1972 Mercury 1400 lower unit and tilt/trim

[boatnut74]

I picked up a '72 1400 merc that has a cracked lower unit housing. It still goes in gear and sounds fine but the PO cobbled it together with JB weld. I was just curious what years are interchangable? Even if I find just a housing I can swap the guts over. A friend of mine has a 93 75hp with a blown powerhead, would this lower unit housing work? I'm sure they are different. His also has tilt and trim which I would really like. Is it compatable? If not what years would be.

[emckelvy]

Regarding lower units, any L/U from a '65-and-newer Inline Six will fit your '72 140HP. The one difference you're gonna find in later models is the lack of an O-ring groove in the driveshaft splined area where it engages & seals the crankshaft splines. If you need this groove for your motor and you find a later L/U that doesn't have one, you can grind the O-ring groove yourself.

Starting around '76 the driveshafts were stainless or stainless/clad in the wear areas so these are definitely more desireable than the older units with steel driveshafts, which were susceptible to corrosion in the oil seal area.

Note that 66 c.i. Inline Fours of similar vintage have the same style L/U. Later model 65HP's have 2.3:1 gears, as do all 75, 80, and 85 HP Fours, and '70-71 115's and 135's have 1.78:1 gears. These may not be an appropriate gear ratio for your 140, which came with a 2:1 gearbox. Not that they wouldn't work, but will definitely impact prop selection.

Inlines other than those mentioned have the 2:1 gears and it's easy to check, just count driveshaft revolutions for every one turn of the propshaft. You can do this in either Fwd or Reverse to check.

Other differences in design of the bearings and gears over the years make no difference in fitment, so what I'd suggest is find the best deal on the newest one you can get and let 'er rip! Lots of deals on Craigslist and you may luck out and find a whole parts motor on there for cheaper than you could buy a used L/U on eBay, for example.

lower units from the newer Big Threes and Big Fours are not compatible with the older Inline bolt pattern. So your friend's 75HP with the blown powerhead won't work.

From what I understand, the PT&T section may be possible to retrofit, but you'd have to swap out the entire steering yoke/transom mount assemblies, which would involve pulling the powerheads on both motors. The newer-style integrated PT&T units are real nice but you'd have to measure the mounting bolt spans (width of motor mount bolts top & bottom, and bolt spacing side-to-side) to see if they're the same. I've heard of this being done but haven't personally done it yet. I'd like to find one since I have a nice 1400 powerhead sitting on the bench to build. The integrated unit makes for a much cleaner installation, since you don't have any external hoses or pump to mess with.

Here's an older-style L/U which looks like it has the stainless-cladded driveshaft at the pump area:

http://www.ebay.com/itm/180777616163

Here's an example of a newer L/U that would retrofit to your 140:

http://www.ebay.com/itm/130618701777

Note the swept-back design, which was an upgrade from previous gear housings. '79-up were like this. I used a similar L/U on my beloved 1350 and it worked great (wish I had never sold it!).

Your 140 is more-or-less a 1350 with some tuning improvements on the exhaust side, a very fast motor on the right hull.

HTH & Have Fun!.............ed

[ThumbPkr]

Regarding Lower Units, any L/U from a '65-and-newer Inline Six will fit your '72 140HP. The one difference you're gonna find in later models is the lack of an O-ring groove in the driveshaft splined area where it engages & seals the crankshaft splines. If you need this groove for your motor and you find a later L/U that doesn't have one, you can grind the O-ring groove yourself.

Starting around '76 the driveshafts were stainless or stainless/clad in the wear areas so these are definitely more desireable than the older units with steel driveshafts, which were susceptible to corrosion in the oil seal area.

Note that 66 c.i. Inline Fours of similar vintage have the same style L/U. Later model 65HP's have 2.3:1 gears, as do all 75, 80, and 85 HP Fours, and '70-71 115's and 135's have 1.78:1 gears. These may not be an appropriate gear ratio for your 140, which came with a 2:1 gearbox. Not that they wouldn't work, but will definitely impact prop selection.

Inlines other than those mentioned have the 2:1 gears and it's easy to check, just count driveshaft revolutions for every one turn of the propshaft. You can do this in either Fwd or Reverse to check.

Other differences in design of the bearings and gears over the years make no difference in fitment, so what I'd suggest is find the best deal on the newest one you can get and let 'er rip! Lots of deals on Craigslist and you may luck out and find a whole parts motor on there for cheaper than you could buy a used L/U on eBay, for example.

Lower units from the newer Big Threes and Big Fours are not compatible with the older Inline bolt pattern. So your friend's 75HP with the blown powerhead won't work.

