Topic: Comparing ’62 with ’73 Fisherman – Antique Outboard Motor Club,Inc

This topic has 11 replies, 5 voices, and was last updated 7 years, 6 months ago by fleetwin.

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October 8, 2016 at 2:36 am #5450
amuller
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Well, having spent more time than expected fiddling the ’62 into good running shape, I could not resist a nearly-unused ’73 for the asking price of $20 at an estate sale. so I’ve been comparing. Seems to me most of the changes are improvements:

better/simpler choke control.
shorter/more accessible fuel hoses due to connector moved to starboard side.
sometimes problematic shock absorber in drive line eliminated.
Is supposedly a 50-1 motor (though apparently still does not have needle bearings on wrist pins).
But the fixed main jet does NOT seem like an improvement to me. I can see some advantages, especially in the hands of users who don’t know how to adjust mixture, but as a long time engine tinkerer I like the ability to optimize the mixture for different conditions.

So, finally getting to my "ask," what is needed to convert OMC carbs to an adjustable main jet, and is there any strong reason not to do it? Can an older float bowl be swapped on? Can the existing one accept a needle and it’s gland and packing? (Not considering here the need to drill some sort of access hole in the pan…)
October 8, 2016 at 3:32 am #45421
Mumbles
Participant
If the original jet is correct for your elevation and hasn’t been reamed or drilled out, it should work just fine. I’ve never tried switching the bowls but I don’t see why that wouldn’t work. OMC did make kits for their fixed jet carbs to make the high speed circuit adjustable. Either way, you’re going to have to drill a hole in front to access the needle.

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October 8, 2016 at 4:05 am #45423
dan-in-tn
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US Member
Not sure what parts books you are looking at, but RDs & Big Twins have had wrist pin bearings since 1956 30hp. They kept getting better as far as the cage design, but by 1962 the bearings & cage on the wrist pin were fine much less ’73. Those motors are true 50/1 motors. Whether you chose to run them at that mixture is your own choice.
Same with the fixed high speed jet. Unless you are going back & forth with regard to altitude as Mumbles mentioned millions of motors of all brands are running with fixed jets. You have the last year (1973) for magneto ignition which is great! You don’t have to fool with the pesky low tension troublesome system that came along in 1974-1976. Just my opinion, I may be wrong.

Dan in TN
October 8, 2016 at 5:55 am #45424
amuller
Participant
quote t2stroke:

Not sure what parts books you are looking at, but RDs & Big Twins have had wrist pin bearings since 1956 30hp. They kept getting better as far as the cage design, but by 1962 the bearings & cage on the wrist pin were fine much less ’73. Those motors are true 50/1 motors. Whether you chose to run them at that mixture is your own choice.
Same with the fixed high speed jet. Unless you are going back & forth with regard to altitude as Mumbles mentioned millions of motors of all brands are running with fixed jets. You have the last year (1973) for magneto ignition which is great! You don’t have to fool with the pesky low tension troublesome system that came along in 1974-1976. Just my opinion, I may be wrong.

Dan in TN

Dan, I was talking here about the 5.5/6 hp fisherman motors. For sure the big twins have wrist pin brgs. Some say the little motors have some tendency to throw rods. Is that so?

As to fixed main jets I see pros and cons … just wanted to know the options.

Thanks.
October 8, 2016 at 2:01 pm #45432
dan-in-tn
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US Member
Sorry about that! My mistake. Posted that late last night and didn’t notice your change from 40hp to Fisherman even though it is right there in the title. DUH! The big end of the rod picked up rod brgs in ’61 before the six horse that allowed it to be much better about NOT throwing rods. The wrist pin end was not so critical. A fully jeweled powerhead is always nice, but not so crucial.

Dan in TN
October 8, 2016 at 8:00 pm #45453
fleetwin
Participant
US Member - 2 Years
I would agree with the original posting, for the most part, the 6hp models are in general, an improvement of the 5.5hp models they replaced. I think you are thinking of the 10hp models when you refer to problematic wrist pins with no bearings. Like Dan says, plain wrist pin bushings are not a problem on these smaller engines, even at 50:1. I have never seen one of these engines with any wrist pin wear issues.
I have never had any calibration issues with the fixed high speed jet on these engines. Like Dan says, running the engine at higher altitudes would be the only reason to consider swapping over to the adjustable needle/bowl set up. Keep in mind that the 6hp engine pan will get in the way of the adjustable needle, making the adjustment process a bit more inconvenient to perform.
October 9, 2016 at 3:26 am #45480
amuller
Participant
The 6 hp seemed in such good shape that I popped it in the barrel as-is and it ran pretty well. Of course it needs to be serviced before any serious use.

Also have an ’85 which is a substantially different design. Much easier to change the impeller!

‘Tis no wonder so many people continue to use these motors on a regular basis… I personally think the time period after they went to 50-1 but still had the regular ol magnetos is the sweet spot. (Not from the standpoint of looks, but for regular use.)
October 9, 2016 at 3:48 am #45483
Mumbles
Participant
The 5.5 and 6 horse motors have to be two of the sweetest running motors to ever come out of the OMC factories! ’76 was the last year for the older magneto ignition before they went to CD ignition which was used until the last six rolled out in ’79.

I’ve had literally dozens of these motors over the years and like to always have one or two on hand ready for trout fishing! You just can’t beat a well tuned 6 or 5.5 for trolling! ☺

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October 9, 2016 at 12:59 pm #45499
melugin
Participant
US Member
I have several of the ‘High Altitude’ kits for the small motor which is the adjustable high speed needle insert. Send me a PM and I ‘ll mail you one.
October 9, 2016 at 3:35 pm #45511
fleetwin
Participant
US Member - 2 Years
quote amuller:

The 6 hp seemed in such good shape that I popped it in the barrel as-is and it ran pretty well. Of course it needs to be serviced before any serious use.

Also have an ’85 which is a substantially different design. Much easier to change the impeller!

‘Tis no wonder so many people continue to use these motors on a regular basis… I personally think the time period after they went to 50-1 but still had the regular ol magnetos is the sweet spot. (Not from the standpoint of looks, but for regular use.)

Yes, the 85 models definitely win the impeller change challenge! I really like those 80s style 6-8hps, but they have a few engineering flaws, which is truly a shame. The driveshaft splines love to seize into the crankshaft, even on the newer models with the two seal set up….Those throttle cables rust out quickly in salt water and are way over priced and difficult to replace. And, there is a major flaw in the gearcase design, no bushing/bearing between the reverse gear and prop shaft bushing housing. This flaw leads to overheated gear lube, wear on the prop shaft bushing housing, and premature clutch dog failure. Even so, I still like these engines. Hopefully someday I can figure out a simple way to add a bushing/bearing.

But, in terms of reliability, and idle quality, nothing comes close to the old 5.5/6hp models….
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