50 yamaha WOT only 4000

[bquinlan]

I have a 16ft Lakesport center console (750 lbs) with a 50hp 2 stroke. My WOT is 4000 RPM and 26MPH. I have a 10.25x14 stainless prop. I've been told by several people that i should be able to run in the mid 30s. If in neutral it will rev to 6k+. I was able to barrow a prop from friend its 11 5/8x11 with his prop i was able to get my RPM up to 5600 but my MPH dropped to 23.

Ive been told it may be a motor problem but she starts right up idles great and runs like a champ until she hits 26-27 at 4K.

Ive check plugs and shes getting spark on all 3 cylinders. Fuel screen is clean so i don't think its a carb problem i cleaned the carbs about a year ago due to not getting fuel turns out it was a bad fuel line from tank to motor.


IF anyone has had this issue your knowledge will be greatly appreciated.

Thanks

[Rlilleaas]

You can try to google for "prop calculator" and calculate speed.

Perhaps you could use your first propellar and lift the engine slightly? Physically lift it where it is installed on the stern.

Is the boat clean underneath and no water trapped inside?

Your engine sounds fresh enough to me

[bquinlan]

Thanks for the reply I will see what I can find on prop calculators.

I forgot to mention in my first post that I did move the motor up on the transom the cavitation plate was even with the bottom of the boat now it's sitting about an inch and a half above the bottom. Very little difference maybe 100 RPMS.

The underside of the boat is clean and no water trapped inside. I personally don't think it's a motor issue but I've talked to a few prop shops and they are telling me I should beable to turn my 10.25x14 all day long.

[Rlilleaas]

assume you have played with the trim? Any damages to the prot. Not sure what the WOT range should be on this motor. Check that also

[ausnoelm]

Did it ever rev to max RPM, and this just happened? Do not rev it in neutral, it proves nothing at all.

[ausnoelm]

OH, and forget the speed, it will just add something else for you to fool around with, get your RPM right, and go boating.

[99yam40]

what HP motor is max the boat rated for?
sounds like hull is too heavy for some reason since RPM did come up with the other prop
Only way to see if hull is water logged is weigh it.
drive onto scales and then start subtracting tow vehicle ,trailer, motor ,gas, batteries, and anything else you have in it to see if hull is what it should be.

check with a Yamaha shop to see if they have a test prop for your motor to run it in tank to see if motor has a problem.
if motor is good them you are left with a mounting or hull problem.

here is a place to look for a rig close to what you have . see what prop they used and what RPM and speed they got.

Outboard Performance, Performance Bulletins | Yamaha Outboards

Look at this one to see if it is close if you cannot find your boat
http://yamahaoutboards.com/sites/def...16cc-50tlr.pdf

[cpostis]

I don't think prop problem. I don't think hull too heavy problem (your boat is an aluminum hull).

Go back to basics, I'd start by following by performing periodic maintenance in sequence as published in Yamaha Service Manual for your motor (I also have a Seloc Repair Manual that describes procedures in more detail than Yamaha's Manual, although more general across a variety of Yamaha motors in a range):

PERIODIC SERVICE/FUEL SYSTEM
CONTROL SYSTEM
Throttle link adjustment
Throttle cable adjustment
Shift cable adjustment

After this is done, and if you still have problems, then you should systematically diagnose. Again, use the procedures outlined in you manual.
I believe your issues are fuel system related.

Have you checked/replaced your fuel pump? Are your carburetor butterflies opening completely? Should your carbs be cleaned again?

If you can give me your exact complete model # of your motor, I may be able to send you exact procedures. I'll Private Message you if you request.

[bquinlan]

I don't think prop problem. I don't think hull too heavy problem (your boat is an aluminum hull).

Go back to basics, I'd start by following by performing periodic maintenance in sequence as published in Yamaha Service Manual for your motor (I also have a Seloc Repair Manual that describes procedures in more detail than Yamaha's Manual, although more general across a variety of Yamaha motors in a range):

PERIODIC SERVICE/FUEL SYSTEM
CONTROL SYSTEM
Throttle link adjustment
Throttle cable adjustment
Shift cable adjustment

After this is done, and if you still have problems, then you should systematically diagnose. Again, use the procedures outlined in you manual.
I believe your issues are fuel system related.

