POOR STARTING 90 HP MERC

[MD]

BEEN HAVING TROUBLE WITH MY 90 HP MERC (2 STROKE). EVER SINCE I BOUGHT THIS THING IT HAS NEVER STARTED OR IDLED WELL. THE MOTOR IS NOT EVEN 1 YEAR OLD YET, AND I THINK I'VE GIVEN IT ENOUGH TIME ON THE WATER TO BREAK ITSELF IN. I'VE TRIED ALL THE DIFFERENT STARTING TECHNIQUES THAT PEOPLE HAVE TOLD ME TO TRY, YET NOTHING SEEMS TO IMPROVE THE WAY THIS MOTOR STARTS OR IDLES OUT OF THE GATE. I'M REALLY SICK OF SCREWING AROUND AT THE LANDING WHILE OTHER BOATS ARE WAITING ON ME TO GET THE ##### OUT OF THE WAY!!! ANY IDEAS ?

[rock2me]

My brother-in-law got his Merc '00 90HP this year and ditto.

We have tried all sorts of things - choke, no choke, wiggle it, etc. with no luck. When we do get it running it runs rough for the first few minutes and sometimes dies. After it has run for awhile it is fine. Is this just a hard starting motor.

Anyone else have suggestions?

My '01 Johnson 90HP starts right up. Yeah!

[joe]

I owned one also, never again. Running from spot to spot they're fine but they idle rough and start terrible! My opinion is that the Merc 75 & 90 (same powerhead) are the poorest excuses for mid-range engines out there.

[CI_Guy]

LAST EDITED ON Sep-07-01 AT 10:38AM (CST)[p]Have you put new plugs in? New plugs make a huge difference in starting and idling with my 75hp mariner. Not sure how suface gap plugs work, but they seem to wear out gradually so you get used to the poor running characteristics instead of changing them right away.

[Mille Lacs Guy]

I also have a 90 horse Mercury-2 stroke, its a 99. The motor runs great, starts fine and idles fine. The dealer that I bought it from always re-adjusts the carbs when he gets the motors from the factory. He said one can run into the problems you guys are talking about by not having the carbs in tune. One problem I did run into with the motor is running fuel with ethanol in it. This motor seems to be more sensitive than others when running ethanol (it is tough to get gas without ethanol in it nowadays in most areas.) When I did run fuel with ethanol the motor did hardly want to run at all. I know a lot of people on this board, as well as other people that run 90 mercs and haven't had the troubles you are mentioning. I hope this helps.

Mille Lacs Guy

[miksup]

I would almost bet you haven't had it back to the dealer for the 20 hour check up and adjustment. I had a 1996 75. Same problem. Bought the service manual and found that Mercury sends these things out with the oil pump set rich to protect the engine in case some of us dummies don't use 50-1 oil ratio in addition to the oil injection during breakin. The adjustment is made on the arm coming from the carburators to the oil pump. It is a very easy adjustment. This is taken care of at the 20 hour check-up if you take it to the dealer. Of course I never took it in either. After I adjusted it the motor started much easier, smoked a lot less, and idled better. Also, after the warrantee was up, I tore it down and installed Boyesen dual stage reeds. The difference in starting and idling after that was like night and day.

[Dave in Mpls]

I, too, have a 90 Merc ('97, tiller) and have never had a problem starting it or getting it to idle smoothly. I take the thing out and troll for 10 hours at 800 RPM and she doesn't miss a beat. Some of the things I do include:

1. Run only premium non-oxy gas, even if it means driving out of my way to get it
2. Run 1 can of Sea-Foam for every 20 gallons fuel
3. Change plugs twice a season

Hope you find the cause soon. I know the frustration!!

Regards

[Box]

We had a 87 merc 90hp, 3 cyl. It ran great, but we did change the model of plug we used right from the start, at the suggestion of our mechanic. We ran a hotter plug and it ran much better, and kept running and starting great for 10 years.

We did have to choke the heck out of it the first time, and also if we trimmed it up to bass fish and the gas ran out of the carbs.

Also, try to make sure that when at idle speeds, the trim is all the down or gravity will act on the gas line. Ask bass boaters about this, they will tell you it makes a huge difference.

We also had a similar thing with our merc efi when we got it. It ended up being a kinked fuel line from the dealers "quick" setup... worth a check.

Good luck, and hopefully you find a quick easy and cheap solution!

box

[Tom P]

I bought my 94 90 Merc. in the crate and rigged it myself. I found that new motors was out of time by 4 deg. and the carbs were not syncronized. So much for final prep at the factory. They say the dealer would have done this if they would have rigged the boat. I will never know if that dealer would have gone through and checked it . It did not run the best, but kind'a ran like what you guys are talking about. You should bring it in or get a good factory manual and start wrenching. That motor ran and started very good for a 3 cyl.

[Leechboy]

I'm dissapointed in the performance of my 2000 90 hp Merc. Starts hard and is not smooth at low rpms. Use our kicker for most fishing applications now.-lw

[Paul H]

Starting - MAKE SURE IT IS LEVEL - yeah I'm shouting. There is no true choke it's enriched by an elec valve that dumps gas in it. At least mine does - a few years old.

If not level - it doesn't run in the carb.

[Scott]

I have a 99 75HP two stroke. It starts easily, idles smoothly. I've never had a problem starting it. It does load up if you idle a lot with the motor trimmed all the way down, but every carb engine I ever owned from 30HP to 225HP did that. Mine runs great.

[redbone]

MD. all motors are to be final run/inspected at the dealer before delivery. some need to be adjusted. all good marinas will do this. make sure yours did its part of the contract with the motor manufactures to sell there motors. all motors come with a predelivery inspection sheet in the crate just for this purpose.

have it adjusted and it should run fine.
good luck.
bob piette
npaa 859

[Larry M.]

MD
I to own a 00 9ohp merc and it runs great. I'm no mechanis but know that this particular model is a problem if Carb and oil injection is not set properly. Redbone and some earlier posts have it right - get it to a good mechanic. It's an excellent engine so don't give up.