WMK39 Carbs.,adjusting & AutoBlend ???

[vnvet72]

1986 90hp six. Still needing advice on the final adjustments for lean/rich settings. The SELOC manual I'm using describes in water adjusting via RPM's and in gear but the boat has NO tachometer which is another point of concern. So any recommendation for a tach. and wire connection will also be appreciated.

In my previous post, I stated that the boat sat for many years before I rebuilt the carbs but now, after the rebuilds the engine smokes BAD w whereas it didn't so much prior to rebuilding, it only ran rough. Now, it does run and idle much better but has not yet been in the water, only a flushing barrel.

ALSO, this boat has the Auto-Blend that one individual related it being a horror story. Owner has never had any problems in the past. Any other facts on that would be appreciated as well.

I am dumping the old red oil out (Johnson O/B oil) and putting Amsoil HP injector oil into it which is the same oil I use in my own boat w/225 Optimax. It's a clean runner. Although, I don't feel the oil is so much the main issue with the 90hp smoking bad.

Thanks for any help from those with the experience in 90/115Hp's w/ WMK39 carbs.

 

[Chris1956]

Re: WMK39 Carbs.,adjusting & AutoBlend ???

I lot of folks recommend dumping Autoblend. I have no experience with it, so won't offer an opinion.

Without any experience with that motor, it will be hard to determine RPMS w/o a Tach. Any aftermarket OB Tach will work. If it were me, I would leave the timing and throttle stop where that are and adjust the mixture settings to give smooth idle. As long as the idle is 1000RPM or less, shifting into gear will feel normal to you. If it clunks more than normal, drop the RPMs.

You will likely need to richen the idle adjustments (CCW) to allow the motor to accelerate, so open them 1/8 turn, starting on the top carb, then proceeding to the mid carb and then bottom carb, testing acceleration after each adjustment. Whne you get reasonable idle and smooth acceleration, you are done.

You should use a TCW-III rated 2 cycle oil in that motor.

 

[daveswaves]

Re: WMK39 Carbs.,adjusting & AutoBlend ???

Chris is right on with the suggestions. You can get a low smoke TCW -111 outboard oil as well. The autoblend is OK when its working....when it fails it usually takes the engine with it, hence the recommendation to dump it and mix the oil with your gas, 50 to 1.

 

[vnvet72]

Re: WMK39 Carbs.,adjusting & AutoBlend ???

I flushed out the Autoblend with clean fuel and drained it well which had old red Johnson O/B oil in it that the owner had previously mentioned being "OK". Out came globules of icky stuff and it's a wonder it even ran when I first started it after sitting for so long.

I added fresh Amsoil HP injector oil to the Autoblend, I've used Amsoil exclusively for all my lubes since 1975 and swear by it. Filled up the tank w/ fresh premium gas (owner never used premium) and it now runs and idles like a new engine in the flush tank with NO smoke.

I tweaked the carb adjustments as mentioned but for the most part, they were already at their sweet spots so I left as is, approximately out 1-1/2 turns. The next test will be to put the boat in the water on the trailer and under load, hopefully with a tachometer installed.

The hardest part of working on the carbs I found was taking them off and reinstalling until I realized, its so much easier getting at the starboard nut with the float bowl caps off which allows more room for a socket and wrench.

Needless to say, my retired friend was elated and we can't wait to get back out on the Puget Sound and dropping our lines for salmon and ling cod again.


Mercury really makes a fine machine.

Thanks guys for all your input.

 

[daveswaves]

Re: WMK39 Carbs.,adjusting & AutoBlend ???

I flushed out the Autoblend with clean fuel and drained it well which had old red Johnson O/B oil in it that the owner had previously mentioned being "OK". Out came globules of icky stuff and it's a wonder it even ran when I first started it after sitting for so long.

I added fresh Amsoil HP injector oil to the Autoblend, I've used Amsoil exclusively for all my lubes since 1975 and swear by it. Filled up the tank w/ fresh premium gas (owner never used premium) and it now runs and idles like a new engine in the flush tank with NO smoke.

I tweaked the carb adjustments as mentioned but for the most part, they were already at their sweet spots so I left as is, approximately out 1-1/2 turns. The next test will be to put the boat in the water on the trailer and under load, hopefully with a tachometer installed.

The hardest part of working on the carbs I found was taking them off and reinstalling until I realized, its so much easier getting at the starboard nut with the float bowl caps off which allows more room for a socket and wrench.

Needless to say, my retired friend was elated and we can't wait to get back out on the Puget Sound and dropping our lines for salmon and ling cod again.


Mercury really makes a fine machine.

Thanks guys for all your input.

You are likely going to have to back those carbs out a minimum of half a turn more. If it runs "sweet" in the barrel it is too lean for the lake. Sounds like you are on your way.

 

[vnvet72]

Re: WMK39 Carbs.,adjusting & AutoBlend ???

Thanks Dave.