Transom bolt pattern for older (1983) 50HP 4 cyl Mercury with power tilt and trim

[sjpitts]

I know the newer Mercury outboards use the standard BIA pattern, but I am not sure what the older pattern is-- and in particular the pattern needed for the separate power tilt and trim.

The older mount has four mounting holes in a line that look to be narrower than the standard BIA pattern. I think they are about 8.75 inches apart in the horizontal. And it also has a clamp. But the power tilt and trim uses two additional brackets mounted on the outside that appear to require additional mounting holes farther out

The reason I ask is that I am considering trying to mount such an older Mercury 50hp with power tilt and trim to a hydraulic jack plate made for standard BIA pattern. I have seen examples where people have mounted the older Merc without power trim to such a jack plate.

I have attached a couple of pictures of a older 35hp Mercury with the old style power tilt and trim. And a picture I snagged from a video showing the mounting bracket. And a picture of the example I found where a person installed an older Merc on a jack plate-- but his example did not have the power trim.

It has occured to me that this may be stupid idea and I should just sell my older 50hp Merc and find a motor with the standard BIA pattern that mounts the power tilt and trim on the inside. But I am not there yet.

Thanks

 

[redneck joe]

I have an 82 50 on the boat in my driveway with same trim unit, tell me exactly what you want and I'll go get it.

 

[sjpitts]

I have an 82 50 on the boat in my driveway with same trim unit, tell me exactly what you want and I'll go get it.

I guess this distance between the hole on the trim unit bracket and the hole on the mount. But I am not really sure how it mounts.

Do you have two holes in your transom for each tilt bracket? One in the whole I highlighted and one in the slot below it?

To be honest, I am not even sure how this thing is really mounted. I cannot find any good pictures of a motor with the trim unit installed.

 

[BWR1953]

I had a 1985 Merc 50 4 cyl on my Kingfisher. I just held it in place over the transom with a shop crane (from HF) and started measuring to get center. Once I was absolutely sure I had it centered. I drilled the holes by using the mounting points as the drill guide. Easy peasy.

You might be able to do the same thing with your jack plate.

 

[Chris1956]

Your Merc and it's PTT system should use 6 3/8" bolts. One in each of the lower "arms" of the transom bracket and 2 on each PTT bracket. The bolt pattern is different from the BIA standard, but I was able to mount it to a Jackplate, with some new drilled holes. Remember, when trimmed, the PTT brackets take most of the thrust of the motor, so it needs those bolts.

Mark the bolt holes, punch 'em and drill 'em.

 

[jimmbo]

Old? That's an 84 or 85, I consider them Almost New.

 

[sjpitts]

Old? That's an 84 or 85, I consider them Almost New.

None of those pictures are actually my motors. I have two 50hp in my possession. One is still laying in the back of the SUV covered in grime and the other one is in pieces in the garage. When I get them out and cleaned up I will take some pictures.

I am hoping to get one functioning motor out the two of them. Only one has the factory power tilt and trim, and I wasn't going to use it originally because I also have this jack plate, but now I am not sure.

I really just bought them because they were cheap and I spent 20 years keeping an 84 caravell with a Mercruiser 140 stern drive running so I figured I had a chance to make these work.

My goal is to build a boat to up a particular river in Arizona I have wanted to go up since I was 12 years old. But I have never boated on a river and for that matter never boated with an outboard. So this is all new and I really have no clue what I am doing.

The serial numbers for my engines are 6420XXX and 6276XXX

I think that makes them both 83 models, but who knows.

 

[redneck joe]

Port side, motor down

 

[redneck joe]

Same, motor up. Two bolts

 

[redneck joe]

Bolts are approx 15" oc. I can get exact but i was in my pj's and it's kinda cold...

 

[sjpitts]

Bolts are approx 15" oc. I can get exact but i was in my pj's and it's kinda cold...

Thank you for your efforts in the cold.

The more I look into this the more I think I am going to have either not use the jack plate I have or not use the power tilt and trim.

Unless I were to not use either of these motors and instead find a newer one with a BIA pattern and the power tilt and trim between the BIA brackets.

The real problem is that my craigslist jack plate is not designed for this type of motor and mount.

 

[redneck joe]

What are you putting it on? Mine is an 18' aluminum center console and I absolutely love it. I sorta live without the trim now as my rams have a leak so doesn't always hole when up and running so I have a pin set second up from lowest and does fine. I run WOT at about 31 and im 220lbs. I cruise at 4000 rpm and that puts me at about 22mph.

Im new to merc but I have yet to hear anything bad about these 50s. With the trim the rams rebui.d kit is NLA but I found two on ebay for about 100 bucks each. When I do rebuild I'm going to match all orings and buy a bunch to resell. There is a brass part that I'll have the measurements to have fabbed if needed. That's my winter project.

