1982 150 V-6 lower unit interchange

[rla0248]

I may be looking for a used lower unit for a 1982 150hp V-6 mercury.<br /><br />What years will interchange?

 

[danvillemarine]

Re: 1982 150 V-6 lower unit interchange

It appears that a 1976-1985 will interchange. Try obrparts.com for reference.

 

[rla0248]

Re: 1982 150 V-6 lower unit interchange

Thanks AAA,<br /><br />Does anyone know what the difference in the early model (76 - 85) and the newer model lower units is?<br /><br />There's a guy with a 1998 lower unit on ebay that I have emailed. He says that his 1998 will fit all V-6 models from 2005 and older.

 

[phatmanmike]

Re: 1982 150 V-6 lower unit interchange

all of the 2.0 2.4 and 2.5 motors interchange. im honestly not sure about the 3.0L motors. ive never owned one.<br /><br />the difference you ask would be the gear ratio and type of driveshaft. preload or standard

 

[BF]

Re: 1982 150 V-6 lower unit interchange

I'm pretty sure that the driveshafts are different between your 82, and the later ones. IIRC, 82's have the pre-load pin on top of the driveshaft (and a thinner driveshaft), while later ones (84+ ??) don't use the preload pin... <br /><br />I went through this with my lower unit a couple years back when it twisted the drive shaft. I ended up getting a used shaft from a small outboard shop, getting new bearings etc, and re-doing it myself. Still going strong, and at ~$600 total was cheaper than getting another unit (which was impossible to find locally anyway).

 

[rla0248]

Re: 1982 150 V-6 lower unit interchange

Thanks,<br />I'm not sure what the preload pin is. Do the driveshaft splines slide directly into splines in the crankshaft? I had the lower unit off to replace the water pump recently and I don't remember anything at the top of the driveshaft, except for the splines that mate to the crank.

 

[roger3645]

Re: 1982 150 V-6 lower unit interchange

r_l_ Are you considering an LU because you are getting water in the LU? (Read your previous post). If so the LU leak is fixable without buying another LU. What is the condition of your driveshaft were the water pump base seal rides the driveshaft if it is pitted or has a groove in it then thats were the leak is. A pressure check with the LU off and under water may help to show were the leak is. The escaping air bubbles will point to the leak.

 

[BF]

Re: 1982 150 V-6 lower unit interchange

the preload pin is a little pin that sits in a hole in the center on the very top of the driveshaft. IIRC it is spring loaded, so when the LU is installed, it puts downward pressure on the driveshaft. I don't recall if is the bearings, or the mating of the pinion and forward gears that is designed to have this downward force for these particular LU's. The bearings I'd guess.<br /><br />The seloc manual has pict's of both types of LU's and also explains how to properly shim the driveshaft for the 2 types of LU's.<br /><br />Ditto that you might consider fixing your LU rather than buying a used one (which could have it's own problems)... If it is just a water leak, you should find it and fix it! (and consider yourself lucky)<br /><br />Even if you do buy another, your old one is probably worth more than you expect if the gears are good and driveshaft OK. Those parts are pricey.... Even the empty casings are sometimes sought after (people crack 'em on rocks, but their own internals may be OK)<br /><br />There was a used V6 LU that pressure tested OK around here... not rebuilt or anything, not even a new water pump... they were asking $1500 firm. It turned out to be the wrong one for me anyway. That's when I decided to take mine apart to really see what was wrong with it (had nothing to lose). I'm glad I did.<br /><br />good luck.

 

[rla0248]

Re: 1982 150 V-6 lower unit interchange

I will be trying to correct the leak, but I saw nothing wrong with the driveshaft surface where the water pump seals ride. Clean with no grooves.<br /><br />I'm wondering if it is possible that the housing is cracked internally, allowing water and oil to mix. <br /><br />I'll try to pressure check it. I don't have anything to submerge the lower unit into. What do people use for this purpose? Home Depot should have a plastic container big enough, I guess.

 

[roger3645]

Re: 1982 150 V-6 lower unit interchange

Okay if you have a good seal around the driveshaft, then the next and cheapest seal to check is the seal around the oil drain/fill screw and vent screw they should have some type of water sealing washer around them. Do you have a plastic garbage can that'll hold water?

