Pre Alpha Gimbal Housing (1971) replacement with Alpa One Gimbal Housing (1986)

[gerumpy]

Hi:

I would like to replace the current Mercruiser 1971 Gimbal Housing Assembly on my Aristocraft 19 (6 cylinder inline 165HP engine) with a newer version Alpha one Gimbal Housing Assembly (1986). I am assuming that I can use the existing transom plate that mates with the 6 cylinder engine with the new Gimbal Housing but not sure the bolt hole pattern is the same, or any other problems with that upgrade. I have not been able to locate a drawing that shows the dimensions of the transom mounting plate for the 1971 version, or for that matter, the 1986 version.

Would appreciate hearing from anyone that has performed this upgrade or that can direct me to some reference source before I engage in removing the engine and removing the old housing. I am looking at a 1986 used gimbal housing for a inline 4 engine, but the transom plate on that unit does not look like it would work with my 6 cylinder inline.

 

[Bondo]

Re: Pre Alpha Gimbal Housing (1971) replacement with Alpa One Gimbal Housing (1986)

Hi:

I would like to replace the current Mercruiser 1971 Gimbal Housing Assembly on my Aristocraft 19 (6 cylinder inline 165HP engine) with a newer version Alpha one Gimbal Housing Assembly (1986). I am assuming that I can use the existing transom plate that mates with the 6 cylinder engine with the new Gimbal Housing but not sure the bolt hole pattern is the same, or any other problems with that upgrade. I have not been able to locate a drawing that shows the dimensions of the transom mounting plate for the 1971 version, or for that matter, the 1986 version.

Would appreciate hearing from anyone that has performed this upgrade or that can direct me to some reference source before I engage in removing the engine and removing the old housing. I am looking at a 1986 used gimbal housing for a inline 4 engine, but the transom plate on that unit does not look like it would work with my 6 cylinder inline.

Ayuh,.... Welcome Aboard,... A '71 is pretty old, 'n I'm not sure,...
But, I'm reasonably sure that at worst, ya might need to open the holes slightly on yer inner plate to fit up to the Alpha 1 transom castin'...

The motor mount spacin', 'n the downpipe bolt up are different, for sure...
So you'll need the exhaust down pipe for the newer housin'...

 

[gerumpy]

Re: Pre Alpha Gimbal Housing (1971) replacement with Alpa One Gimbal Housing (1986)

Ayuh,.... Welcome Aboard,... A '71 is pretty old, 'n I'm not sure,...
But, I'm reasonably sure that at worst, ya might need to open the holes slightly on yer inner plate to fit up to the Alpha 1 transom castin'...

The motor mount spacin', 'n the downpipe bolt up are different, for sure...
So you'll need the exhaust down pipe for the newer housin'...

Thanks for the input... I noticed the down pipe on the inline 4 where the 86 housing is installed is different than the one on my inline 6 because the exhaust manifold riser goes sideways on the inline 4 and on mine the riser goes to the rear. So I was assuming that I could use my down pipe but if it does not mate with the newer housing, then that is going to be a problem. I haven't found any drawings yet that show the difference.

 

[Bondo]

Re: Pre Alpha Gimbal Housing (1971) replacement with Alpa One Gimbal Housing (1986)

Ayuh,.... That is 1 of the "Gotcha's",....

The angled riser from that 3.0l, Might possibly fit yer manifold...

 

[achris]

Re: Pre Alpha Gimbal Housing (1971) replacement with Alpa One Gimbal Housing (1986)

There's a lot of changes from your early MC-1 (NOT 'pre-Alpha'. I'm going to strangle the turkey that started that phrase if I ever find him ) to an Alpha One. It's unlikely the inner plate will fit the new outer, even if you do bore new holes in it. There are 2 hole I know are not the same, they need to come up about 1", and the sides need to be widened in the cutout.

As you have found out, the exhaust pipe doesn't fit, you'll also find out that the set up for the shift cable is different too. The old uses a 5-7/8" set up and the new uses a 6". I know that doesn't sound like much of a difference, but it is when the movement at the spool end is only about 1/2" each way. So you are going to need a shift plate from a later (Alpha One) engine.

Also the trim pump on the early system doesn't have internal reverse lock check valves, so you need to (somehow) set up the existing valve on the new shift plate, or get a new, later model trim pump.

The way around trying to use the old inner plate it to use the new inner plate, but then the rear engine mounts don't work anymore. The old mounting spacing was 14", the new is 10"....

Good luck, I think you are going to need it in spades. Trying to use old and new systems together is always a 'fun' experience. One usually avoided by anyone with any sort of experience with these things.

Chris......

 

[AviatorJim]

Re: Pre Alpha Gimbal Housing (1971) replacement with Alpa One Gimbal Housing (1986)

Yep, I have to go with achris. I started doing the same thing last winter. So I have an Alpha transoma assy, and inner plate. And then the flywheel cover doesn't match. I have a Alpha in my other boat so I thought I'd just swap some stuff. Long story is that going to the Alpha flywheel housing will work, but it moves the whole engine forward 2 inches. You can also go to the later cable layout on the manifold rather the the shift plate/trim lock, but that involve drilling the manifold, taps, heli coils.

Maybe worth doing if you wanted to go to a newer engine as well, but not to work with the chevy 250. You'd also need to go with the newer trim pump.

Lots of MC-1 transoms on Ebay in excellent condition. I bought two. Still have all that Alpha stuff too. Probably be 10 years before I need that.

