2000 Mercury 25hp 2 stroke telltale/thermostat question?

sutor623

Rear Admiral
Joined
May 23, 2011
Messages
4,089
Hey guys,

Always been a JonnieRude guy. Got a sweet little Mercury 25/20 Jet in great shape. When the engine is running it takes about 30 seconds to start flowing out of the telltale. The flow is strong and increases with RPMs. But, the water is very warm, nearly hot coming out of the telltale. The head on the engine is right at the temp it should be at, 120-140 with the temp gun. Serial number is OT125696, and the motor DOES have a thermostat.

1.) I am assuming that the telltale is AFTER the thermostat on this engine?

2.) So when the stat is closed, very little water flow. When the stat is open, the water has actually already flowed through the block/head before it comes out of the telltale and this is why it is warm water?

I am used to the Erude motors where the pisser is BEFORE the stat, so it flows cool, continuously. Thanks guys!!
 

flyingscott

Fleet Admiral
Joined
Apr 8, 2014
Messages
8,154
The tell-tale comes right off of the thermostat housing. Yes the tell-tale water will be hot. Yes the thermostat controls the flow to tell-tale. If you follow the tell-tale hose up to the block you will see the thermostat housing with the elbow in it. If you just got it change the waterpump now, and every 2 years after on that motor. Only run 50-1 fuel mix and it will be a good motor for a long time.
 

sutor623

Rear Admiral
Joined
May 23, 2011
Messages
4,089
Thanks Scott. I always do waterpump thermostat and gearcase oil. I am going to cruise up river and do some fishing tomorrow, may put an hour or so on the motor. It's cooling well. If I had gotten my impeller in I would have it in already. Never taken a jet lower unit down so I need to get comfortable with that before I drop it.

Thanks for answering my question!!
 
Top