50HP Yamaha

[plustax]

Please help..... I have a new 50hp Yamaha and am only getting 2000 rpm at full throttle. Runs max at about 15mph. I'm being told that it's the tach and not the engine. Engine sounds fine, but still .... only 2000 rpm ! It sits on a 20 ft. pontoon boat. Everything brand new.<br /> Help !!!

 

[JB]

Re: 50HP Yamaha

Howdy, Chebytrk.<br /><br />Sounds like you are running on one cylinder.<br /><br />What happens if you pull each spark plug wire with the engine idling? If there is no change you have a dead cylinder. If the engine slows or dies you have a cylinder that is making power.<br /><br />Do you have one or two carbs? If 2, try squirting a bit of fuel mix into each one while you are running under load.<br /><br />Let us know what you find.

 

[nejc]

Re: 50HP Yamaha

Is your Yamaha autolube? If is then check the level of oil,because sometime even on half of resevoar the electronics shootdawn one cilinder.

 

[rickdb1boat]

Re: 50HP Yamaha

chebytrk,<br />I noticed in your other post that you said you were getting 17MPH Top Speed. Thats pretty close to what you will get out of a 50 HP on a Pontoon. I would check and see what Pitch Prop you're running and get Another Tach. I don't believe that you would get anywhere near 17MPH if you were truly only running 2000RPM's or on one clyinder. Plus, you say that the engine sounds fine, which I assume means no "Miss" or anything. I don't know what size prop you are running, but I would say that if you had the correct one, you should hit about 20MPH, with that size motor. Since everything is new, I assume you bought it at a Dealer. The only other thing I would do is take it back to the dealer that sold it to you and have him fix the Tach and check the Pitch of the Prop. Just my thoughts, Rick

 

[Forktail]

Re: 50HP Yamaha

The 50 4-stroke has 4 cylinders and should run between 5-6000 rpm. No oil injeciton, but other faulty sensors could cause it to run powered down. The 50 2-stroke has 3 cylinders and should run 4500-5500 rpm. It could be the oil injection level sensor in this case, or like JB said, it's not firing on all 3. Yamaha may use the economy feature of dropping one cylinder (3 to 2) on their 50. I don't know for sure, but that sensor could be your problem.