Motor Issue Need Suggestions

[BrianinMD]

Started up my 25hp Johnson today, problem is it would not idle, it would immediately rev up. I only let it run for about 10 seconds before shutting it off. I had it at the shop for a look over about 2 months ago. They changed the plugs and adjusted the carb, they said it idled great. Not sure what the issue is at this point. Any thoughts?

[sneaker]

Well Brian we don't have much information to work with. What year is the motor, 2 stroke or 4 stroke, carburated or EFI? Have you used the boat in the 60 day period since it was in the shop.? Did it run well then? Is the boat stored outside?

Why did you only run it for 10 sec? Was the motor out of the water? Did you have 'ear muffs on it to provide coolant to the engine and lubricate the water pump impeller? If in the water ,was cooling water visible in the exhaust port?

In 10 secs the motor is still cold and if a 2 stroke  it has little lubrication in the power head. Crankshaft seals are dry, pistons don't seal well and it might not idle at all. Be sure coolant is flowing thru the engine and run it  as slow as it will keep running until it warms up. Then check for proper idling.

[surfer]

How far would it rev up?  2000 RPM not to big a deal to let it run some provided coolant needs are met.   5000 RPM and up, you are wise to quickly shut it down.