96 Yamaha 90 Surging

AaronC2

Recruit
Joined
Aug 2, 2006
Messages
3
Hi there, Hopefully one of you experts can help. First of all the motor had been running fine. It was the first time it ran in about 2 years. It was running strong then I hit a big wake and shortly after that it droped to about 3000rpm. It ran smooth though. I stopped for a minnute then tried to go again. It goes up to that point then it pulses about 500rpm. It doesnt cough like its out of fuel.
I took it home and ran it on the hose. It still does it. It surges between 3000 to 3500. then it will hold 4000rpm but when I try to give it more throttle it does the same thing between 4000 and 4500. I've gone through the Carbs and all the lines. I don't think its in the fuel system but I'm no expert. I've tested all the Coils. They are all within their paramiters except the charge coil. It is 1150 ohm instead of 850 and 44 instead of 120. Can the charge coil cause this problem.
It starts and idles fine. Am I missing something? Any suggestions would be greatly appreciated.
 

Ray Neudecker

Lieutenant Commander
Joined
May 25, 2004
Messages
1,656
Re: 96 Yamaha 90 Surging

Definitely soundslike a fuel restrition. Have you changed the fuel pump?
 

AaronC2

Recruit
Joined
Aug 2, 2006
Messages
3
Re: 96 Yamaha 90 Surging

No, I havent changed the fuel pump yet. I did take it apart and it all looked good. ONe thing I did try was squeezing the bulb while it was doing that and it didn't seem to make a difference. That was just one suggestion someone gave me. Someone mentioned a anti siphon valve but I have no idea where it would be.

Thanks for the feed back!!
 

Ray Neudecker

Lieutenant Commander
Joined
May 25, 2004
Messages
1,656
Re: 96 Yamaha 90 Surging

The anti siphon valve is located in the barb at the fuel tank. It has been a source of fuel restrictions in the past.
 

bernieb

Petty Officer 1st Class
Joined
Feb 9, 2003
Messages
209
Re: 96 Yamaha 90 Surging

Motor sat for two years you say. Best to clean out main tank with a cleaner as minute particals may be getting into your clean carbs. Are you using a water/separater screw on filter in the boat? Hey Ray can he bottle spray some pre-mix in the carbs while running to locate the weak carb ?
 

AaronC2

Recruit
Joined
Aug 2, 2006
Messages
3
Re: 96 Yamaha 90 Surging

Thanks guys, The boat is brand new. I got the motor with another boat. Not to say the new tank couldnt have had anything in it but all the fuel is fresh. The tank on this boat is built in. It was the Hewes dealer that mentioned the anti siphon valve. Maybe they are prone to this problem. I'm off to go get an external tank to see if it makes a differance. The boat is an 06 Hewescraft 18' Sportsman if anybody has heard of any problems.
 
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