2007 Mercury 90 elpto not running well

[albow77]

I just bought my 07 crestliner fishhawk with the 90hp elpto merc 2-stroke. It had about 5 gals of old gas and I topped off the tank with prem. I got it on the water for the first time and it idled great for about 2 mins. After that it seemed to drop off to 2 cylinders. We were going to load it back onto the trailer and work on it but I found that if I slowly increase the throttle it will come off idle and fire on all three cylinders. If I go from idle to WOT quick it will stay on 2 cylinders. If I make a long trip and the motor is running great at higher rpms but if I bring it back to idle it will run on 2 cylinders again. When the trip was over I changed the plugs and they looked new but the top 2 cylinders had lots of oil on the plugs. The bottom plug looked like it was the only one that was firing on and it had a nice cardboard brown color. I have new plugs in and added Sea Foam to the tank for a start. I have read a lot about these 90hp mercs and found that they don't like to idle well. My question is should I pull the carbs and clean them or should I mess with the air/fuel screw to lean the top two cylinders out. Also what is the setting for a starting point on the screws like all the way in and back out 1-1/2 turns.

I have worked on snowmobiles for years so is there any difference in taking off the carbs and cleaning them?? I know everone says they need to be in sync but how hard is that to do.

Any input will help.

Thanks

Chad

[Burr]

Have you ran it since you replaced the plugs? That model year Merc 4 strokes would go through plugs, run really terrible, and new plugs would do wonders for them.

You may have taken care of the issue with the new plugs.

[Box]

FWIW, we had an 87 merc 90 (3 cyl. 2 stroke) that I think was the same motor. Our mechanic had us change from the noted plugs to slightly hotter plugs and once we did that the motor ran flawlessly the next 10 years. Not sure if that is still the case or maybe that is the plug to use, or they changed specs. If I recall... waaaay back though, the plugs were something like BU8H BUH8 or something like that.

We trolled a ton, and it idled fine, went slow (2.5) and when it would start to load up we just went for a short ride and then back to trolled after we fogged for skeeters

Good luck.

[albow77]

I will take it out in the morning. 2 cans of seafoam and new plugs. I also found a buddy with the same motor and he has a service manual for it. I will let you know how it runs and how many fish were cought.

Thanks.

[ryan1234]

Hi Chad, I have the same engine with the same trouble. The engine you have is made to run on two cylinders to save gas.. also I would not touch the setting on the carbs bring it to a good mechanic you will screw them up. Maybe you should fish from shore for a while.

[Indybleck]

I had a 03 125 that had the 2+2 system, I never had a problem trolling or getting it back up to full speed. The only thing was if you wanted to do a hole shot there would be a little hesitation before it really got going. I owned that boat for 3 years and never changed the plugs, and I trolled a lot they just never fouled out. That was a strong runner.

[wallymn99]

i am surprised anyone ever got a ELPTO running well. I have a 50 on my pontoon, hate it, worst motor ever. never has run right and it's brand new. I guess they require a good mechanic to tune it correctly.

[Jester1797]

I had the same problem on a 1994 50 HP ELPTO.....ran well up to about 1/3 throttle then coughed and chugged. Ran it to the marina, they changed the plugs, and she ran like like a quartz clock thereafter.

The plugs are a good place to start.

[Ristorapper]

Originally Posted by wallymn99

i am surprised anyone ever got a ELPTO running well. I have a 50 on my pontoon, hate it, worst motor ever. never has run right and it's brand new. I guess they require a good mechanic to tune it correctly.

once tuned correctly I wouldn't trade it for the world; bulletproof!!

[Esoxchaser]

Originally Posted by wallymn99

i am surprised anyone ever got a ELPTO running well. I have a 50 on my pontoon, hate it, worst motor ever. never has run right and it's brand new. I guess they require a good mechanic to tune it correctly.

I had a 90 that was the best black motor I ever had, never needed anything in the ten years I owned it but fuel, oil, plugs and Seafoam. Had a zillion hours on it when I sold it, and it is still going strong. . Much more reliable than my Optipop.