94 mercury 90 hp reverse problems

[cozzmo1970]

yesterday as i was backing off my boat from the trailer a loud pop followed by clanging, now every time i put it in reverse it does the same. forward is fine. the throttle did stick once from reverse to neutral but now is fine. i was told the motor was rebuilt recently. the cables look original to the boat 1998 bass tracker. does anyone know how to properly adjust them, or how to determine the problem?

 

[jhow0228]

Re: 94 mercury 90 hp reverse problems

You may be looking at rebuilding the lower unit. Quite often when an outboard is rebuilt they only do the motor itself and not the lower unit.

 

[jhow0228]

Re: 94 mercury 90 hp reverse problems

It could have been the clutch dog too. Best advice, if you're not a mechanic, don't mess with it too much. Take it to one and let them diagnose the issue because it could be several things and one major headache if you're not experienced. You're looking at anything from replacing the control box and shift cables to busted gears in the lower unit.

 

[Texasmark]

Re: 94 mercury 90 hp reverse problems

The banging doesn't sound good. Reverse gear is a set of rectangular (square essentially) cogs and slots; cogs in the clutch dog (3 and in later model engines 6) and a corresponding number of slots in the face of the R gear. Unlike F, which has a built it overrun clutch and free wheels (clicks) in the overrun mode....turning prop cw looking from the rear, the cogs and slots lock and there is resistance in both directions.

Since Merc doubled the number I'd suspect that early on they failed frequently and you may have stripped either the dog as j said, or the gear. Since the gear is high tempered, I'd go with a stripped dog.

One thing about shifting that engine is that if running it's ok to shift from N to R at random. If it's not running you need someone to rotate the prop while you gently move the shifter into R until the cogs and slots line up. Then it will go ahead and shift. If you don't you can damage your shifter linkage.

If you have a manual, replacing the dog isn't that big of a deal, especially on the newer lower units where the prop shaft rear carrier bearing holder is held in with 2 bolts....reduces the effect of corrosion on getting it out of the LU.

There are no critical alignments in the process and the manual is quite clear. If you are mechanically inclined and can follow instructions you should be able to get it done. Pay attention to new LU oil and seals, the big oring on the carrier and the little fiber seals under the drain and (2) vent screws. The oil that comes out should not be muddy yellow or brown which indicates water intrusion and you have a leak that must be fixed along with your shift problem.

If Pennzoil it will be honey colored and Merc will be dark blue/black. The drain plug should contain a magnet to catch metal filings and a light coating with a few of them is normal. If you have blobs of metal on it then that is a good clue that you have torn up something. In your repair process ensure that you clean out the pieces that broke off. Use the premium Quicksilver/Merc oil in the Quart bottle with the pump. Makes refilling easy and no mess to speak of. Fill per instructions in the manual.

HTH,
Mark

 

[Texasmark]

Re: 94 mercury 90 hp reverse problems

The banging doesn't sound good. Reverse gear is a set of rectangular (square essentially) cogs and slots; cogs in the clutch dog (3 and in later model engines 6) and a corresponding number of slots in the face of the R gear. Unlike F, which has a built it overrun clutch and free wheels (clicks) in the overrun mode....turning prop cw looking from the rear, the cogs and slots lock and there is resistance in both directions.

Since Merc doubled the number I'd suspect that early on they failed frequently and you may have stripped either the dog as j said, or the gear. Since the gear is high tempered, I'd go with a stripped dog.

One thing about shifting that engine is that if running it's ok to shift from N to R at random. If it's not running you need someone to rotate the prop while you gently move the shifter into R until the cogs and slots line up. Then it will go ahead and shift. If you don't you can damage your shifter linkage.

If you have a manual, replacing the dog isn't that big of a deal, especially on the newer lower units where the prop shaft rear carrier bearing holder is held in with 2 bolts....reduces the effect of corrosion on getting it out of the LU.

There are no critical alignments in the process and the manual is quite clear. If you are mechanically inclined and can follow instructions you should be able to get it done. Pay attention to new LU oil and seals, the big oring on the carrier and the little fiber seals under the drain and (2) vent screws. The oil that comes out should not be muddy yellow or brown which indicates water intrusion and you have a leak that must be fixed along with your shift problem.

If Pennzoil it will be honey colored and Merc will be dark blue/black. The drain plug should contain a magnet to catch metal filings and a light coating with a few of them is normal. If you have blobs of metal on it then that is a good clue that you have torn up something. In your repair process ensure that you clean out the pieces that broke off. Use the premium Quicksilver/Merc oil in the Quart bottle with the pump. Makes refilling easy and no mess to speak of. Fill per instructions in the manual.

HTH,
Mark

 

[cozzmo1970]

Re: 94 mercury 90 hp reverse problems

thanks for the replies, i removed the prop then the housing to look at the dog clutch there was no metal at all and the cogs looked fine no scaring the lube also looked fine. i refilled the foot and adjusted the cable by placing the motor in reverse then adjusted the cable all the way back to line up. it now will go in to reverse but if i put too much power it "clangs" again. forward is fine. i suspect its the cable or dog clutch. im not sure what year the motor is i was told 1994 would the clutch dog and cables be universal? the vin is 0g152476. thanks again.

 

[Texasmark]

Re: 94 mercury 90 hp reverse problems

My thoughts. If you opened her up and found no damage, you aren't hurting anything. Like Merc says, the dog can rattle on some installations and don't worry about. The clean oil and no shavings on the magnets just sums it up. Go and have fun.

Mark

 

[carholme]

Re: 94 mercury 90 hp reverse problems

Your s/n comes up as:

MERCURY - ( 90 H.P. (1995 ))
Serial No: 0G152476 Model No: 1090412RD

Parts and Service bulletin list for s/n 0G152476:

Search Results - Crowley Marine

If you would like a copy of the service manual, PM me with an email address and I will forward a copy.

Gerry