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  #1 (permalink)  
Old 08-10-2005
Matt
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All,

My 1988 90hp hasn't been idling well as of late and I'm definitely not getting all the top-end HP I'm used to. I believe my compression is OK and I don't think anything is wrong with my carbs...you never know, though, I suppose. Suspecting an ignition issue (problem is somewhat intermeittent), I went through my CLYMER manual and checked all the ignition components. All the stator pickups metered according to the book. But when I got down to metering the ignition coils themselves, all three secondaries checked out at 4,800 ohms, which according to my manual, is the reading for coils on a 70hp motor. The manual's stated resistance for 90hp coils is 2,500 ohms. So...can anyone confirm for me, possibly with different manual, which resistance I should be looking for? I wouldn't doubt it if my coils are wrong but I'd like to know for sure before I spend the $$$ to change them out. Any other wisdom on this issue would be appreciated as well.

Thanks in advance,
Matt
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  #2 (permalink)  
Old 08-12-2005
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1988 coils are 2500 ohms, 1990 are 4500 ohms.It's unlikely all 3 coils are bad. most of the time it is a carb problem
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  #3 (permalink)  
Old 08-12-2005
Ken
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Matt,
I would have to agree with boats.net mechanic that it is unlikely all three coils are bad.
If it has been at least three years since that 90 Yammie has been de-carbed, then I would do it.
Not only will this clean the pistons/rings of carbon but also will clean those carbs up a little, and maybe solve your rough idling.
If a decarb doesn't help the idling, then I would remove the carbs and do a teardown/cleaning and install a kit.
I would also advise you to get a Yamaha shop manual for that model outboard - it will pay for itself. Go to www.yamahapubs.com for online ordering.
Good luck,
Ken K
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Old 08-23-2005
Matt
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Ken & Boat.net mech,

After reviewing other posts with similar problems, I have to agree with you both that the coils are likely not the culprit. And I don't think my carbs have been touched in a long, long time, meaning a full rebuild is not out of the question. However, in the interest of squeaking out what little there is left of the boating season (in Maine), is the major carb cleaning you're refering to a SeaFoam treatment? I am unfamiliar with this product, what it might do for my problem, and where to get it, so any additional enlightenment would be a plus!

Thanks again,
Matt
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Old 08-23-2005
Ken
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Matt,
Seafoam is a strong detergent like Yamaha RingFree - when mixed with fuel and run thru the fuel system and power head, it dissolves gum, varnish, and carbon.
If you don't run a detergent all the time in your fuel, then gum/varnish/carbon builds up a lot faster, and you need to do a "shock treatment" on a regular basis. I do a shock treatment once a year, and I also run a 16 oz can of Seafoam to 16 gallons of fuel about every third 16 gallons. This schedule is what I use - everyone has their own idea about "how much and when" - Yamaha recommends you run their RingFree all the time - I personally think that is an overkill.
For now, doing a shock treatment with Seafoam on your 90 Yammie will (partially) clean the fuel system and pistons and rings. Seafoam, or any other detegent, is not a cure-all, in that if your carbs are gummed up bad enough [img]tongue.gif[/img] , a shock treatment will not fix the problem - try the shock treatment, and if that is not satisfactory, then a carb teardown/cleaning/rebuild is in order.
Go to my post dated May 27, 2005 to "CLL" where I describe the procedure - Seafoam is available at most major auto parts houses - I buy mine locally at Advance Auto.
Another thing you can do short of pulling the carbs and installing a carb kit, is to pull the jets of the carbs and squirt Berryman's Chemtool into the orifices - check the Yamaha manual for the location of the jets - there are pilot jets for low speed and main jets for high speed. Not all of the jets are accessable w/o removal of the carbs.
Good luck, and let us know how you come out [img]smile.gif[/img] ,
Ken K
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Old 08-25-2005
Matt
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Ken,

Thanks for the advice. Advance Auto Parts is just up the road, so I'll swing by after work to see if they stock Seafoam. As you suggested, I'll give it a shot and follow-up with a carb overhaul only if necessary. I'd rather do that this winter, anyway!!! Just in case, though, I've heard that the Yammie carb kit contains parts for all three carbs, but I'm not sure???

Thanks again and I'll let you know how everything pans out.

Matt
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  #7 (permalink)  
Old 08-25-2005
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includes all 3 but generally only worn parts need to be replaced.
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  #8 (permalink)  
Old 08-25-2005
Terry
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Please share your results. I also have a 1988 90HP that's due for a refresh. I have the parts, but not the time. I had idle problems and still have lack of top-end power.

For the idle issue, I found that the butterflies of the individual carbs were not lined up with each other. Center carb was opened up to the end of the idle speed adjuster screw and the upper/lower carbs were pretty much closed. If you need to make this adjustment, be aware that the upper & lower carb butterfly linkages are held by a left-hand thread screw. (turn right to loosen.)

1) Loosen the idle stop screw far enough to fully close the center carb butterfly.
2) Disconnect the link from the ignition advance arm to the throttle cam. (the one that controls the carb butterflies.)
3) Loosen the upper & lower butterfly setscrews (LH thread).
4) Ensure that all 3 butterflies are hard closed.
5) Retighten the upper and lower butterfly setscrews.
6) Set idle stop adjuster screw to slightly open the butterflies.
7) Start engine (on earmuffs & hose) and set idle to ~800 rpm using the idle stop screw. Stop engine.
8) Push the throttle roller against the throttle cam.
9) Adjust throttle link ball joints so that they line up over the pins, tighten counter-nut and reconnect the link.

If you have a SELOC manual, it does a VERY good job detailing things to do with this outboard. I have both the Yammie and SELOC manuals--the SELOC is by far and away much better for the home mechanic.
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  #9 (permalink)  
Old 08-26-2005
Ken
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Terry,
Good post [img]smile.gif[/img] - thanks!
Dang, if the Seloc manual is THAT detailed, I think I will get one to go with my Yamaha manual .
Ken K
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  #10 (permalink)  
Old 08-26-2005
Matt
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Terry,

Thanks for the detailed procedure. My carb adjustments have not been touched in probably years and the visible mechanical movements look normal. However, I have seen droplets from the jets while running, which is what I think is probably causing the majority of my problems,i.e. poor fuel atomization, fouled plugs, poor idle & lack of top end performance. We'll see, though. I'm going to shock the system and follow up with a rebuild, if necessary.

Oh, and finding the time is huge problem for me too!

Thanks again,
Matt
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