Removing Lower Unit from 4-cyl 115 HP?

[kawiski]

2004 Mercury EFI 4-cyl 4-stroke 115 HP

OK, I posted the same question on Mercury technical section of this forum but very little response/help. So, here maybe some of Trophy owners with the same engine can help me out.

I am trying to remove the lower unit in order to replace the water pump impeller, but it won't separate from the midsection of the OB. I removed all 5 nuts (2 on each side & 1 on rear) just like the service manual says, but something else is holding it still tight. Manual doesn't say anything about unclipping the shift shaft end in the engine cowling area. Can someone tell me what I am missing?

 

[RWILLIAMS]

Re: Removing Lower Unit from 4-cyl 115 HP?

There is a bolt under the round (aprox 3 in) zinc anode under the caviataion plate. This plate can be either flat or have a small fin sticking down (this is used to help with the boat drifting under power).To get to it there is a black plug on top at the rear of the lower unit (back end of lower unit) You will need a 3/8 hex wrench to take the zinc plate off with. Then the bolt is accessed underneath (sp) were the zinc anode was at. I couldn't really tell from the pic if you had removed the zinc anode or not. Sometimes you may have to use a wedge on each side between the upper & lower case. Wooden wedges should be used to prevent damaging the mating surfaces if at all possible. Hope this helps.

 

[RWILLIAMS]

Re: Removing Lower Unit from 4-cyl 115 HP?

Looking at your pic again it looks like the 9/16 bolt on the top is what is holding the zinc anode on and needs to be removed. Also, the hydrofoil will most likely have to be removed (if it is a one piece hydrofoil) to get the zinc anode out. Then you should be able to get to the last bolt from underneath.

 

[kawiski]

Re: Removing Lower Unit from 4-cyl 115 HP?

Thanks for the reply.

I got some replys from the Mercury section but apparently there is no hidden nut under the anode trim tab on 4-st 115 HP O/B. However, yes, there is a hiddeen nut on other brand/model O/B though. The folks who were able to remove the loewr unit say that there are 5 nuts to remove, 2 on each side and one in the rear just front of the trim tab as I pointed in red arrow in the photo above. One owner wrote it took him several hours of pounding for the lower unit to drop down. Several hours?! I even called Mercury corporate office Customer Service and their tech told me the same thing. Just 5 nuts and it should drop down. I told them I did and about an hour of hammering that but still nothing happens. They said then "keep hammering" down on it. What?! Sounds like the hammer (or rubber mallete) is the required special tool for this job on Mercury O/B. I asked them why this is stuck so badly? Mercury says the drive shaft's splined end did not have enoug grease and it is probably corroded/stuck to the upper head area. Hmmm.... Mercury is the last one to assemeble that part (and didn't put enough grease) since the lower unit was never taken off before since purchased new. If so, shouldn't this be covered under the warranty?

Anyway mine is still stuck and it won't budge at all. I jsut don't feel comfortable about "keep hammering" idea but I guess it worked for other folks.

 

[TRUE GRIT]

Re: Removing Lower Unit from 4-cyl 115 HP?

well what was the problem?