getting lower unit off a johnson 8hp

sunbeam · Mar 25, 2004

getting lower unit off a johnson 8hp

I have removed the 3 screws, it wiggles but will not come off I have hit the cavitation plate hard using a piece of wood and a hammer, I am afraid I may bend or break it I have soaked it with liquid wrench stuff It is really stuck on there What can I do now????

Chinewalker · Mar 25, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

Hi Sunbeam, Not an uncommon problem with those 8hp models. Not sure why, but they are prone to having the driveshaft rusting into the crankshaft. Poor quality grease, or whatever, but the end result is that the driveshaft is more-or-less welded into the crank. I've found the easiest way is to first shim the lower unit off using wooden wedges. This will likely pull the driveshaft out of the lower unit, the waterpump drive pin may lightly damage the pump housing, but it's not a big deal. Next, remove the powerhead from the exhaust housing. and using a pair of vice-grips clamped on the shaft, tap it out of the powerhead. Penetrating oil may help a bit. Hopefully, the splines in the crank aren't rotted out and you can simply clean things up and reassemble. Be sure to use a good waterproof grease on those driveshaft splines when you put it back together! - Scott

sunbeam · Mar 25, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

You said to remove the powerhead from the exhaust housing?? That sounds simple buy looks difficult, how do I do that??? Using wood shims I force them between the upper and lower unit at the front and rear to force it down and pull the driveshaft off the water pump, and only minor damage will result

Chinewalker · Mar 25, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

Hi Sunbeam, Yep, that's what is SUPPOSED to happen, anyway. Go slow and easy and don't force anything. I would strongly recomend getting a manual for your motor - OEM is always best, but if not available try at the bottom of the iBoats pages - they sell some good aftermarket manuals... - Scott

sunbeam · Mar 26, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

I have tried driving wood shims in at the front and rear, but they just rip apart. What about using flat screwdriver blades as shims will they damage the housing There is little room at the front because the water pump unit is in there I have an Intertec manual but it does not discuss what to do if something is stuck or frozen what else can I try

rickdb1boat · Mar 26, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

Sunbeam I would not use the screwdriver method, as you may wind up cracking the case and then you would have a real problem. I would continue to do as the others have suggested with the wedges. Chinewalker deals with these older motors all the time and knows what he is talkin' about. It will come off eventually with enough persuasion. See if you can get ahold of a spray lubricant called PB Blaster and shoot it liberly wherever you can get it to. Let it sit overnight with the wedges in place and have at it again the next day.

Xcusme · Mar 26, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

Sunbeam, The idea here is to insert the wooden wedges,invert the motor,spray PB Blaster on the driveshaft. It should run down the driveshaft and soak the splines of the crankshaft. If you're lucky, it should loosen and serarate enough to disconnect the shift linkage remove the lower unit. Try putting in Forward or Reverse to get more seperation of the lower unit. As Chinewalker has stated, what may happen is, the driveshaft will pull out of the lower unit instead. The waterpump drive pin may catch on the water pump housing, it's no big deal. Disconnect the shift linkage and slide off the lower unit. This will leave you with the powerhead and exhaust leg, with the driveshaft and water tube sticking out. Remove the exhaust leg to powerhead bolts (6??), and slide off the exhaust leg. You should now be able to see where the driveshaft enters the crank shaft. I guessing that you'll find that some metal displacement has occured at the driveshaft/crankshaft junction, causing all this grief. Proper greasing of the driveshaft splines should have avoided this.

sunbeam · Mar 26, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

ok the engine model number is J8RCUD and I may be wrong because I am no expert, but I do not think there is a disconnect for the gear shift. I might be getting confused becuase I did not know that you could unbolt the exhaust leg from the powerhead, I thought that was how you remove the powerhead from the engine. All I see is 5 bolts holding the leg to the powerhead. If I take them out will the powerhead be loose on the rest of the engine? Wow and I though this was going to be a simple job just changing the impellor

