RPM problems.....200Vmax

[Charger]

Hey guys, my 98 200Vmax EFI will not go past 5200 rpms and I lost speed. I noticed this the last few times I have had her out.

A few people have stated it was due to the hot weather, but Sunday morning it was kinda cool with a water temp of 82.

The throttle will respond up to say 60-70% throttle, but has no effect goin past that to full throttle. When the engine gets to 5000-5200 rpms, it stays there for a bit and will drop back and forth from 4800-5200 without moving the throttle. Of course the speed is down from near 70 to 61-62 mph. Thats all I can get out of her.

SOmeone also mentioned it could be the fuel filter. I popped the hood yesterday, the clear fuel bowl is full of fuel, I see no sediment in the bowl. Should I replace the filter inside the bowl? Is that the only fuel filter on the engine?

I am a mechanic by trade and I want to do all I can before I have to see a marine mechanic.
All input appreciated.


Modified by Charger4404spd at 9:01 PM 8/2/2006

[SWayne]

It sounds like the power pack to me. I have a 98 and it did the same, rated for 6000 rpms, was slow to get on plane and would only run 5200 rpms. Had it checked and replaced power pack, back in business.

[Bryan Hester]

just got my 2005 250 hpdi back from the shop was doing the same thing and they said that the throttle and shift cables needed to be adjusted. They adjusted them and now runs fine.

[21XDC]

I would replace the plugs and see if thats it. They are known for fouling especially if the oil pump linkage has not been adjusted..... Thats my bet.

[Charger]

I did pull the plugs. They look really good. I also just removed the fuel filter. It was clean and I can blow through it with ease.
It does come out of the hole good, heck she runs great, just wont get to max rpm's. Can the linkage go out of adjustment all at once?

[21XDC]

Mine "looked good" too... They were fouled. I put new plugs in and gained 10 mph Happened a few times to me on different Yamaha motors.

[Charger]

Ok you talked me into a new set of plugs. You work for NGK huh?
I will post the results!

[BuzzB8]

I'm not totally in agreement with Mike as to the cure, but I can verify that good looking plugs may not be performing up to par. I used to change them twice a year, but this spring I switched to the next hotter plug and I've been very pleased with the results...not fouling as much. Hell, I haven't fouled out yet!

Mike, Red/White, eh?

[21XDC]

I also run one plug hotter than the specs call for per Hydrotec's reccomendation. I have been running the br8hs10s instead of br9hs10s.... The NGK's get hotter the lower the number, Opposite of most plug companies. No fouling any longer.

Please respond with the results....

[Charger]

Picked up a set of 8's today. Will see if this clears the problem this week.

[21XDC]

You can get those plugs cheap at Advanced Auto.... I hope this is the fix.

[Charger]

Just installed them. Fixing to go to lake and see what happens.
The plugs that were in the motor were Bosch Platinum 2's. The reach on them was alot longer than the NGK's. Not sure why the previous owner used those.

[21XDC]

He probably had fouling issues.... Thats a good guess.

[Charger]

Well guys I wished you all had of been right on the fouled plugs.
Just got home from the water. Shes slower than she was before I changed plugs. No kiddin.
Fastest mph was mid to upper 50's and would only turn 5000 rpms, and really had to play with the trim to get that. I have a feeling now whatever it is is going to cost alot of money.

Do Yamaha dealers have a diagnostic computer they can hookup to her or what?
What should I do now? I welcome all suggestions.

[Phami1]

This may sound silly but my 06 200 vmax just had what sounds like the problem...I found the plastic clip (that holds the throttle and shifter cables) just inside the cowl was loose and allowed the cable to move and not give me full throttle. At times I couldn't get more than 1500 rpm out of it. It's worth a look before you go to the dealer.

[21XDC]

Have someone push your hotfoot to the floor if you have one and see if the throttle plates are open all the way. These motors also have a reputation for leaking fuel pump diaphrams.... This is something you can check and do yourself. Bad primer bulb also can do some weird things, Make sure you can pump it full and firm. Thats a $5.00 item that cant be over looked. At $90.00 per hour shop time, I'd do a lil' checking on these first.

[Charger]

Good idea, I will check that tomorrow.

[reelman]

A leaky fuel diaphragm will do that I think... at least it did for me... they are cheap too...
plugs are the 1st easy try for some issues.

[toledo bend jim]

Charger if you have O2 sensors like my '99 225 VMAX that,s what it sounds exactly like. Mine did the same thing and Yamaha put in new sensors and cleaned the transfer tube and it ran like a spotted a$$ ape. Just a thought. HTH Jim

[21XDC]

O2 cleaning... http://www.boatsetup.com/O2sensor.pdf