cooling system corrosion in 90 Yamaha

[rustymed]

I have a 1992 90hp Yamaha outboard that several years ago was evaluated when the overheat alarm started coming on at 4200rpm and was found to have corrosion in the cooling system. The temp sensor and thermostat checked out and after having the corrosion cleaned out it ran well for 6 months and started overheating again. It has been run regularly without a problem cruising at 3600rpm and the problem has not progressed. It was always flushed, and now I run "salt away" through it. Any other guys had problems with this engine?Any comments about cleaning out corrosion. It was mentioned that possibly the high lyme content in our water could have contributed. Thanks

 

[Solittle]

Re: cooling system corrosion in 90 Yamaha

Rusty - My guess is that they did not get all of the salt water "crud" out the first time around. This crud is white and cakes up clogging the water passages. It is relatively easy to clean out. I don't know your motor but on OMCs you need to do the heads and the passages around the exhaust cover. Your manual should have a cooling water flow diagram. Many will do the heads only. Your best bet would be to change the impeller and thermostats every two years unless it gets worse.

 

[pine island fred]

Re: cooling system corrosion in 90 Yamaha

rusty. do not remove the exhaust cover unless it is a last resort. at least 12 of the 14 bolts will snap off and overheating will be the least of your worries.

 

[rustymed]

Re: cooling system corrosion in 90 Yamaha

Thanks gentleman,<br />One way or another the place to go back to is getting the cooling system cleaned out again.