Is it the carbs?

[harvey5560]

Hello,

I have a 2006 50HP Yamaha 2 stroke outboard which I purchased last year. So far this season it has run great ( 35 MPH on my 16 foot aluminum) which is what is expected based on the published yamaha performance specs.

However, this past weekend I was only able to get up to 25 MPH both with the wind and against it in relatively calm waters. The motor started up right away, idled smootlybut didnt seem to be running on 100 percent power. RPM appeared to be about 15 percent less than I usually see.

When I purchased the boat last year the carbs were pulled and cleaned. Prior to storage I filled the tank with fresh fuel and used the recommended amount of Sta-bil marine.

Could this be the carbs or is there something else I should check?

Thanks

 

[99yam40]

Re: Is it the carbs?

You will have to do some testing to be sure.
Compression, spark, and timing. The last 2 at problem RPM also
If all is in spec then look into the fuel side
Carbs, pump, fuel restriction, or sucking air

 

[harvey5560]

Re: Is it the carbs?

Thank you.

I will check the spark tommorow. Unfortunately I do not have the equipment to check the compression or the timing.
Im also going to drain all the fuel out and replace with fresh and some seafoam to see if that does the trick.

Otherwise I will have to take the boat to get serviced.

 

[99yam40]

Re: Is it the carbs?

If it is running lean on any cylinder and you keep running it , it will do major damage to the motor.

A Yamaha service manual and the proper test equipment is cheap compared to taking it to someone or popping a piston by running lean

 

[harvey5560]

Re: Is it the carbs?

Thanks for the advice,

I may take it in for serivce then.

The quote I got from my local Yamaha dealer was 3 hours labout at $95.00 per hour plus$245.00 for a carb kit.

That seems awfully expensive compared to some of the things I've read on this site.

I have also ordered a service manual. Once I receive that I'll see how difficult it is to do it myself.

 

[wile.e.1]

Re: Is it the carbs?

I have the same motor and had the same problem, the bottom spark plug wire was loose, Dont know why , (even searched here to find an answer but had no luck ) I am sure you probably checked but try re seating the plug caps. I had the same symptoms, starts and runs fine..just lost some of the top end. Good luck to you

 

[harvey5560]

Re: Is it the carbs?

Well I have taken the outboard to be serviced today to hopefully resolve the problem.

Can somebody please advise what the compression should be on this outboard?. I tested it and got 90 PSI on all cylinders.

thanks

 

[mphelle8vld]

Re: Is it the carbs?

I have an 88 and 89 50hp and they have always been around 120psi but there are a lot of variables to that test. Looking at your first post it sounds more like carbs or ignition.