Johnson J75TLCNB 1982 75 hp

[bill-loveland]

I’m talking to an ignorant seller of one of these beasts and haven’t any experience with them (the motor, not ignorant sellers). I may make the drive with a spare battery and jumper cables, a compression gauge and a set of lower unit muffs – other than checking the trim/tilt unit, gearshift and compression, what should I be looking out for?

And as far as checking the trim/tilt unit, gearshift and compression goes, is there anything there that I should be alert to?

[bobw]

I had one of those on my first boat years ago. Pretty good motor. Couple of issues you might want to look at:

Check trim/tilt unit seals for signs of leakage. Run trim/tilt all the way up and down thru a few cycles. When tilting the motor down, release the trim switch and let the motor stop about halfway down – if it keeps sinking down a few seconds after releasing the switch, the unit has air in the system which could indicate it’s low on fluid, maybe due to a seal leak.

With the motor tilted up, grab the lower unit and rock the engine up and down and side-to-side and see if there is excess play in the motor mounts.

The fuel lines had plastic tee fittings which were prone to breakdown/cracking from ethanol fuel. Check all the fuel line connections/fittings carefully.

I might pull the thermostat housing to see if gives any indication of corrosion/sediment in the cooling jackets.

Obviously, pull the gearcase oil drain plug to check for water.

Bob

1937 Champion D2C Deluxe Lite Twin
1954 Johnson CD-11
1957 Evinrude Fastwin 18
1958 Johnson QD-19
1958 Johnson FD-12
1959 Johnson QD-20

“Every 20 minute job is only a broken bolt away from a 3-day project.”
"Every time you remove a broken or seized bolt an angel gets his wings."

[bill-loveland]

Thanks Bob – I don’t usually think to pull the drain plug – if I’m getting a motor that uses oil in the LU, I’m usually getting it free or cheap.

eta: which reminds me – I have an awful lot of new motor acquisitions (including the free or cheap ones) that need to be gone through before winter. Damn. My to-do list just doubled.

[fleetwin]

Well, I am assuming this is a fresh water engine…If not, its value is less due to corroded fasteners etc.
The 75hp version of the 3 cylinder OMC is a bit more prone to detonation/preignition damage than its 70hp counterpart…So, bring your compression tester. Other than that, look for idle/sync adjustments that are way out of whack, this is usually an indication that someone has attempted to make a worn out powerhead idle acceptably. Idle quality is a pretty good indicator of powerhead condition on these engines, but only if run on a boat in the water…Running the engine on a flushette won’t tell much in its no load/back pressure condition. Look for signs of overheating also, try to determine why the seller is getting rid of what is usually a pretty decent engine. I would be interested in knowing what type/length boat the engine was used on and what size pitch prop was being used. Over propping these engines on larger non performance hulls is a pretty good way to damage the powerhead.
Other than looking for obvious physical damages to castings/gearcase, look to see if the engine still has its original powerhead, look for signs of being rebuilt also. The power trim units on these engines are pretty rugged, but look for obvious leaks like Bob suggested. You will need the power trim harness/junction box along with a control box for this engine, so be sure to get that from the seller.
Good luck, hope you get a good one for a reasonable price, how much does the seller want for the engine?

[bill-loveland]

Thanks guys – I’ve seen others in the area for less, but I wanted a 75. In fact, there’s a 65 with T/T about twenty miles from the 75 – if I can arrange it, I might try to take a peek at that one too.

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