Have you checked/replaced your fuel pump? Are your carburetor butterflies opening completely? Should your carbs be cleaned again?

If you can give me your exact complete model # of your motor, I may be able to send you exact procedures. I'll Private Message you if you request.

Thanks for your help yes it is an aluminum hull.
carburetor butterflies are opening full, throttle link,throttle cable, and shift cable all seem to be working fine. I have not messed with fuel pump i guess i will look into that i checked the fuel filter on the motor yesterday and it was clean so i doubt the carbs are dirty again but i guess i will pull them off and give them another cleaning.

Complete model number is 50TLR 6H5K L 1009843

[99yam40]

part of link and sync when putting carbs back on is checking to make sure timing is in spec at idle and WOT. make sure you follow link and sync procedure in service manual is followed every time you reinstall the carbs


Did you look at the links on performance bulletins I posted?

Is there another letter on the end of the 50TLR or is it a newer than 2005 motor?

[bquinlan]

part of link and sync when putting carbs back on is checking to make sure timing is in spec at idle and WOT. make sure you follow link and sync procedure in service manual is followed every time you reinstall the carbs


Did you look at the links on performance bulletins I posted?

Is there another letter on the end of the 50TLR or is it a newer than 2005 motor?

Im going to go out today and get a timing light so i can check time.

Ive check out the performance bulletins according to that seems to me its a motor issue

There are no other letters at the end of 50TLR the motor says 8/05 but when i bought i was told it was a 2006. i figured since it was late in the year they rounded it to the next year.

[cpostis]

Im going to go out today and get a timing light so i can check time.

Ive check out the performance bulletins according to that seems to me its a motor issue

There are no other letters at the end of 50TLR the motor says 8/05 but when i bought i was told it was a 2006. i figured since it was late in the year they rounded it to the next year.

Yep, Yamaha deleted the fourth digit for this motor beginning 2006 model year (in your case 8/05 is a 2006 model year). I checked a few part #'s between 2002-2005 and 2006 motors. Most are the same, but the CDI unit is different.
The manual I have is for a 2004, therefore these pages may not necessarily show you your particular procedures and/or specifications. If you want, private message me with your e-mail and I will send you the pages for a general idea what needs to be done. You should get an appropriate manual if you don't have one. As 99Yam said, "make sure you follow link and sync procedure in service manual is followed every time you reinstall the carbs" Timing procedures are covered under the throttle link adjustment section of Periodic Service I sent you before.:

PERIODIC SERVICE/FUEL SYSTEM
CONTROL SYSTEM
Throttle link adjustment
Throttle cable adjustment
Shift cable adjustment

The procedures must be done in the sequence stated in The Yamaha Service Manual.

You do not necessarily need a timing light unless you just want to confirm timing. There are marks on your linkages that put timing on the mark if adjusted per procedures.

Notice how many times I say "procedures".

Get the Manual!

[ausnoelm]

Did it ever rev to max RPM, and this just happened? Do not rev it in neutral, it proves nothing at all.

You still didn't tell us if it ever went OK, is it a secret or something? Makes a huge difference to how you approach this problem if it went OK before.

[bquinlan]

You still didn't tell us if it ever went OK, is it a secret or something? Makes a huge difference to how you approach this problem if it went OK before.

When I bought the boat the tach did not work I finally replaced the tach within the last month so now I'm able to know the RPMS since I've had the boat it has always ran in the 26-27MPH at WOT. I've always thought it was a little slow but just figured it it was a heavy boat.

[99yam40]

You do not necessarily need a timing light unless you just want to confirm timing. There are marks on your linkages that put timing on the mark if adjusted per procedures.

Notice how many times I say "procedures".

Get the Manual!

I had to replace the CDI on my C40 due to the idle timing was way off (14 BTDC instead of 7) when I 1st got this used motor.(also found someone had drilled out the main jets to a larger size, you never know what you will find when getting a used motor)
throttle linkage adjustments had been made to try to get the idle timing up due to the retarded timing. adjusting the stopper and wiper linkage messed up the over all timing.

I am Just saying that just because the wiper is pointed to the marks when it should does not mean the timing is correct even thou it should be. Always best to verify