1986 Yamaha 150 ETXJ Many Problems

[hemijosh426]

Hello, Im new to iboats, and it looks like a great wealth of information.
Ive been having problems on my 1986 25 foot wellcraft coastal with twin 150 v6s. I Have one motor running great and the other motor wants to load the plugs up with gas and is hard to start, and will only start on ether. All the plugs are wet when i pull them out. i have carb mixture screws at 2 turns out from stop. It will run great and 4500 rpms all day long once i am able to get it started. It will bog out a little and then light up to life and run great on upper rpms. This motor also does not seem to be charging its battery, as i have dual batterys on the boat and they are separated from one another. Once it shuts off its a bear to get started again. I replaced fuel pumps and rebuilt carbs on both motors and replaced quick disconnects on both motors and new NGK plugs. Does anyone have an idea of what it could be? Thanks, Josh

 

[scrampbell]

Re: 1986 Yamaha ETXJ Many Problems

Re: 1986 Yamaha ETXJ Many Problems

Hey Josh, you didn't say the HP of these motors -- i'm assuming 4 cylinders on each motor? I'd first start by checking the spark on a spark tester. You should get a thick blue spark at about 1/2 inch gap. This is the easiest thing to check and rule out, so go ahead and get it out of the way. Given your related electrical issue with the battery, it also makes sense to start here.

Let us know how it turns out.

Also, best advice given on iboats is to get a shop manual. You can check with your local library if you're cheap like me.

 

[hemijosh426]

Re: 1986 Yamaha ETXJ Many Problems

Re: 1986 Yamaha ETXJ Many Problems

I will check the spark later today. The motors are V6 1986 Yamaha ETXJ 150 hp. oil injected. One is counter rotating. Its weird how once the motor gets started and comes off idle it runs great. I have adjusted carbs once to 1 1/2 turns and then all the way to 2 1/2 turns and it does the same thing so i brought it to 2 turns from fully out. WOuld seafoam fix it?

 

[Safebet]

Re: 1986 Yamaha 150 ETXJ Many Problems

My 1985 150 HP ETLK has the air screws set at 1 1/4 turns. My manual recommends 1 to 1 1/4 turns.

 

[hemijosh426]

Re: 1986 Yamaha 150 ETXJ Many Problems

Thanks for the reply. I will redo my air screw's to 1 1/4 and see what happens. Just to make sure im adjusting the correct thing, each carb has 2 air screws correct? On either side of each other and a total of 6 for the motor? I thoought they were called mixture screws, could be air mixture screws. Just making sure theres an adjustment that im not missing. Would carbon build up cause my problems? Should i try seafoam? Thanks very much

 

[99yam40]

Re: 1986 Yamaha 150 ETXJ Many Problems

Did you adjust the linkage like the manual calls for after reinstalling the carbs?
You really need to pick up a service manual for your motor.

 

[hemijosh426]

Re: 1986 Yamaha 150 ETXJ Many Problems

I purchased a manual from e-bay and the guy wont return my emails now, i started the refund process with pay pal. How would you adjust the linkage? i tried to be carfeul taking it off to not mess up any adjustments

 

[rodbolt]

Re: 1986 Yamaha 150 ETXJ Many Problems

test spart,do a forum search on a home made spark tester,make one.
test compression.
if the above pass fix your fuel system.
look carefully at your carb diagram.
if it lists both a pilot fuel jet and a pilot air jet you dont have air fuel mixture screws.