Re: Buying advice needed 1972 Evin. 100HP
These motors can either be great motors or money pits. Its all in the condition and the care that they received during previous ownership. I own a 1972 Johnson 65hp motor (3 cylinder) and love it. I paid $400 for it and put about another $1,600, including a steering adapter, into it. The first bit of refurbishment was done by an OMC/BRP dealer, who charged me $70/hr, plus BRP parts prices, so The $1,600 total refurbishment cost is not representative of the cost to upgrade the engine by someone who has the ability/time to do the work themselves. When I finished the job by rebuilding the ignition system myself, with aftermarket parts, my cost was about a third to a half what it would have been at the dealer.
Other than general mechanical health, the two biggest concerns with the motor that you are looking at, is the shift system and the ignition system. My personal opinion is that the ignition system on "yours" (different than on the 65hp model) is the bigger problem.
The hydro-electric shift system uses electrical solenoids (not electronic) to move a pair of poppet valves in the gearbox. The reason why the motor will not shift unless the motor is at least cranking, is because those poppet valves merely open or close a pair of hydraulic paths, which allow fluid pressure to move a piston, which in turn, moves the clutch dog. As has been mentioned, the motor defaults to the forward position. The reason why this is true, is because the piston is spring loaded to the forward position. Engagement of one solenoid moves the piston back one step (neutral) and engagement of the second solenoid in concert with the first one, moves the piston back another step (reverse).
As F_R pointed out, knowing whether or not water intrusion into the gear box has taken place, is crucial in the buy/no buy decision. Generally speaking, the solenoids tend to stay in good shape, unless water intrusion has occurred. If it has occurred, buying the motor is a gamble, because the lower solenoids are now an NLA part. You might be able to find a used one, but used parts are always a gamble, in their own right.
Next on the list is the wiring assembly that runs down the midsection. There isn't really anything complicated about this part, but they are NLA items and the key feature is that they consist of a pair of wires encased in a rubber shell. That shell, which both protects the wires and forms sealing points on the ends, is subject to becoming brittle over time and is often damaged during water pump servicing. In particular, if the gearcase is allowed to freefall before the wires are disconnected, the wires often break.
The shift circuitry between the midsection and the control unit is certainly important, but is much easier to fix, if there are problems. Its once you get to the control box that things get to be a concern, once again. In both the ERude and Johnson units, there is a switch assembly that tends to go bad. The Johnson switch is a toggle switch that is actuated by moving the single lever. That switch is a dealer direct item and is very hard to find. The Erude switch is a "three button switch" and is listed as being available, but no price is given. The bottom line is that, even if you can find what you need for your particular control unit, its going to cost you dearly.
The ignition system in the motor that you are considering, is a battery CD system, which is different than the magneto CD system that I have. My motor has a stator, timer base and powerpack, while yours has a distributor system and a pulse pack. The problem here is that the distributor is hard to find and, depending on who you talk to, the rotor is either extremely hard to find or is NLA. The pulse pack is available, but currently lists for about $480! On my motor, I was able to use CDI and Sierra parts to rebuild the ignition, at about half the cost of the BRP parts. I don't know for sure, if either of these companies makes the parts that you would possibly need, but I don't think they do.
My take on your potential purchase, is that you ought to insist on trying to test the motor. Trying to get it in a barrel might be hard, but you can at least do a compression check and test the igntion by using an inductive timing light on the high tension leads, to see if all four cylinders are likely to develop adequate power. You can also hook up the control unit and run the motor on a stand, with a hose/muffs hooked up. I've done this with a second '72 J65 that I own. What I would do is to build it advance (it doesn't cost much) and bring it to the motor with a buddy to help you mount it. See the photo below, for an example.
All of this said, if your can get the motor for $200 or less, buying it isn't a huge gamble. You could easily part it out on EBay and get your money back, plus a bit. The motor in my photo was purchsed for $150, because the shift switch was bad. I tend to buy stuff as I see it, whether I currently need the part or not, so I had a replacement and now have another usable motor ... well, at least after I rebuild the carbs on it!
Good luck with your purchase ... I hope all of this helped!
PS: The Johnson control unit has a warm up lever, because the single handle can not be moved forward without both interrupting the start circuit and putting the motor in gear. I just looked at the ERude parts diagram and don't see a warm up lever. I would guess that is true becaise the neutral protection circuit and shift circuits are built into the push buttom assembly, allowing the throttle lever to "opened" a bit during startup.
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