Chinewalker · Mar 26, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

Hi Sunbeam, Whether you pull the powerhead free of the exhaust housing or remove the lower unit first, in either case you should be left with the driveshaft sticking out of the crankshaft. You are correct - there is no disconnect to worry about with that lower unit's shifting mechanism - it's a flat-sided rod seated in a coupling with a mating flat side. Hard wood wedges may work better, as they won't splinter under pressure. Screwdrivers will bugger up the mating surface between the lower unit and the exhaust housing. I am pretty sure there are six bolts holding the powerhead on - two rear, two on the sides, and two in the front. - Scott

Xcusme · Mar 26, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

Under normal conditions, when the lower unit drops a bit, you should see a gear shift rod connector. Remove one of the bolts of the connector and the lower unit would drop free. The lower unit will still have the drive shaft inserted. The drive shaft will go thru the water pump housing. So you should end up with a lower unit with driveshaft and water pump. This is the typical arrangement. Yours may be a bit different, but this is typical. As was mentioned earlier, if the driveshaft will not pull out of the crankshaft (frozen,rusted etc), the drive shaft should be able to pull out of the lower unit. It shouldn't be pinned or nutted in the lower unit. It should just pull out of the lower unit pinion gear. Naturally, the gear shift connector will have to be decoupled as before. When you go this route, the waterpump drive pin may narf the waterpump housing when you slide out the driveshaft. This still leaves you with the problem of the drive shaft stuck in the crankshaft end. This is when you would want to remove the exhaust housing bolts and remove the exhaust tube. This will fully expose the bottom of the powerhead and driveshaft/crankshaft junction. You can then liberally apply PB Blaster to the junction to work the driveshaft free. Clean up the splines of the driveshaft, inspect for damage. Clean out the crankshaft splines of all debris. On some driveshafts, there is a small groove just below the splines. This groove is for a small 'O-ring'. This o-ring helps to seal the splined end of the driveshaft and retain the grease. Upon reassembly, apply grease only to the splines themselves, not the very end of the driveshaft. Grease on the end of the driveshaft can 'per-load' the crankshaft, sometimes preventing full engagement of the driveshaft into the crankshaft. If the splines are not greased, metal displacement can occur and it can be difficult to separate the driveshaft from the crank (this is probably what you have now). The worse case scenario is that the crankshaft splines get sheared off. If this happens, the driveshaft won't be turned, and you're not going anywhere. The motor will run, but the driveshaft won't turn. If this did happen, there is a solution, but I'm getting way ahead of myself. As an aside, this is probably another good reason to change the waterpump impeller every couple of years. You get a good working waterpump and you grease the driveshaft/crankshaft splines too, which would help prevent the situation you're in right now. Keep us updated on your progress.

Chinewalker · Mar 26, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

There is NOT a shift rod disconnect on this motor! It is a flat-sided shift rod that slides into a coupling with a flat side to match. It's simple a slide-in/out deal. This motor does NOT use the old brass coupling with the two bolts... - Scott

Xcusme · Mar 26, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

Chinewalker, Thanks for the correction, you're right...after looking at the pics of my motor, it is a slip fit type fitting. Sorry for the dis-information.

sunbeam · Mar 27, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

You say to use hard wood wedges, where would one get such and item???? PB BLaster where do I get that stuff???

sunbeam · Mar 27, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

I have two wood wedges in there now and I can only get the parts seperated by about 1/8 inch. I am going to see if I can find this PB Blaster at the local auto parts stores

sunbeam · Mar 28, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

I found PB Blaster at NAPA auto parts I stood the motor on it's head and squirted it into the underwater exhaust port. I am hoping I got some on the driveshaft and that it runs down to the crankshaft to work on the rust in the splines. I let it sit overnight and will let it sit for another day or two. Is there anything ekse I can do if this does not work????

rickdb1boat · Mar 28, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

Spray it liberally every day, maybe twice, making sure it gets on that shaft. It will come loose in time. Can you shoot some into that 1/8" separation that you have?

sunbeam · Mar 28, 2004

Re: getting lower unit off a johnson 8hp

Re: getting lower unit off a johnson 8hp

I cannot see the driveshaft but I know about where it is, I will squirt that stuff in there again right now I hope this works I tried the using the wood wedges but it did not work, all that happened was the wedges broke apart as I tried to hammer them in place

getting lower unit off a johnson 8hp

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