high speed overheat in 1993 Sea Ray Laguna WAC twin 5.7 Mercruiser shaft drive

[1993lagunawac]

Hello all,

I am new to this forum and new to larger boats and specifically shaft drive. I am having issues with a high speed overheat on the starboard engine. I have twin 5.7 Mercruisers with about 100 hours since rebuild. The boat is 29 ft and is shaft drive.

I had a small issue with a sand bar and an unclearly marked channel not too long ago, and I am wondering if I may have sucked something into the cooling system.

My question is, does anyone have details instructions or best practices or methods to back flush the cooling system so I can make sure to clear all debris if any before I move into more costly repairs. I have seen another post about a high speed overheat, but what I am looking for is help, direction, SOP and lessons learned for back flushing the cooling system, so I thought starting a new post would be better than hijacking someone else?s post.

Thank you for your help,

Brian

 

[Lyle29464]

Re: high speed overheat in 1993 Sea Ray Laguna WAC twin 5.7 Mercruiser shaft drive

If you have a closed system remove the sea water input hose at the exchanger. Get hardware to reduce that hose down to a fitting that will screw onto you garden hose. If you have a open system hook garden hose to the seawater source at the engine.

forgot if its full of sand you will need to tap on the hoses near the coolers.

 

[oops!]

Re: high speed overheat in 1993 Sea Ray Laguna WAC twin 5.7 Mercruiser shaft drive

have you checked the impeller on the water pump?....or checked the sea strainer?

the above is correct on the flush

 

[1993lagunawac]

Re: high speed overheat in 1993 Sea Ray Laguna WAC twin 5.7 Mercruiser shaft drive

@ Lyle29464 : thank you very much for the instructions. I will give it a shot.

@ opps! : I know it will be due for a water pump rebuild soon, before I did it early I wanted to try to flush it to see if it was necessary to rebuild it early. Thank you for the verification of the back washes directions.

Thanks again for the help.

B