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Author Topic:   Motor Problems - 2004 Mercury 90 HP 4S
Goosedog posted 04-19-2004 03:13 PM ET (US)   Profile for Goosedog  
This weekend I experienced the first hiccup with my 2004 Mercury 90 HP 4-stroke on a Montauk 170. After a good 30 minutes of use, I started in reverse and the motor started clunking (sounded similar to an out of balance washing machine). It wasn't the clunking associated with the heavier SS prop. Shifted to neutral then forward -- same sound. Turned motor off to see if anything was obstructing the prop -- it was clear. Restarted and in gear the clunking was gone. However, when I accelerated, the motor seemed to "skip" (pauses and reductions in RPMs). I got the boat up on plane, but it still felt sluggish. This skipping happened one more time when coming up on plane before we headed back in.

First, any thoughts on diagnosis? Second, I assume my dealer work would be covered by warranty (purchased new September '03)? Thanks in advance.

I'm not sure if this is the correct forum, but I'll gladly re-submit elsewhere if more appropriate. Thanks.

Peter posted 04-19-2004 06:14 PM ET (US)     Profile for Peter  Send Email to Peter     
Sounds like a gearcase problem. Could be misadjusted shifting mechanism allowing motor to slip in and out of gear or a bad gear. I seem to recall someone describing a gearcase problem with a Mercury 4 stroke on this forum within the last year.

A gear case problem will result in a skipping with a sound much like a blender grinding ice. The motor will generally convulse back and forth. At low engine speeds, the motor can be stalled if the gears get jambed.

Maximus posted 04-19-2004 08:34 PM ET (US)     Profile for Maximus  Send Email to Maximus     
No fuel injectors on this motor!!! The 90's are still carbed. If it is not a gearcase problem, sounds like you had a miss-fire. I would check plugs and wires.

How many hours on this motor?

Dick posted 04-19-2004 11:02 PM ET (US)     Profile for Dick  Send Email to Dick     
It's a 2004 motor and still under warranty, take it back to your dealer. Let them diagnose and correct the problem.


Goosedog posted 04-20-2004 09:34 AM ET (US)     Profile for Goosedog    
Thanks for the replies. It is at the dealer now for repair - but wanted to try to be somewhat informed before hearing back from them. The motor probably has 40-50 hrs on it. Thanks again.
ghefty posted 04-20-2004 09:45 AM ET (US)     Profile for ghefty  Send Email to ghefty     
Do you know if you hit anything, the skipping could be that you spun the hub in the prop. If that is the problem, it is minor and required the replacement of a $15 bushing. I know because I had a similar problem a couple of months ago.
Goosedog posted 04-20-2004 09:53 AM ET (US)     Profile for Goosedog    
It did not feel like I hit anything, but it is possible since I was in the shallows at the time. Thanks.
drewc posted 06-21-2004 07:38 PM ET (US)     Profile for drewc  Send Email to drewc     
Goosedog - did you ever resolve the problem? My brand new 90HP - 4 behaves mechanic suspects fuel starvation somehow, but the symptoms sound like what you are experiencing: shaking/convulsing at idle and then it dies. I'm curious to see if it turned out ot be mechanical (gear) or fuel issue. Thanks, Drew
jimh posted 06-21-2004 08:54 PM ET (US)     Profile for jimh  Send Email to jimh     
It is really nice when we get some feedback on the solution to problems brought up in articles like this. Perhaps we will hear of the outcome to this problem.
Clark Roberts posted 06-22-2004 07:04 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Once upon a time a thrust washer was not reinstalled when prop was changed and the symptoms you describe occured (sp?) as the prop chewed its way into the gearcase housing. Check it out! Happy Whalin'... Spruce Creek Navy
Goosedog posted 06-22-2004 12:59 PM ET (US)     Profile for Goosedog    
Sorry for the lack of response on the outcome, but I don't really have one. My dealer looked it over in the shop and couldn't determine a cause for the problem I described. The problem has not reoccured since being in the shop. I will let you know if it happens again and if cause is found. Thanks.

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