Yamaha 50hp 2-stroke engine problems! please help!

[Stephenboyd]

I have had my boat in Fl for over a year now and have had minimal problems with the engine.I use the boat at least 2x a week. Just a few weeks ago, the engine started hesitating when going 3/4 to full speed. Initially I pumped the gass ball and it was all fixed. Thought I had some air in the gas. But it got worse. Now I can plain off and get going for 30-40 seconds, maybe a minute. And it starts hesitating bad. (throttle, heitate,throttle hesitate, etc) And i must idle down. However i could putt around all day with no problems. Ive tried a seperate gas tank. Replaced the ball. Filled tank w/ non ethenol gas. used sta-bil. Cleaned carbs out twice. checked fuel filter....replaced spark plugs. but not the wires. My old man seems to think it has to do with the carbs. He says they most likely need to be rebuilt?... however they were rebuilt 2 years ago.. was wondering if I can get some input on a few things....

Could it be spark plug wires?
How hard is it to re-build myself?
If I shouldn't how much should I expect to pay to have them re-built?
Is there anything I havnt Checked that could be causing this problem?

Any help is greatly appreciated! I just wanna get out and fish!

 

[kfa4303]

Re: Yamaha 50hp 2-stroke engine problems! please help!

Hi Stephen. I'm not Yamaha expert, but I believe you may have an issue with your fuel pump. The tell-tale symptom was when you said you could manually squeeze the primer bulb and the motor would pick up. I would inspect the fuel pump and fuel lines for any air leaks as well. Many fuel pumps can be rebuilt with a kit, which you can probably get here at iboats as well.

 

[multimech]

Re: Yamaha 50hp 2-stroke engine problems! please help!

Has the boat sat for a lenght of time before use? Your old man might be right if it has. You could have crap blocking up the high speed jets.

Did you do a visual check of the fuel going into the engine? You may have air getting into a leak in a fuel line, quick disconnect.

 

[Stephenboyd]

Re: Yamaha 50hp 2-stroke engine problems! please help!

I have checked visually and the gas goes through the filter easily when the ball is pumped. so the connection I ruled out.
I use the boat 3 times a week on average for the last year.

 

[Bamaman1]

Re: Yamaha 50hp 2-stroke engine problems! please help!

As was said, you may have a fuel pump issue. It's just a rubber membrane that flutters with air coming through the back from the crankcase. 90/10 gas attacks anything rubber.

I suggest you go ahead and buy a new membrane and install it. While you're at it, physically pull the gas filter and visually inspect it for contamination.

If you're still having problems, have the carbs pulled and cleaned. They don't usually need any carb kit if you're careful not to tear any gaskets. It's just a little time and a can of carb. cleaners.

Last time I cleaned my 2 carbs, I pulled them, disassembled and cleaned them, reassembled and put them back on the engine in just over an hour. And I'm no mechanic.

 

[renegade15]

Re: Yamaha 50hp 2-stroke engine problems! please help!

I cleaned my carbs twice, with carb cleaner and compressed air, AND ran a single strand wire through every passage I could. Still had the same symptom you describe. I finally had my mechanic soak them in a ultrasonic cleaner for me, put them back in, did link-n-sync, and the thing runs better than it ever has. Not sure where in FL you are, but if you are near St Pete I'd give Stellar marine a call and talk to Joe, or in Tampa Jack's Interbay is great. If you do tackle it yourself, which would be a very good thing to know how to do, be careful that you use a proper sized screw driver to remove the jets or they can be damaged easily.

 

[James R]

Re: Yamaha 50hp 2-stroke engine problems! please help!

Dont ever put "carb cleaner" near your carbs. Carb cleaner can destroy carb parts. I soak all stripped carbs in Gunk Carb and Parts cleaner for a half hour or more. Run a fine wire through tiny drillings. May need to break up any stubborn deposits. A further soak and rinse with fresh water. Blow out with compressed air. Put in my Ultra sonic tank at 40 Degrees for thirty minutes, rinse and blow out with compressed air. Check with penlite and reassemble with new kits.
If they are not clean after that then I go back in.
What I am trying to say is do a proper job!

 

[Capt Ken]

Re: Yamaha 50hp 2-stroke engine problems! please help!

Do not immerse outboard carbs in any chemical dip. There is bushings that can become damaged from the caustic solution. Seen this happen more than once that led to replacement of the carb.

 

[James R]

Re: Yamaha 50hp 2-stroke engine problems! please help!

You need not be concerned about soaking in Gunk Carb and parts cleaner. It will attack some rubber parts and gaskets but will not harm plastics and metals. I have been using this product for years on all brands old and late models without issue.

 

[squealer]

Re: Yamaha 50hp 2-stroke engine problems! please help!

Hi Stephen. I'm not Yamaha expert, but I believe you may have an issue with your fuel pump. The tell-tale symptom was when you said you could manually squeeze the primer bulb and the motor would pick up. I would inspect the fuel pump and fuel lines for any air leaks as well. Many fuel pumps can be rebuilt with a kit, which you can probably get here at iboats as well.

I gotta go with fuel pump on this one too....I am thinking it wouldn't periodically run OK if carbs were screwed up. I just replaced fuel pump on my Yam 50, you can buy parts, but whole pump is about $45-$50. There are several aftermarket ones too for a few bucks less. My problem is a little different, and I incorrectly replaced fuel pump because I forgot to try the "pumping the ball" move while it was acting up. BTW, you can change fuel pump in about 5-10 minutes.