270 GM running hot

[capndan63]

Hello I am new to this forum and hope to find help with my engine. I have twin inboard 350s with closed cooling in my Luhrs, one is running hot at high rpms 3100 and higher. All the usual suspects (risers, impellers, thermostat and hoses) have been checked and or replaced still the problem persists what am I missing?? Thanks, Dan

 

[Don S]

Re: 270 GM running hot

270GM sure doesn't tell us much, could you elaborate. Make, model, year, is this really an inboard or an IO?

 

[capndan63]

Re: 270 GM running hot

Sorry about that! 1999 5.7 Power Source twin screw inboard.

 

[capndan63]

Re: 270 GM running hot

The starboard engine runs at around 160 the port runs at 160 unless I exceed 3100 rpm then it climbs quickly to 190 and higher if I don't cut back the rpm.

 

[Don S]

Re: 270 GM running hot

Did you replace the impellers or just look at them? How old are they? Sounds a lot like an old impeller.

 

[capndan63]

Re: 270 GM running hot

I installed new impellers.

 

[Bondo]

Re: 270 GM running hot

Ayuh,... Have you had the Heat Exchanger Cleaned lately,..??

 

[capndan63]

Re: 270 GM running hot

Yes the heat exchanger has been replaced but it made no difference.

 

[Don S]

Re: 270 GM running hot

Adapt a short piece of clear hose to the inlet side of your raw water pump and run it and see if you have air bubbles, if none, move the hose to the outlet side of the pump and test run again and watch for bubbles.

NOTE: These tests MUST be done with the boat in the water.

 

[Lodgepole]

Re: 270 GM running hot

Not familiar with this set up, but does it have flapper valves in exhaust below the risers? A flapper that broke off and partially blocked the exhaust caused the SAME PROBLEM FOR ME ON A DIFFERENT SET UP FOR ME above 3000.

 

[Don S]

Re: 270 GM running hot

Not familiar with this set up, but does it have flapper valves in exhaust below the risers? A flapper that broke off and partially blocked the exhaust caused the SAME PROBLEM FOR ME ON A DIFFERENT SET UP FOR ME above 3000.

Not only no flappers, but no outdrives to get the flappers stuck in.

 

[capndan63]

Re: 270 GM running hot

Thanks for the help, I will try the clear tubing this weekend and see what happens.

 

[FreeBeeTony]

Re: 270 GM running hot

Is the raw water intake clear?.........No obstructions?