--Jim

 

[gerumpy]

Re: Pre Alpha Gimbal Housing (1971) replacement with Alpa One Gimbal Housing (1986)

Yep, I have to go with achris. I started doing the same thing last winter. So I have an Alpha transoma assy, and inner plate. And then the flywheel cover doesn't match. I have a Alpha in my other boat so I thought I'd just swap some stuff. Long story is that going to the Alpha flywheel housing will work, but it moves the whole engine forward 2 inches. You can also go to the later cable layout on the manifold rather the the shift plate/trim lock, but that involve drilling the manifold, taps, heli coils.

Maybe worth doing if you wanted to go to a newer engine as well, but not to work with the chevy 250. You'd also need to go with the newer trim pump.

Lots of MC-1 transoms on Ebay in excellent condition. I bought two. Still have all that Alpha stuff too. Probably be 10 years before I need that.

--Jim

Thanks Jim and Chris. That pretty much clinches it. That represents too many changes..moving the engine forward is not an option as well as all the items mentioned. I will stay with the engine and gimbal housing as is. You all saved me a bunch of time and effort.

I will need to modify the gimbal housing for the new gimbal bearing somehow to accommodate greasing the bearing. The Alpha One housing has a zirc fitting outside on the lower starboard side of the housing, easily accessible for greasing the bearing at any time. I also need to provide some means to secure the hinge pins instead of the original aluminum nails which I had to drill out in order to remove the hinge pins. If I can resolve those two issues, I will proceed with the existing unit and will not need to pull the engine out.

 

[Bondo]

Re: Pre Alpha Gimbal Housing (1971) replacement with Alpa One Gimbal Housing (1986)

Thanks Jim and Chris. That pretty much clinches it. That represents too many changes..moving the engine forward is not an option as well as all the items mentioned. I will stay with the engine and gimbal housing as is. You all saved me a bunch of time and effort.

I will need to modify the gimbal housing for the new gimbal bearing somehow to accommodate greasing the bearing. The Alpha One housing has a zirc fitting outside on the lower starboard side of the housing, easily accessible for greasing the bearing at any time. I also need to provide some means to secure the hinge pins instead of the original aluminum nails which I had to drill out in order to remove the hinge pins. If I can resolve those two issues, I will proceed with the existing unit and will not need to pull the engine out.

Ayuh,.... Donno if it'll fit, but the newest gimbel bearings are Non-greaseable anyways...

'n,... aluminum welding rod/ filler metals come in various diameters,...
You could fashion yer own lockin' pins outa it...

 

[gerumpy]

Re: Pre Alpha Gimbal Housing (1971) replacement with Alpa One Gimbal Housing (1986)

Ayuh,.... Donno if it'll fit, but the newest gimbel bearings are Non-greaseable anyways...

'n,... aluminum welding rod/ filler metals come in various diameters,...
You could fashion yer own lockin' pins outa it...

Well now I am confused again! I was under the impression that the original gimbal bearing was a sealed bearing and therefore did not need any lubrication. The bearing was encased in a nylon housing, and the nylon housing was tightly fitted in the Gimbal Housing cavity with copper shims. That design is no longer available and the nylon housing has been replaced with an aluminum housing, which in turn is pressed fitted in the Gimbal Housing cavity. Instructions on the installation of the aluminum housing are that the grease hole in the aluminum housing for the bearing must line up with the grease hole in the Gimbal Housing cavity, which in turn is greased via a zirc fitting on the outside of the Gimbal Housing, starboard side. But my MC-1 housing does not have the hole in the cavity nor the zirc fitting, and so I read that the bearing has to be greased prior to installing it in the Gimbal Housing. Which I interpreted to mean that any other time the bearing is to be greased it will require removal of the stern drive and removal of the bearing! I did not see any reference to the replacement bearing being a sealed bearing as the original one. So now I am not sure which bearing I will be getting since I already ordered it, Sierra part number 18-2100.

I gave up with the idea of providing a means to lubricate the gimbal bearing with a zirc fitting on the outside of the Gimbal Housing after looking for a location for the grease hole in the cavity.

With regards to securing the hinge pins, I was not able to punch out the nails while attempting to remove the hinge pins. I gave up on trying to push them thru as the little head on the outside did not provide much room for grabbing it and pulling, even though I was able to straiten out the other end first. So in frustration I drilled out the pin on the port side pin, but I had to use a larger drill bit size than the nail because I found that the nail was much harder than the soft aluminum of the Gimbal Ring. Bottom line, the drilling was not very clean. I gave up drilling the nail on the starboard side and just drilled along both sides of the hinge pin in order to essentially "cut" the nail off right against the hinge pin. So I finally removed both hinge pins with the idea that I was going to replace the Gimbal housing with an Alpha One design unit since new MC-1 ones are no longer available. But now back to using what I have and today I managed to drill and tap with a 1/4 28 thread for using a 1/4 28 bolt in place of the nail, to be installed with anti seizing so that it can be released from the hinge pin if removal is necessary, and with a lock nut to keep it from coming out.

If it doesn't work out, I will be searching Craigs list and Ebay for a used MC-1 unit and end up having to pull the engine out after all!

 

[achris]

Re: Pre Alpha Gimbal Housing (1971) replacement with Alpa One Gimbal Housing (1986)

Well now I am confused again! .... Sierra part number 18-2100. ...

Welcome to the club. Your main text was completely correct. However, if you had ordered an OEM gimbal bearing you would receive a new 'sealed and greased for life' bearing. Just drive it in and forget about it.... Sierra are behind the times, by quite a few years...

Chris......