'01 J90 60 deg 2 stroke Idle/low rpm

[captmello]

I just took out my new to me pontoon listed in my sig.

I noticed that at rpms under 2000 the motor puts out a lot of vibration. Once it gets over 2000 rpm, it smooths out nicely and runs good.

Being a pontoon, slow speed cruising is common and i'm wondering if this is just the nature of a two stroke, or if I may be able to smooth it out a bit with some adjustment.

I plan to do a decarb on the motor as soon as I learn how. Could this help with the low rpm rough running? Spark plugs are new, what else is there?

I'm new to two strokes so any advice or info is appreciated.

 

[jeffersondodson561]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

How long has this been sitting? On a pig like a pontoon I would think that 2000 is right where your transition/intermediate circuit of your carbs is taking over, possible carbs overhaul?

 

[captmello]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

Thanks for the response. It had been sitting over the winter, as far as I know. The carbs also leak quite a bit of fuel. I'm told this is common, but it really pours out once the engine it tilted up.

I took the boat out three days in a row now. I started with 1/2 tank of old fuel. I topped it off with new gas, and ran only about 4 gallons through, 1/4 tank. I then topped off the tank again and burned about 1/3 of it in the last two days.

Not only does it run rough at idle, up to 2000 rpm, it is also having a random miss through out all rpm ranges. But the miss/hesitation is worse sometimes, and sometimes it goes away for hours. It is not prop cavitation. It really feels like a fuel issue.

I'm new to outboards but I'm a pretty good wrench. I'm thinking a carb rebuild is in order. The engine is all original. I just replaced the impeller for the first time.

I'd really like to take this one step at a time before I start throwing parts at it, and starting projects I can't finish.

What do you think? I read up on rebuilding the carbs. It looks okay, kits are cheap.
any other suggestions on trouble shooting?

 

[jeffersondodson561]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

The carbs also leak quite a bit of fuel. I'm told this is common, but it really pours out once the engine it tilted up.

This is only common to people who say it is common. Once you get your carbs rebuilt you need to run fuel stabilizer every time you fill up. If you can get creative and drain the carbs after every use you can protect yourself from future problems. Today's gas starts to deteriorate in about 3 weeks, your fuel stabilizer protects the gas from "gumming" up but it only works with new gasoline, it's a chemical reaction so if you try to use it on old gas you are wasting your time. And it only protects the gas from tarnishing key points of the fuel system it does not protect your octane level. So if you stabilize your gas one season and run it the next put in some octane boost (which contains mostly alcohol) or fill up with the premium gas. These are all precautions to take to avoid problems, but 85% of the problems we see are fuel related.

 

[captmello]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

Thanks for the advise. I just ordered 4 carb kits. I'll post back the results of the rebuilds when I get done.

Any advise on the rebuild would be great. My manual mentions needing an OMC Orifice Driver, part # 317002. Is this necessary or is there a common substitute? I want to do this right the first time.

 

[jeffersondodson561]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

Get it!

 

[captmello]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

Get it!

Got it! Thanks for all your help.

It's been a couple weeks now and I've removed the Carb Bodies but decided to leave the throttle bodies in place as I don't want to mess up the synchronization. This may not be the proper way but I'm hoping it will work. Once I finished going through all the carbs, cleaning and reassembly, I noticed the float bowls are all warped and will not seal to the carb bodies, so I've ordered 4 new float bowls.

Am I wrong for not pulling the throttle body's? As an outboard newbee, I'm trying not to get in over my head.

Any advice on my methods? Should I be pulling the throttle bodies?

Thanks.

 

[captmello]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

I'm also wondering what to replace the zip ties that hold the fuel lines with, that I cut to remove the carbs. New zip ties? or is there something better?

 

[jeffersondodson561]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

Mercury P/N 54816311T about .25/each. What I do is get a 1/4" box end wrench and route the cable end thru the zip tie and put the box end over the tail and push towards the tie while you pull on the end with vise grips adjusted just enough to grab without slipping. Try and get that last "click" on the tie strap before it breaks. Do not allow the tie straps to sit in the sun or they will become malable and not tighten securely. Clip the end with small dikes to make pretty. Put these on all fuel fittings! You will understand why when you examine tie strap.

 

[captmello]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

thanks for your reply. I will find a merc dealer and pick some up for the reassembly.

If you have a chance, could you comment on my prior post, post #7.

Just trying to get a Pros opinion.

Thanks again for all your help.

 

[jeffersondodson561]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

Got it! Thanks for all your help.

It's been a couple weeks now and I've removed the Carb Bodies but decided to leave the throttle bodies in place as I don't want to mess up the synchronization. This may not be the proper way but I'm hoping it will work. Once I finished going through all the carbs, cleaning and reassembly, I noticed the float bowls are all warped and will not seal to the carb bodies, so I've ordered 4 new float bowls.

Am I wrong for not pulling the throttle body's? As an outboard newbee, I'm trying not to get in over my head.

Any advice on my methods? Should I be pulling the throttle bodies?

Thanks.

The proper way is to order new bowls, however I have on a couple of occasions sanded them down on a perfectly flat surface (we used 18"x18" piece of slate with 220 grit sandpaper in a figure 8 motion) sand it down lightly until you see the abrasive contact on all portions of the bowl gasket sealing area you need to be sure that you apply even force. But since you have ordered new ones that is the way to go.

 

[captmello]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

Thanks a lot, again, thats nice to hear, regarding the new float bowls. I want to do it properly.

What about the throttle bodies? I left them on because I'm afraid of resyncing the carbs.

I was thinking of pulling the idle needle and spring to spray some cleaner into the hole. Is that useful? Would I simply seat the idle screw and count the turns, before removing?

Thanks again for your help. What else would be a good idea to do while i'm in there to do it "properly".

 

[jeffersondodson561]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

Lightly turn in the mixture screw while counting the number of turns until you feel it lightly seat. So grip the screwdriver handle lightly so it acts as a "clutch" when the needle seats in the orfice. Record the number of turns it took to seat the needle. This will give you a reference starting point if they were set up correctly to begin with. Then once number of turns is recorded remove the mixture screw and blast with carb spray. OMC uses idle air mixtures more than any other manufacturer, just be aware of this when it comes time to adjust idle rpm.

 

[bob johnson]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

I have a similar motor made in 1995 and I have the leaky carbs... the leak is probably from the brass ball used to plug a construction hole....on the starboard carbs you can see the brass plug in the carb bowls.....hopefully when you get the new bowls they will already have the brass plugs installed...

I would definately clean the idle needle and orifice


bob

 

[captmello]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

Great help!! Thanks guys. Now to finish rounding up my parts. I'll update when I'm done. Soon I hope!!!

 

[jeffersondodson561]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

Make sure you verify the main jet correct size.

 

[Chris1956]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

Hey Jefferson, you got any analysis showing that today's gasoline starts to degrade after three weeks, or is that a guess? Same question about octane degradation.

I for one am skeptical...

 

[jeffersondodson561]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

Mercury Service Bulletin 93-3

 

[jeffersondodson561]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

Yamaha and Volvo have one as well, I wouldn't wouldn't post anything that is not true...

 

[Chris1956]

Re: '01 J90 60 deg 2 stroke Idle/low rpm

OK, Merc says 15 days before the start of degradation. OMC says guaranteed 3 month shelf life. Both are advertisements for a gasoline stabilizer.

15 days is a number that doesn't pass the "sniff" test (sic). I would think there is plenty of gasoline supplies that take longer than that from the completion of refining, until they are sold at the corner gas station. if not, we would not need tank farms to store gasoline.

I wonder if there is some non-advertisement info available.