Advice please re purchase of 1958 7.5hp Johnson

[2fast4me]

How bout that cork gasket and “O” ring for the lower crankshaft seal or am i thinking of the 5.5 HP. If present its a must replace item when doing the water pump. Someone correct me if I’m wrong, thanks Jim

2Fast4Me

[fleetwin]

Well, pulling the powerhead may indeed turn some folks “off”. But, I can honestly say that those powerheads usually come off easily (except if the screws are buggered/frozen from salt water). Trying to reinstall the gearcase on the later 6hp models can be very tricky, having to orient the roll pin along with water tube and shift connector….No way of knowing if you’ve done the job correctly once it is in place. Having to remove the powerhead makes it easy to inspect/service that lower seal assembly as well. OMC originally recommended 16:1 mixing, but lightened it up over the years due to oil improvements. Most here will agree that was a mistake on engineering’s part, perhaps the marketing department got in on the act, the same way that lead to the 100:1 disaster.
Let’s be clear, those older models with plain rod bearings should be mixed at 16:1, if you want to keep it from ventilating. The beauty of these old engines is that when in good shape and tuned correctly, they barely smoke at all (after initial start and warm up). All that being said, everyone is surely entitled to their opinions.
I will agree, that gearcase shock absorber was a case of “over engineering”, its failures far outweigh any benefits.
I don’t understand folks wanting to convert these engines to a fuel pump, provided you have a serviceable pressure tank. I suppose folks might want to be able to use just one style tank for all their engines, but then it would have to be mixed at 16:1 to run the older ones…

[Mumbles]

Your last year model ’58 7.5 does require 16:1 fuel mix. Nothing else. The ’61 – ’63 5.5’s with needle bearings on the rods big ends used 24:1 and starting in ’64 everything went to 50:1 except for the three horse JW motors.

[amuller]

Well, my CD 19 S (what does the S mean?) is a ’62. I’ve not had it apart but from looking at the parts breakdowns is appears to be a
plain bearing engine except for needles on the big ends. I’ve been running it at 24-1.

Now, the ’64 engine seems to be the same–plain bearings except for the big ends. So what makes this one OK at 50-1???? Are there other, non-obvious differences?

am

[Mumbles]

Oil meant for outboards was on the market in ’64. Before that 30W motor oil was the norm.

[amuller]

So it’s the oil that changed, not the motors, at least in this case?

[JOHN HOLBIK]

Back in the day we mixed all our outboards at 1 quart oil to a 5 gallon tank. Imperial gallons here in Canada .We had 5hp 5.5hp 10hp and 25hp all from the fifies.I still have the tn27 5hp it was the first new motor my dad bought in 1951.Most of these engines had thousands of hours on them.I believe most of the engine failures on the 5.5 and 7.5 were because there was no throttle stop in neutral I have heard many started at full blast and over rev while the inexperienced operator is trying to figure out what step is next.

[Monte NZ]

Thanks very much all of you for your replies……..much appreciated!……..you have certainly boosted my knowledge regarding 7.5hp models!!

Yesterday we went and had closer look at the motor and did a compression test. Top cylinder was 80psi and the bottom 70psi. Although the gauge is new, I can’t help wonder how accurate they are, even if brand new, but the fact that there was a difference of 10 psi between cylinders concerns me. There was spark on both cylinders which was a good sign. As there were time constraints regarding checking the motor any further, we didn’t get into draining and checking the gear box oil. The pressure fuel tank was missing, but I do have one with a 1957 Evinrude, but was considering converting to single line as my double line is perished and replacement line isn’t available here in NZ.

If I had time I would very much like to take it apart and restore to at least a reliable working motor, but unfortunately I’m heading for 79 and my wife is just out of hospital with a new hip, plus our daughter is currently having chemo after a breast cancer op. I was hoping that working on the motor from time to time would help take my mind off things a bit, but It looks to me to be requiring some major work and a lot of time to do the job properly, which wouldn’t be good at this stage, so I have decided to give it a miss.

However, all is not lost at this stage, as another member of our small group of AOMCI members here, could be interested and is going to check it out.

I think I will keep my eyes open for possibly a 1950s/1960s 3hp Evinrude/Johnson………will see what comes up.

Once again, thanks very much all of you for help!

Monte NZ

[fleetwin]

So, you bought the 7.5hp, correct? If so, recheck the compression. The gage may be inaccurate, but it does show a 10PSI difference which needs to be investigated. Does it show signs of being overheated? It sparks on both cylinders, so must have had ignition work at some point, so may have been run light on oil…. Have a look at the gear lube, then consider pulling the head/intake covers/perhaps the exhaust cover for a closer look….Skip the exhaust cover removal if the engine has been used in salt water, don’t want all the screws snapping off on you. Pull the powerhead for the water pump job, have a look at the lower seal pieces, could mean trouble if they are missing/mixed up….
Post some pictures if you can….D

[crosbyman]

http://www.youtube.com/watch?v=SVOedhzPP7M

dropping the lu

Joining AOMCI has priviledges 🙂

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