50HP Yamaha 2-stroke low RPM at WOT

[ltpapin]

I have a 50 HP yamaha 2 stroke manufactured 12/2007 model 50tlr that only reaches roughly 3000 RPM at WOT. I got this boat 6 months ago used. It has always exhibited this behavior since I've owned it.

So far here is the troubleshooting I've done:
1. New 92 octane non-oxygenated gas.
2. New spark plugs torqued properly at 18 ft/lbs.
3. New external fuel filter. (My boat uses the large size)
4. New internal fuel filter.
5. Went from the factory 11 5/8" x 12" prop to a 12" x 10" prop.
6. Checked cable adjustments. When the remote unit (model 703) is in the WOT position, the carbs are all fully opened.

The new prop didn't affect the max RPM at all even which really shocked me. It is almost as if this engine has a break in governor on it or something like that which only allows the RPM's to get to 3000.

The person who owned it before me most likely did not have a yamaha dealer do the 10 hour service when it was broken in.

Is there something with these motors that only allows them to to go 3000 RPM during break in that never got turned off?

This motor starts very easy after the first start of the day, does not miss, does not hesitate, and honestly runs like a swiss watch all the way up to 3000 RPM. It is a little grumpy about wanting the bulb on the fuel line pumped until firm and then several times after that for an easy first start of the day.

This is a 2 year old motor and it runs great other than I feel I should be getting more RPM's out of it.

Am I off my rocker, is this normal behavior? Should I just accept that this is all I get out of my motor?

Thoughts on what to try next? Suggestions? Comments? HELP??? !

Thank you.

 

[99yam40]

Re: 50HP Yamaha 2-stroke low RPM at WOT

what kind of boat and load are you running?
As always I would check the compression and spark and timing on a motor I was working on.

If all is good at problem RPM the look at the fuel side.
Maybe best to have shop check with a dyno or test prop to make sure the motor is putting out the HP it is designed to

 

[ltpapin]

Re: 50HP Yamaha 2-stroke low RPM at WOT

It's mounted on an alumacraft Classic 165 CS. 16' 5". This is a very common setup sold at several different dealerships in the area.

I can run roughly 3k RPM with just myself in the boat or with two other people and a 70lb dog on top of that.

That's the odd thing, changing the prop, changing the load, nothing I've done seems to make any difference at all which is the odd part.

That's why I was thinking governor or something along those lines possibly?

Any other thoughts, or suggestions?

 

[mphelle8vld]

Re: 50HP Yamaha 2-stroke low RPM at WOT

If you purchased a newer 50hp that would only run 3k, most likely the seller knew that his newer 50hp would only run at 3k. Listen to 99yam40 and test the compression, maybe we'll see you and the seller on The People's Court.

 

[droptheline]

Re: 50HP Yamaha 2-stroke low RPM at WOT

check to see if all cylinders are firing using an inductive timing light & spark gap tester if the light says all is good, sound to me like you might not be firing on all of them.

 

[ltpapin]

Re: 50HP Yamaha 2-stroke low RPM at WOT

So here is the verdict:

Compression is fine, timing was fine. It is developing full horsepower.

The main issue (drum roll please):
Yamaha uses the same TACH for all of it's engines. The TACH has a setting that needs to be set to the type of engine you have, in my case a 3 cylinder engine. From the factory it was setup for a 4 cylinder reading the tach as low.

I'd like to take credit for this but my had a local dealership check things over for me after it got out of my comfort zone.

While they were there they resynched the carbs and cables and went over all the adjustments for me and my hard starts went away now too.

If anyone else is having this problem it might not actually be a problem, it might just be the setting on your TACH.

I thought I'd close the loop on this one as many people seem to be having the issue without much in the way of a resolution.

Safe boating!

-Luke

 

[ahamay]

Re: 50HP Yamaha 2-stroke low RPM at WOT

happened to me from the dealership brand new. The change is from a 50hp to a 70hp. For a 50 it's set at a 4 pull. 70 and up is it 6 or 8. I wasn't happy .

 

[rodbolt]

Re: 50HP Yamaha 2-stroke low RPM at WOT

the tach does NOT set for 2,3,4 or 6 cylinders.
it sets by alternator poles.
and that tach may or may not fit ALL yamahas as some tachs cannot be set for a 4 pole alternator.
your 50 should set at 6 pole. from the factory since about 2002 the yamaha digital tachs are set for 4 stroke,12 pole and two wire trim sender.
make sure yours is set for 2 stroke,6 pole and two wire trim.
if set for 4 stroke the alarm visuals wont work correctly and will flash at you constantly.
the 70 sets at 6 pole.
if in doubt look at the tuneup spec guide.
it shows tach pole settings.
and yes we see a lot of poorly rigged boats that the tach was icorrectly set at installation, its not a yamaha problem.
its a problem with minimum wage monkeys that cant read.