Johnson 10 power head upgrade?

[willthur]

I have a nice 1961 Evinrude 5-1/2 that I put into good running order some time ago. Now, I find myself daydreaming about an OMC 10 hp, and style, my clear favorite would be the green 1955 Johnson QD-16. However, I know that there were some positive revisions to the 10 hp powerbeads for 1959 -63, principally needle bearings, thermostat, and fuel pump, and that these same later motors are sometimes available cheap with bottom gear case problems. So, the question is:

Will a ’59 – ’63 OMC 10 hp power head bolt into a ’55 Johnson 10 hp QD-16 ?

Problems I could imagine are the base gasket configuration, the recoil starter to case alignment, and carburetor knob alignments.

I’m hoping that someone with real experience with these motors can answer my question. Thanks !

[chris-p]

The short answer is no.

However, you can take take all the internals, and install them into your ’55

I have made quite a few of these upgrades now. You will need the pistons, connecting rods with bearings. The crank from your 55 can be kept.

You can also pull the bypass cover and fuel pump, and install it on your ’55

I have not figured out a way to get the thermostat on it yet though 🙂

[Anonymous]

What year were the wrist pins made stronger? 1961?

[chris-p]

yes the major change happened it ’61.

[willthur]

Thank you Chris P. for the helpful response. Very good of you to share your experience.

One more for you: I know this is silly, but possibly a better way to get the ’50s Johnson look with all the ’60s upgrades would be to start with a ’60 – ’63 10 hp Johnson or Evinrude, and fit it with the ’55 – ’58 Johnson die cast engine covers ? I don’t have a clear picture of how they bolt to the lower unit, so I don’t know if this is possible. One clue is that the change to the smaller lower unit happened in ’58, which still had the die cast covers, so maybe ’58 covers would fit up through ’63 ?

I realize that this would produce a big paint color mis-mash, so if it is possible, a complete re-painting may be part of the project.

Any advice ?

[chris-p]

If you want to upgrade your pre ’61 10hp powerhead, order the following:

Wrist Pin 307849 x2
Connecting Rod 378330 x2
Piston 378285 x2
Needle Bearing 378251×2
Big End Needles 378150 x2
Piston Rings 378416 x2
Circlips 302577 x 4

Then if you have her apart, might as well change the carbon seal o rings

301967 x2

[chris-p]

I cannot say for absolute certain, but I don’t think you could get the 50s clamshell hoods on a 60s leg. Not without major modification. Maybe someone will chime in for certain.

In my humble opinion, the best QD to build would be a ’57 (my favourite colour scheme, but any of the pre ’57s would work) due to the larger gearcase, then install the ’63 powerhead components in it.

I actually just finished one. Im just painting the cowl now and it is done. Ill post pics soon when the decals are on. It got the works, complete new powerhead internals, all new gaskets throughout whole motor, new ignition, carb cleaned and rebuild, new fuel lines, gearcase rebuilt and re sealed, all new water pump, full cosmetics, paint and decals and medallion, you name it I did it.

Guy came over last night to buy a motor from me and offered me 200 bucks for it. I politely declined. I have more than that into the powerhead in new parts.

ill admit, its not a real cheap thing to do, but if you have to open her up anyways to rebuild I would recommend it. The pre ’61 10hps had an issue with the wrist pin bushings wearing and causing slop. It can be tested by rotating the flywheel until the piston is on its down stroke, then push a punch or the like against the piston, and push in. If the bushing is worn, it will have some play. Ideally, it should have no play there.

[chinewalker]

The big hang-ups with the earlier cowling fitting a later powerhead concern the cylinder head. The 1959 & later heads do not have the cowling support ears cast into the side. I’ve never tried for fitment, but it’s possible the thermostat may be pretty close to the cowling, too. The earlier cylinder head will NOT fit a later block.

[willthur]

Thanks very much to Chris P. and Chinewalker for their helpful replies. – WillThur

[1946zephyr]

Yes, the ’57 and older, had the better lower unit. The smaller lower unit on the ’58 and later, was good too…..until water intrusion starts and neglect will shorten the life of it rather quickly. It’s basically an improved 5.5 lower unit, put on a 10. The old 5 bolt style lower unit was used on motors up to 25hp and 22 cubic inches, so the little ten horse power head was no where near a threat to it. I’ll happily sacrifice a couple extra pounds for lots more longevity.

As for the power head improvements, the points made here are correct. The wrist pins were a weak spot and did much better on the later parts.

If you’re pushing a 14 foot boat though, stepping up to a ’57 Fastwin 18 is a better choice yet. Much, much better motors

[Author]

Posts