New LighTwin Owner

Just scored this http://minneapolis.craigslist.org/hnp/boa/2985752590.html, looking for the basic information: year of manufacture, fuel / oil ratio, and things to look out for. Fortunately, the little town closest by our lake has an excellent marine mechanic who specializes in "vintage" 2-stroke motors.

Re: New LighTwin Owner

Need the model number, Underblog. Tentatively, the fuel ratio will be 24:1, TC-W3 certified outboard oil and 87 octane unleaded. Plugs will be Champion J4C or J6C gapped at .030"

Lightwins are, along with Johnson JW and JH, the best outboards ever made. Love her and she will love you right back.

Congratulations on a great acquisition.

Re: New LighTwin Owner

Going from the visuals, I am thinking that this is a 1964. Almost certainly it lacks needle-bearings, so the 24:1 ratio sounds right. Once I get back close enough to read the label, I'll get the model number. I will do right by this motor!

Re: New LighTwin Owner

Here are the numbers, Model # 3502A (1965 then?), Serial # B36212. Powered an Alumacraft canoe, so it should push my Grumman along just fine.

Re: New LighTwin Owner

1965 is correct. I'd run it at 24:1, because it does not have a full set of needle bearings on key parts.

Re: New LighTwin Owner

I take it the Lightwins are primer enrichened, rather than choked off at the carb? I am trying to determine which starting procedure to look at in the FAQ. I will be picking up a manual for the motor; they seem readily available on FleaBay. However, in the meantime, I want to learn as much as I can before I attach her to the Grumman and put her in the water.

Re: New LighTwin Owner

64 on up light twins are 50:1 per my 2 aftermarket service manuals.
Also the 64 5.5 is 50:1, the 5 and 6 hp 65 on are 50:1 near as I can tell they don't have needle bearings but special
bushings and may circulate excess crankcase lube to the main bearings. I would suggest running a little rich though
to guard against mixing errors.

Re: New LighTwin Owner

While my 1964 OEM Manual agrees with your aftermarket manual, Steelespike. The majority of experienced OMC wrenches here want the friction bearing motors to stay at 24:1 up to about 1970, when they went frictionless.

Many people do what OMC said to do in 1964. . .switched to 50:1 for all '64 and later models, and I have read no complaints. But Joe Reeves offers pretty convincing arguments for 24:1 in all friction bearing engines.

OMC's decision to specify 50:1 in all 1964 and later outboards was market driven, not engineering driven. I don't know that it caused any harm, but I do know that the 1980s decision to call for 100:1, also market driven, did do harm.

Like you, I am a strong believer in doing what the maker says to do, so long as it causes no harm. I also believe in treating outboards as though they were my own children.

Given Joe Reeves' arguments, friction bearings and the fact that 24:1 cannot harm a 1965 model that is identical to pre-1964 models that required 24:1, I think 24:1 is the safer solution than 50:1.

Re: New LighTwin Owner

Underblog said:

I take it the Lightwins are primer enrichened, rather than choked off at the carb? I am trying to determine which starting procedure to look at in the FAQ. I will be picking up a manual for the motor; they seem readily available on FleaBay. However, in the meantime, I want to learn as much as I can before I attach her to the Grumman and put her in the water.

Click to expand...

your engine has a choke knob ( push pull) , as well as a low speed adjustment knob.
(when did they change these motors to the fixed high speed jet??....just picked a jw21 (1966) and it also has the fixed high speed jet)

Re: New LighTwin Owner

I bow to hands on experience. And time has taught me to err on the side of caution.
I think I lost sight of the fact that Oil is the life blood of any motor.

Re: New LighTwin Owner

My assumption always was that if OMC said 50:1 then I'm ok with it. These engines are still plentiful and assuming all the owners in the last 50 years followed the manufacturers instructions and ran em 50:1 and they're all still running now then it must be ok! If we saw lots of lightwins up to '64 and then they seemed to be no more on the open market then we could have made an educated guess as to why!