Yamaha ox66 issues

[striper56]

Here is the update on the still not running correctly motor. I installed 3 new LP pumps. The motor sounds better but still cutting out when increasing or decreasing the rpms from 3000 rpm down to 2000. I took a 6 gallon tank with me and connected it to the LP pump. Still didn't run correctly.
One time I shut the motor off and could not get it to start. It sounded like the kill switch was disconnected but was not. Tried a few more times still nada. Went back pumped the primer ball switched the battery to both and it fired right up and ran fine.
Great website VancouverPotter23. I will add it my favorites.

Thanks

[striper56]

This afternoon I was testing the TPS the motor would not start. I checked the primer ball it was soft more like empty. Pumped the ball for a few minutes until the ball was hard and it fired right up.

[Old'sCool]

Still sounds like a fuel supply issue.

[afterhours]

I agree with oldscool. Sounds like you've got a fuel delivery problem between your bulb and the vst. When you pump your bulb you are filling your vst and pressurizing the line between the vst and your bulb and the engine behaves. Then the line loses pressure for some reason. Try 3-100-101 in that link to boatinfo. If you have a vacuum gauge, you can stick it in line at various points to check for faulty pumps, air leaks, etc. If you have an air leak, some clear plastic line might show bubbles.

[striper56]

I did see some small air bubbles in the clear filter on the engine block when it was refilling. I was running the motor and noticed the filter would go down half an inch then when filling I did see air bubbles.

[uncleboo]

Not for nothing, but, I had an issue with the downstream check valve in a primer bulb. I could pump the bulb up tight, but at some point the ball would stick cutting fuel flow off. I was seeing bubbles and some gas through the in line filter but motor wouldn't stay running. Replaced the bulb and haven't had a problem since.

[Vezo, Part II]

I learned a long time ago that an aftermarket bulb can appear perfectly fine. Now ONLY OEM! One place not to play with every other Chinese rubber available. Cheap starting point, especially if you are using same fuel line and primer bulb when switching to six gallon fresh tank on deck. Maybe this will help.

Vezo

[striper56]

I bought the primer ball from West Marine $29.99. I think they had a West Marine brand that I did not will not buy. I think it was a Mercury primer ball. I was having the problem before and after replacing all of the fuel line and primer ball.
I hooked the 6 gallon tank directly to the LP pump and the engine still would cut out when increasing or decreasing the rpms mostly between 2000 and 2400 rpms.

[Capt Terry]

As an update to my 5-18-18 post removing the anti-siphon valve and partially blocked air vent screen dropped the vacuum gage reading from 4"Hg after a partial throttle run to 2"Hg after a WOT run. I concur with some of these other remarks, after issues through the years I only use OEM fuel bulbs. And even with that replace them before you think you need to. Once couldn't keep my Merc running back to the ramp without continually squeezing the bulb.

[striper56]

First let me thank every one for all the great info and help trying to fix figure out my issue. I learned a lot about the fuel system. It ended up being the little filter on the high pressure pump. After reading about the HP pump I tested for the correct voltage 9v at idle which was good and testing the pressure which was good 35. I found the issue. The little filter on the HP pump was clogged. I washed it off with carb cleaner reinstalled the filter put the VST back together and she ran perfectly. Good for another 1700 hours. Thanks again!