Hot Water Flow from a Yamaha 25hp

[CrabGuy62]

Hello folks, I have a 2005 F-25hp yamaha that has what i think is a cooling issue that has been going on for 2yrs now. Motor starts fine and pumps cold water right away after 2-3 mins of idling the pee water gets HOT but the flow of water is still strong. This is when I'm running it with muffs in my driveway. When i use the motor on the open water at 1/4 throttle water temp is fine but when go to full throttle it will sound off my alarm on the motor





















Hello folks, I have a 2005 F-25hp Yamaha that has some cooling issues going on for 2yrs now. When warm up with muffs in my driveway the motor starts right up and pumps water strong and cold but after about 2minutes of idling the water flow is HOT but still pumps strong. When i have the boat on the open water i can run it all day at no more than 1/4 throttle and no problems with water temp from motor but when going into full throttle mode motor alarm will go off. I have changed impeller and thermostat twice in the last 3yrs. Can anybody shed some light on my dark cooling issues? thanks for any advice.

 

[mike_i]

Are you able to run the motor in a tank with something to descale?

Descaling Outboard's Cooling Systems.-

Came across this interesting subject on the matter at : https://www.practical-sailor.com/boat-maintenance/descaling-solutions-for-boats Most of the usual descaling products were tested there, draw your own conclusions... Happy Boating

forums.iboats.com

 

[CrabGuy62]

Are you able to run the motor in a tank with something to descale?

Descaling Outboard's Cooling Systems.-

Came across this interesting subject on the matter at : https://www.practical-sailor.com/boat-maintenance/descaling-solutions-for-boats Most of the usual descaling products were tested there, draw your own conclusions... Happy Boating

forums.iboats.com

Thanks Mike for the link. I'm soaking the passage ways with vinegar now since it's the easiest and less costly way. I use the boat in saltwater 99% of the time. Over the next few days I will soak&flush the motor

 

[Sea Rider]

If that motor was used its entire life in salt water expect all water passages to have built excessive saltsclerosis on the entire powerhead. If flushing with any descaler product must remove the thermo, bolt cup/lid back on to properly flush all water passages specially the entire head using a barrel filled with product. Try Salt Away, the other mentioned descalers are bit aggressive with aluminium compared to.

Happy Boating​

 

[mike_i]

be sure to let us know what happens, hopefully the flush fixes the problem, good luck.