Changed Water Pump on Mercury 90 but Now Engine Lower Unit Always in Neatral

[kmk89]

I just replaced the water pump on my 1978 Mercury 90 (inline 6). When I put the lower unit back on, the gear control box is in neutral and the prop spins freely in both directions as it should. But, when I put the gear control box in forward (all the way) and the prop still spins freely in both directions. Same with the reverse. I pulled the lower unit off while the gear control box was in neutral, but I can't figure out how to get it to engage now that it's back together. Any ideas on where I went wrong and how I can get it to work?

 

[carholme]

Re: Changed Water Pump on Mercury 90 but Now Engine Lower Unit Always in Neatral

You haven't included your engine s/n but if you are sure it is a 1978, here is the parts list.

MERC 90 - Mercury, Mercruiser, Force, etc. Parts Lookup

Do you have PTT on your engine? If not,

Under GEAR HOUSING ASSEMBLY, COMPLETE (PAGE 1), see item 46 reverse lock cam. If you scroll down to item 46 and click on the picture, you will get a good view of it. Did you remove this cam off the lower shift shaft splines when you had the LU off? If so, it may be installed on the wrong spline.

Did you make sure that the boat controls were in the same gear as the LU when you installed it?

Here is a link to the condensed version of the Clymer manual. Download it soonest to your computer as the link is short lived.

MERCURY - MERCURY IN-LINE SIX-CYLINDER MODELS (1969-1988).: Small Engine Repair Reference Center Home

See Fig. M14-53 on page 316 to see the correct positioning of the cam on the shift shaft splines.

Gerry

 

[kmk89]

Re: Changed Water Pump on Mercury 90 but Now Engine Lower Unit Always in Neatral

The serial is 502XXX. I can't make out the last few numbers, but I know it's a 1978. Yes, the engine does have PPT. I took off the engine in neutral. My prop did spin a bit while I had the lower unit off. Is it possible that it misaligned the gear shifter thing in front of the water pump?

 

[carholme]

Re: Changed Water Pump on Mercury 90 but Now Engine Lower Unit Always in Neatral

Turning the prop shouldn't have altered the shift position but the shifter is very sensitive in neutral. Because the prop is freewheeling in all gears suggests that the LU (lower shift shaft) has rotated completely beyond the gear range. Best thing to do at this stage is drop the LU again and using a pair of pliers with a rag on the shift shaft splines, reset the LU. Take up all the loose play turning CCW until you come up against the first resistance and slightly beyond to engage what should be forward gear. Then, using finger pressure only check the prop to ensure what hear it is in.

Forward: Prop will ratchet when turned CW and will not turn CCW
Neutral: Prop will turn freely in either direction
Reverse: Prop will not turn in either direction

Then install the LU and check again for the same prop action as above.

Gerry