90 yamaha jet needs help

[fishonjon]

Moter runs /starts/idles fine. when you take off. It hits 5800 rpm instantly drops to42/45 00 rpm. bogged in the hole. acts like rev limiter but moter never hits 6Grand ??? aney ideas??? thanks

[fishkisser]

A new 2 stroke yamaha 90 propped is only rated to 4500 - 5500 max rpms ...
Sounds like thats all you should really expect out of it to Me ...
You might get a little more if you have a stainless impeller and go to an aluminum one ...
Good Luck and grease the bearings every other trip ...
Barney...

[fishonjon]

A new 2 stroke yamaha 90 propped is only rated to 4500 - 5500 max rpms ...
Sounds like thats all you should really expect out of it to Me ...
You might get a little more if you have a stainless impeller and go to an aluminum one ...
Good Luck and grease the bearings every other trip ...
Barney...
Thanks barney! this moter ran at about 56/58 for 10 years now the boat won,t plane. it jumps then just falls on its face. stays in the hole.

[fishkisser]

Thanks barney! this moter ran at about 56/58 for 10 years now the boat won,t plane. it jumps then just falls on its face. stays in the hole.

Wow thats odd jon ... How about the ignition wires and the plugs ?
At the same time you could do a compression check should be 90 -110 or so poor compression in a hole or 2 will take the poop out of her ...
Only other thing I can think of is old fuel / mix or a restriction in the high speed jet or fuel filter ...
Good luck recovering your R.P.M.s... Tight Lines ...

[fishonjon]

Did all that. plugs / comp test / fuel pump test / complete fuel system flush from carb to tank. R/R carbs impeller sleeve/ timed. took it to five star shop they told me it was done. all they did was what I told them I already did. Charged me 552.00 motor no better. thats y im asking for help.

[KingFisher85]

sounds like she might be wanting more fuel. Check the gas lines. 10 year old gas lines sounds like they should be replaced. I'm not talking about the gas line going from your tank to your motor but the gas lines around your fuel pump, block, carbs, etc.
Could have a small pin hole or a cracked line.
Just something to look at.

[fishonjon]

Did that vac tested complete fule system. thanks

[fishonjon]

Nobody else intrested in taking a shot at this?

[Boat Doc']

Make sure the reverse cup is adjusted correctly, it may be popping up.

[fishonjon]

Make sure the reverse cup is adjusted correctly, it may be popping up.Thank you tried that. if it was doing that. Moter would stay at 56/5800 rpm??? It just woudent plane right?

[tyeeterror]

I had a direct short once at the battery, and it blew my rev limiter. It sounds like what your expierencing. My 2 stroke would run fine up to about 3500 rpm, and then it would crap out, and come off plane. It would speed up and slow on its own. It ran fine up to 3500 rpm. I took it to the shop, and it checked out ok in the tank. We had to actually go out on the water with the mechanic to determine that was what it was. There is a way to disconnect it I have been told, to check it. You would have to ask a mechanic on that one.

[budnate]

try unplugging the tach and try it again, they can short out weird at times.:twocents:

[negoc8]

I have no real experience with Yamaha motors, but I did have a 4 cly merc that had two electronic control units, one for the top two cylinders and one for the bottom two. In the upper RPM's the ECU for the lower two cylinders would stop working. It's a long shot but an idea.
If you have a timing light with an inductive pick up, you can clamp it around one plug wire at a time and test individual cylinders for spark while actually under load.
Is that clear as mud or what!:cool:

[fishonjon]

:cheers: :applause: :cheers: Thanks guys. Tyeeterror / thats what I thought. Rev lmiter My problem I have only found parts changers. Not a diagnostic mechanic I already got soaked by A 5 star shop. so I dont know who to ask. Budnate no tac matco timing light. Thank you. Negoc8 Cheaked all 3. all drop at same time. I really appreciate all your guys Input. thank you . thank you . thank you. :applause: :cheers: :applause: :cheers: