200 OX66 Power Loss?

[trailertrash20010]

I have a 99 ox66 200 yamaha,and all the sudden while running it derates from 5600 rpm to 4500 to 4700 rpm sometimes if I let off the throttle for a few seconds and get back in it,its fine and other times nothing,also sometimes while running it'll pick back up on its own? I have replaced filters and plugs,also cleaned the O2 sensor and plunger which wasn't dirty. I have bypassed the cowl fuel fitting? I did notice that in the morning it runs fine until the sun comes out? After a long run 5 miles or more it idles bad,misfiring and barely will run?If I try pumping the primer bulb it stalls and won't start for 30-45 seconds,need help.

 

[TimC2520]

Re: 200 OX66 Power Loss?

How old are the low pressure fuel pumps?

 

[trailertrash20010]

Re: 200 OX66 Power Loss?

2yrs

 

[trailertrash20010]

Re: 200 OX66 Power Loss?

I took the 3 pumps off my outboard and disassembled them,I am a diesel tech not a marine tech so I see the rear diaphram on all pumps but how would I determine if there worn out? I did hold them to a light and found no holes?

 

[trailertrash20010]

Mr Humble with problems

Mr Humble with problems

Please is there someone out there with some advice for me? Thanks.

 

[cousinabe]

Re: 200 OX66 Power Loss?

have you cleaned the vst filter?
any more details on what you have done regarding maint would help too.

 

[ARCHSEA BUNKER]

Re: 200 OX66 Power Loss?

remove the vst tank, remove filter and soak in carb cleaner, use air jet or carb spray to clean the fine mesh . when you reasemble , the black gasket can be re used . you might have to put it in the ice box for 20 minutes if it swelled to much, hold in place with a little vasoline, start here first , i had the same symptons and this cured it ,sorry i forgot to say drain tank before you start and remove key from ign