Why jackplate?

 

[redneck joe]

I've seen where the 87ish tilt system can work on these but never dove deep into it.

 

[sjpitts]

So to start at the beginning, I have been wanting to go fishing at a place called Lee's Ferry in northern Arizona since I hiked in that area as a boy scout. It is the stretch of the Colorado River right below lake powell. You can put at Lee's Ferry and you can go up about 13 miles to the dam.

So one day last year I picked up a 1990's era V16 Lunker Limited. I bought this boat with the sole purpose of building it for Lee's Ferry.

The boat is a mess, and it has no engine. My original plan was to just put on a small outboard and go for it. But I asked around, and everyone said you can't get upriver with a small engine --- especially if you are filled with camping gear-- and I needed bigger.

There are also places where it can be shallow. So shallow that some guides run jet boats, but lots of people run regular outboards too.

So I have been reading and scrounging for parts-- and I picked up a 1983 50 HP 4 cylinder outboard that needed some work and some parts but I thought I could make it work.

But then I picked up an Atlas hydraulic jack plate off CL. That was really an impulse purchase because it was a good deal, but from what I read people said they were great to have on the river if you need to raise up the engine quickly. But I got it cheap enough that I am sure I could sell it for what I paid for it. Normally those things are crazy expensive.

And then I picked up another 1983 50 HP 4 cylinder-- and this one had power tilt and trim-- in addition to the parts I needed. And when I posted I was trying to figure out if I could make the Atlas work with this new engine and its power tilt and trim.

Now after looking at it all I don't think it would easy to mount the engine with power tilt and trim to the Atlas. In fact, I am not 100 percent sure it is going to be easy to mount these non BIA motors without the power tilt and trim to the Atlas.

So I am trying to figure out where to go from here. Do I try and fab something up to make it work. Or do I ditch the jack plate and install the engine with the power tilt and trim? Or do I use the jack plate and ditch the power tilt and trim. Or do a sell both motors and buy one with BIA mounting. Or try and convert one of these to BIA mounting.

I am also questioning my sanity.

Attached is a picture of my boat and picture of the same type of Atlas jack plate I have. Or at least similar to it.

 

[Chris1956]

If you plan on a trip up a shallow river, you will need a way to trim the motor. My Jackplate was a 2 piece kind. Basically on each side, there was 2 aluminum angle irons bolted together. A bolt on each allowed for up/down adjustment.

The width of the Jackplate allowed me to mount my '77 Merc IL6 PTT brackets and transom brackets on it. It was tight, but easily doable.

 

[redneck joe]

We are Boaters, we all question our sanity. The good news is as you get older we don't question it as much because we are old and we forget things...


I boat on a small lake here in TN and my favorite spot is to run up the main river feeder and go as far as I can. Some days depending on water level i get out and walk the boat in ankle deep water so I can run another half mile or so. Can't resist it, it's a draw and I've only seen another human that far up once and it was a family wading downstream from the road a mile farther up.

I budget a new prop every year, currently I'm using a solace 4 blade that runs about $150. Think I'll make it this year and not have to buy one, depending on how this week goes...

The trim works for what I need. Just go as slow as you can, trim as high as you need and as long as she's peeing keep going. My water gets really clear as it gets shallow. I do not run a depth finder.

My trim works well enough to not drop while doing this and I also keep close eye one it and bump as needed.

The 50 will be great on your boat imo. And you'll have a parts motor. I have an oem service manual i can share sections as needed.

 

[redneck joe]

This is the trim ram repair kit, currently 100 bucks on ebay.

mercury repair kit 64507a 1

Hoses readily available for about 35 bucks iirc and im hoping my pump is good it seems to be just a trim ram leakdown but new pumps avail.

 

[sjpitts]

This is the picture of the back of my jackplate-- where the motor mounts. You can see the BIA pattern holes drilled into the back plate.

The problem I am going to have is that the jack plate cylinders are about 16 inches apart-- meaning that they are going to interfere with the mounting of the brackets for the power tilt and trim.

The jack plate is itself plenty strong--it is made for bigger motors---
it is rated to 300HP and 600 lbs of engine-- so I could fab something up to push the motor back a bit and give room to mount the trim brackets, but at what cost?

So again I am left to choose between power tilt and trim or hydraulic jackplate plus manual tilt and trim.

At this point I am inclined to go with jackplate plus manual tilt and trim.

 

[Chris1956]

Gee, how about some 1 or 1.5 inch lumber spacers to allow clearance for the cylinders. S/b under $10 I would think.

 

[redneck joe]

Gee, how about some 1 or 1.5 inch lumber spacers to allow clearance for the cylinders. S/b under $10 I would think.

Or aluminum tube?