!

 

[Bondo]

Re: 160 hp mercruiser overheating mistery

Folks, I thank you for the future advises!

Almost ready to brake down...

A few month ago I Took my boat (older tri-hull, 21 ft with 160/6 cyl mercruiser) to the ocean for another fishing. On the way back I went crazy and tried to see what it can do. Got maximum speed out and blow the impeller up. Somehow I got back and at home, sure I changed the impeller (all kit with a new cup), then pickup tube between the two halves, then water pump. With muffs on it's working fine. Not overheating for 20-30 min. RPM 1000

Took the boat to the lake to check - overheating after 15-20 min with 1800-2000 RPM

Changed oil and filter - it was old, and run it for 30 min at home with muffs on - it's working fine for 30 min on RPM 1000.
Took it back to the lake - overheating after 25-30 min on RPM over 1800.

Just in case, I changed gas filters and sure, no changes.

I can't think of anything else to be changed.

I just do not want to believe that I could damage the engine.

Any ideas, what else to check what can I do to fix this overheating?

Best wishes to you all!

Ayuh,.... Did ya find ALL the pieces of the old impeller,..??

If not, drop the lower unit, 'n back-flush from the t-stat housin', to flush out the pieces ya missed,...

 

[Bt Doctur]

Re: 160 hp mercruiser overheating mistery

Did the new pump kit include the base? If not, the base is warped and sucking in hot exaust.

 

[Stasik]

Re: 160 hp mercruiser overheating mistery

Flushed everything out. Suction is string. Water comes out warm. With low RPMs no overheating.

 

[Stasik]

Re: 160 hp mercruiser overheating mistery

Did the new pump kit include the base? If not, the base is warped and sucking in hot exaust.

If we're talking about impeller kit, then yes. Base, cup, impeller, gaskets and plastic tube...

 

[Bondo]

Re: 160 hp mercruiser overheating mistery

If we're talking about impeller kit, then yes. Base, cup, impeller, gaskets and plastic tube...

Ayuh,.... Then pull the Riser 'n see how plugged up it is,....

Water has to be able to get Out, as well as pumped In,...

 

[Stasik]

Re: 160 hp mercruiser overheating mistery

Ayuh,.... Then pull the Riser 'n see how plugged up it is,....

Water has to be able to get Out, as well as pumped In,...

Good idea. TY. I'll let you know...

 

[Stasik]

Re: 160 hp mercruiser overheating mistery

OK, here I go...even that I'm going to embarrass myself :-0 Riser and manifold are good. Water comes out nicely and warm. Pressure in cylinders 120,120,110,110,120,100. But...what I noticed that I didn't put a thermostat back (old one gone bad and I didn't think that I will need one in California). Now water is pushed up by the impeller to the thermostat housing and most of it going right to the manifold. What I feel is delivering hose getting hot when motor start to overheat. Strange to me, as this is cold water delivering hose and should be cold at all the time? Could the "no thermostat" case cost that overheating? BTW, which would you recommend 140 or 160F? Thank you very much.

 

[Stasik]

Re: 160 hp mercruiser overheating mistery

Riser it is. TYVM! How could I be so sure that 6 month old riser can't be plugged? You're a pro men

 

[Bondo]

Re: 160 hp mercruiser overheating mistery

OK, here I go...even that I'm going to embarrass myself :-0 Riser and manifold are good. Water comes out nicely and warm. Pressure in cylinders 120,120,110,110,120,100. But...what I noticed that I didn't put a thermostat back (old one gone bad and I didn't think that I will need one in California). Now water is pushed up by the impeller to the thermostat housing and most of it going right to the manifold. What I feel is delivering hose getting hot when motor start to overheat. Strange to me, as this is cold water delivering hose and should be cold at all the time? Could the "no thermostat" case cost that overheating? BTW, which would you recommend 140 or 160F? Thank you very much.

Ayuh,.... You can use Either, but you MUST have a T-stat,...

 

[Stasik]

Re: 160 hp mercruiser overheating mistery

ones again, thank you very much and God bless you with a bottle of... with a Ginny inside