From what I understand, the PT&T section may be possible to retrofit, but you'd have to swap out the entire steering yoke/transom mount assemblies, which would involve pulling the powerheads on both motors. The newer-style integrated PT&T units are real nice but you'd have to measure the mounting bolt spans (width of motor mount bolts top & bottom, and bolt spacing side-to-side) to see if they're the same. I've heard of this being done but haven't personally done it yet. I'd like to find one since I have a nice 1400 powerhead sitting on the bench to build. The integrated unit makes for a much cleaner installation, since you don't have any external hoses or pump to mess with.

Here's an older-style L/U which looks like it has the stainless-cladded driveshaft at the pump area:

http://www.ebay.com/itm/180777616163

Here's an example of a newer L/U that would retrofit to your 140:

http://www.ebay.com/itm/130618701777

Note the swept-back design, which was an upgrade from previous gear housings. '79-up were like this. I used a similar L/U on my beloved 1350 and it worked great (wish I had never sold it!).

Your 140 is more-or-less a 1350 with some tuning improvements on the exhaust side, a very fast motor on the right hull.

HTH & Have Fun!.............ed

This should be made a sticky,it is very informative and addresses a very common question.Ron G

[boatnut74]

Thanks a bunch emckelvy! Great information. So, if I was to pick up a new lower unit off ebay which one of those would you recommend? It seems the newer ones housing is in better condition. Sometime next week I will go look at my friends motor and take some measurments to see if it might work.

[Texasmark]

This should be made a sticky,it is very informative and addresses a very common question.Ron G

Ditto

[boatnut74]

I found a '72 1150 Merc locally complete with tilt and trim and he says it runs. It is at a marina about an hour away. I remember seeing it on their website about a year and a half ago. They are wanting $995 but I would probably only give 5 or 600 for it.

[GA_Boater]

BN, is there a possibility that the crack can be welded? I don't know if it is a good idea or not.

[boatnut74]

BN, is there a possibility that the crack can be welded? I don't know if it is a good idea or not.

The crack was near the bottom right in front of the prop. Someone did a terrible job with jb weld and put a hose clamp around it to pull it all together. If it wasn't for that it probably would have been alright.

[GA_Boater]

The crack was near the bottom right in front of the prop. Someone did a terrible job with jb weld and put a hose clamp around it to pull it all together. If it wasn't for that it probably would have been alright.

Is oil leaking at the crack? If not, I'd take it to some welders with aluminum experience and see what they say about it. Asking them is free, so nothing to lose, BN.

[boatnut74]

Is oil leaking at the crack? If not, I'd take it to some welders with aluminum experience and see what they say about it. Asking them is free, so nothing to lose, BN.

I think it's leaking a little. The po put a hose clamp around it and covered it in JB weld. It looks horrible. I think I would just be better off finding a new (used) lower unit or a cheap parts motor that has a good lower and T&T. It would take a good bit of work to get the JB off.

[GA_Boater]

I think it's leaking a little. The po put a hose clamp around it and covered it in JB weld. It looks horrible. I think I would just be better off finding a new (used) lower unit or a cheap parts motor that has a good lower and T&T. It would take a good bit of work to get the JB off.

If it's leaking - not good to weld on it. You start getting the bearing and seal supports and things could warp and you will be worse off. I was just thinking that part of that area is basically partly an exhaust chamber leading to the prop. But leaks indicate it's into the gear housing itself - not good. Hope you can find something reasonable, but you don't a hove boat to put it on - YET.

[boatnut74]

If it's leaking - not good to weld on it. You start getting the bearing and seal supports and things could warp and you will be worse off. I was just thinking that part of that area is basically partly an exhaust chamber leading to the prop. But leaks indicate it's into the gear housing itself - not good. Hope you can find something reasonable, but you don't a hove boat to put it on - YET.

It was near where the propshaft seal would be. I also turned the prop by hand today and it doesn't turn true so i'm assuming the prop struck a rock or something. I might be on to a boat.....it's an IO but I think I could pull off an OB swap on it.

[boatnut74]

I got the motor pulled off and tested compression today. All cylinders were 95-102psi (with the exception of 6 because it's a bear to get to so I didn't try) I'm not sure what the original compression was but it seems good to me.

[GA_Boater]

I got the motor pulled off and tested compression today. All cylinders were 95-102psi (with the exception of 6 because it's a bear to get to so I didn't try) I'm not sure what the original compression was but it seems good to me.

All the inline Mercs are tough to get a comp. gauge in the bottom cylinder. Even my little 500 lower cowling blocks the plug hole. I finally borrowed a gauge from Autozone that I was able to use. Skipped the adapters and the hose end had the right thread for the plug. I still had to use some needle nose pliers to tighten, but it worked.

[capt jeff]

im trying to find out how to install lower unit on my 80 hp mercury motor (1972) have installed it twice and it is locked in forward gear no nuetral or reverse