Problem:
Engine isn’t running right at low RPMs.
It idles perfectly fine. At high speeds it runs like a top.
For example, running under plane through no-wake zones is difficult. It bogs down.
I can feather it and pump the bulb to get it to speed and it runs like a dream.
What I’ve done:
Replaced fuel filter. It was dirty, but new one didn’t fix issue.
Replaced fuel-water separator: Fuel from inside filter was clean with minimal particles.
Replaced spark plugs: They were black, so seems to be running rich. Problem still exists after running with new plugs.
my first guess would be, your thermostat is getting stuck open. basically not allowing your motor to warm up, causing the motor to run rich and flood the cylinders with fuel, allowing extra fuel to seep into the crankcase. without being at the motor, its a little difficult to pinpoint the issue, but thats a good place to start and relatively common issue.
If I’m posting, its because I’m sitting here at work, dreaming about fishing.
Checked my thermostat…
It was stuck wide open with a good bit of salt buildup around it.
Cleaned everything out really well.
Bought and installed a new thermostat.
Will test on the water later this week and see if this solves the problem. Was a necessary repair regardless, so I’m glad I checked.
Thanks so much, Mechanic, for your advice.
Lastly, it really makes me rethink Yamaha’s hose hookup for flushing saltwater after I get home. I flush it religiously, but the freshwater is obviously not reaching the thermostat. I may just go back to the oldschool approach and use my muffs every time.
The spark plugs I bought were factory gapped to Yamaha recommendations, but I did not double check. I should do that.
Oil change coming up next.
Thanks, again! I owe you a beer at the very least. Remind me sometime.
Buddy of mine had a yamaha f250… bad thermostat added what seemed to be an extra 1.5qt of gas in the oil,mainly from slow trolling in the winter…oil got so thin lost oil pressure and spun a bearing. motor was shot
Moral
Yamaha puts the flush adapter on the motor for situations that prevent you from running the motor, such as a boat that stays in the water.
it is strongly recommended that you use a flush adapter on the lower unit and run the engine for 5 minutes with fresh water.
Moral
Yamaha puts the flush adapter on the motor for situations that prevent you from running the motor, such as a boat that stays in the water.
it is strongly recommended that you use a flush adapter on the lower unit and run the engine for 5 minutes with fresh water.
Moral
Yamaha puts the flush adapter on the motor for situations that prevent you from running the motor, such as a boat that stays in the water.
it is strongly recommended that you use a flush adapter on the lower unit and run the engine for 5 minutes with fresh water.
Moral
Yamaha puts the flush adapter on the motor for situations that prevent you from running the motor, such as a boat that stays in the water.
it is strongly recommended that you use a flush adapter on the lower unit and run the engine for 5 minutes with fresh water.
Moral
Yamaha puts the flush adapter on the motor for situations that prevent you from running the motor, such as a boat that stays in the water.
it is strongly recommended that you use a flush adapter on the lower unit and run the engine for 5 minutes with fresh water.
The poppet valve, if malfunctioning, will not allow the water pressure to build up on the muffs. I pulled the foot off twice to replace the impeller and checked it again because of overheating on the muffs(150 4S). Read about poppet valves…great design but just something else to fail. The 4 stroke is easy to get to…not so much on older motors:
