Yamaha 150 ox66 efi problems

miket53

Recruit
Joined
Jun 23, 2004
Messages
1
Ive been reading the forum for a while and there is some really good info here. <br /><br />I have a 150 TRP OX66 efi. I use it mostly in saltwater. I take meticulous care of it. Water pump, plugs, fluid changes, filters, grease, oil clean, etc. I use this boat year round so there isn't any down time, maybe 4 weeks at max. Last time out, as soon as I cleared harbor and started to get on plane it had a severe bump or miss. I thought i had hit something. Checked around and nothing and started again and the same bump at about 3000 rpm. If I idled around no problem but if I tried to get on plane it would miss.<br />This is what I have looked at.<br />1. I thought it was the lower unit . So I drained lower unit. Perfect, not milky, no sign of metal shavings. Re torqued props, checked shift rod adjustment , all okay. <br />Tested , still has miss.<br />2. Removed Primary fuel pumps and pressure/vacuum tested. OK<br />I'm going to look at the VST system next. Am I on the right course ? I do have a Yamaha shop manual but the trouble shooting is limited. My son just got out of MMI in Orlando last year as a boat tech. He knows a whole lot more than the old man about this stuff. But Its hard to get him over to take care of my stuff working 50 -60 hr wk. He told me don't be messing with stuff till he could get over there. Smartalic kid! LOL Anyway I need some direction I need to get back on the water.<br />MikeT
 

tryan

Seaman
Joined
May 29, 2004
Messages
59
Re: Yamaha 150 ox66 efi problems

a buddy has the same motor and she started surging last few times out. we are going to try a little de-carb and see if that helps.<br /><br />the runs good at low rpm sounds like a fuel delivery issue. i would check the pick-up in the tank for an obstruction. you might run her on a smaller portable tank before jr comes to town and see if she still is limited to 3k. <br /><br />i experienced a total melt down of a c.d.i. box on a yami 80 hp 4 stroke a few weeks ago. ouch to the wallet on that one. look in your manual and see if disconecting the yellow wire under the cowl puts the brain box into limp mode.
 
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