 

[BF]

Re: 1982 150 V-6 lower unit interchange

go to wally world and treat yourself to a $7 kiddie pool. Rig up a way to pressurize it a little... You can improvize something... I've used a rubber stopper, small tubing and a syringe... you can use a bicycle pump and an old valve stem (trim it down and jam it into the fill/drain hole), or use the screw-in fitting for one of the little oil fill pumps for changing the LU oil. If you don't have one of those, pick one up at wally world while you're in there. They're dang handy.<br /><br />You just need a little air, do not exceed 10 psi or you will blow out good seals. With a leak it won't hold air anyway, you just want to be able to lay it in water and see where bubbles come from when you put some air in. The few times I've done this on my motors, the leak was obvious.<br /><br />Yes, the little seals around the drain and vent screws can be a problem... also the seal under the water pump can wear out, even if the driveshaft isn't grooved. Could also be a prop shaft seal. They can be damaged when fishing line is caught up in the prop. It's much more likely to be a bad seal somewhere than cracked casing. It that were the case, you'd probably be dripping oil out it.<br /><br />Aside from water getting in, does the unit work OK?<br /><br />Also, treat yourself to a manual... sometimes a picture is really helpful.<br /><br />good luck!

 

[roger3645]

Re: 1982 150 V-6 lower unit interchange

My guess would be the seal around the driveshaft on the waterpump base.

 

[rla0248]

Re: 1982 150 V-6 lower unit interchange

Other than water leaking into the oil, the lower unit seems to be OK. I just bought this boat and motor. I basically paid for the boat hull only. I knew the motor had a few issues and because of its age was not worth much.<br /><br />Because of the water in the oil, I have not used the motor much. Went fishing for a few hours. Mostly just idled to areas close to the launch ramp. It shifts into forward and reverse normally and I can't hear any strange noises, so I guess it might not be damaged. But I have no idea how long the previous owner used it with water in the lower unit.<br /><br />When I put the new water pump base on, I lubed the seals with lower unit oil before sliding it dowm. Let me know if I should have done something else.<br /><br />I will take the unit off this weekend and see what I can find out.<br /><br />When I pressure test it, if the water pump seals are the problem, where will the air escape? At the top of the water pump, where the driveshaft goes into it?

 

[roger3645]

Re: 1982 150 V-6 lower unit interchange

Okay since you replaced the water pump base and new seal you may be good there. Did you replace the water pump body gaskets as well? The bubbles will come out around the water pump or driveshaft if leaking from the pump. Others areas will be prop shaft, shift shaft, fill/vent screw area. The complete seal kit prob runs about $75.00. Good Luck! You'd be suprised how much a good running 150 is worth.

 

[rla0248]

Re: 1982 150 V-6 lower unit interchange

I removed the lower unit again and pressure tested it. The only escaping air bubbles were around the vent plug. I'll describe what I did, let me know if I should have done something differently.<br /><br />I put the hose from a lower unit pump/fill thing that I bought at West Marine into the fill hole at the bottom. I put about 10 psi air pressure to the hose for about a minute. The lower unit was submerged up to the top of the water pump. The only air bubbles were from the vent plug, and with a new gasket. <br /><br />I can't see any damage to the lower unit case or plug that would cause a bad seal at the area. I bought the new gasket seals at West Marine. They appear to be slightly to large of a diameter and after a day in the water seemed soft like it had become soaked with water.<br /><br />Last week I tried to order the seals from iboats.com, but according to their website they can not ship mercury/quicksilver parts to California.

 

[rla0248]

Re: 1982 150 V-6 lower unit interchange

While carrying the lower unit I noticed that the driveshft moves up and down a little bit in the case. About 1/2 or 3/4 of an inch. Is that normal?<br /><br />I got Mercury seals and tried the pressure test again, with the same results. If I tighten the seal normally, I get quite a bit of leak. If I tighten the sh.t out of it, the leak slows. I believe that the threads in the case have been cross-threated and the plug is going in at an angle. Is there any way to repair those threads. Thanks.

 

[rla0248]

Re: 1982 150 V-6 lower unit interchange

The vent plug threads were cross-threaded. I have repaired the threads as best as I could. Now no leaks on pressure test.<br /><br />If I pull or push on the driveshaft it will move up and down about 3/8 inch. Is this normal?