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Author Topic:   Mercury 90 Engines Idle Troubles??
The Chesapeake Explorer posted 11-30-2002 10:33 PM ET (US)   Profile for The Chesapeake Explorer   Send Email to The Chesapeake Explorer  
I am still researching my next engine for my 17ft Montauk. I like the 90 Yamaha but "gamesmanship" by dealers on service manuals and tools as posted on this site may make me change my mind. I have also considered the 90 Mercury carb motor. I asked a baot "wrench" about mercs and he said they were all good motors but had a idleing problem??? Any input on the Merc 90 carb motors?
JBCornwell posted 12-01-2002 12:10 AM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
Ahoy, Chessie.

My son's Montauk had a carbed Merc 90.

It was cranky about starting, smoky, noisy, thirsty and rough at idle and a transition point around 1200-1500rpm.

I think that nobody will be surprised that I recommend the Suzuki/Johnson EFI DF70 4 stroke for a Montauk. Mine would keep up with my son's Merc 90. It is a marriage made in heaven.

At least a half dozen of us here have that engine on our Montauks. I have heard no complaints, or even "yabut"s.

We sold the Merc powered Montauk and kept the older, Suzi powered boat.

Check for some excellent prices on off-lease DF70s.

Red sky at night. . .

JBCornwell posted 12-01-2002 12:13 AM ET (US)     Profile for JBCornwell  Send Email to JBCornwell     
The engine mentioned above was sold as an Evinrude before 2002.

Red sky at night. . .

Clark Roberts posted 12-01-2002 07:34 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Explorer, I have owned about 15 of these 3 cyl mercs (in 70-90hp versions in 71 and 85 cubic inch displacement) and have had absolutely no problems. Terrific performance and great fuel economy. On one engine (a 1995 ninety hp) I put 2170 hrs before selling and it's still going strong as far as I know. As for idling problems, I never had any but adjusted my own "idle/air" needle valves myself. Many others on this forum have this same engine and may have a different "take" on it. It is a very simple engine, easy to work on if needed and parts are readily available and reasonably priced but remember that anything mechanical can (and will at some time) break or need adjustment!!! To directly respond to your question... there are no "idling" problems that with which I'm aware. Happy Whalin'.. Clark... Spruce Creek Navy
Clark Roberts posted 12-01-2002 07:38 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
PS> Whoops, I did have stator problems on one of the 70hp and also on one of the 90's..(and of course, had to replace impellers, plugs and routine maint. items) memory is a blurr at times..zzzzzzzzz
mbking1 posted 12-01-2002 09:33 AM ET (US)     Profile for mbking1  Send Email to mbking1     
The Admiral has spoken...
newt posted 12-02-2002 12:49 PM ET (US)     Profile for newt  Send Email to newt     
I got about two solid months out of a '03 Merc 90 2s carb motor this year. I did not notice any idling problems, but the motor is brand new.

The only negative I did notice is that at a very slow idle, the resonance of the engine is well matched to my montauk's bow rail, and the clatter will drive you insane. I would consider that a bow rail problem, and not a motor issue though.

Good luck!

RWM posted 12-02-2002 09:03 PM ET (US)     Profile for RWM  Send Email to RWM     
I get a little vibe noise off the bow rail at idle with by 70 HP 4-stroke Evinzuki. Probably had the same thing with my 90 HP Merc but couldn't hear it :)
Dick posted 12-02-2002 09:33 PM ET (US)     Profile for Dick  Send Email to Dick     
Not a sound out of my Montauks bow rail with the Merc 50 4 stroke at idle.
Bigshot posted 12-03-2002 10:32 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
When the wind blows my bowrail vibrates. I can't keep it tight.....running out of toothpicks!
skred posted 12-03-2002 11:50 AM ET (US)     Profile for skred  Send Email to skred     
My merc 50 4-stroke idles fine until it's run for a while. Then, on startup, it's really rough, and even dies occasionally at idle. My dealer told me to increase the idle speed a little bit via the adjustment screw. Unfortunately, I did that adjustment while winterizing the motor, so I won't know if it worked until spring. I did shut down and start up a couple times during winterizing to see how it idled, and it seemed ok, but still a little rough. Dealer said to not touch the carbs' adjustments, however.
Dick posted 12-03-2002 03:22 PM ET (US)     Profile for Dick  Send Email to Dick     

I had an idle problem a couple years ago on mine. Took it in and found that the carbs were out of sync. Seems like no loc tite was used on the screws. Haven't had a problem since.

The Chesapeake Explorer posted 12-04-2002 09:39 PM ET (US)     Profile for The Chesapeake Explorer  Send Email to The Chesapeake Explorer     
Thanks for the replys ! Clark ..2100+ hours in 1995 Thats a whole lot of running! Good to know that outboards will go that long. I remember on my brocher on the 1988 Evinrude 90 that 2000 hrs on a outboard was the "life span" Mine still has a few miles to go with about 1600 hrs now but compression is getting low 115/115/105/99..As I have posted before the writing is on the wall for this motor but she may have to get me thru yet another year.
skred posted 12-05-2002 09:11 AM ET (US)     Profile for skred  Send Email to skred     

Thanks for the tip. This problem was evident even during break-in. I suspect the carb adjustments were off when it was installed, and they never re-adjusted 'em. I'm checking for loc-tite and seeing the dealer if there's none there...

Tin Man posted 12-08-2002 03:10 PM ET (US)     Profile for Tin Man  Send Email to Tin Man     
I ended up with the carbed Merc 90 JB was referring to. It had a loose vacum hose at one of the plastic fittings. I replaced the fitting with a brass fitting and replaced the wire ties with clamps. Cleaned the fuel system, carbs and changed out the plugs. Ran like a champ afterwards. Pretty good match for the Montauk although I took it off and placed it on another boat. I was looking to repower the Montauk with a fourstroke but ended up selling it sans the motor. I was looking at Yamaha F90 and the Suzuki 70 and had decided on the Yamaha because of the dealer and service options here. I heard from more than a couple people to stick with the Merc but was hellbent on a four stroke.

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