1960 Lark II 40 troubleprone?

[Bellboy]

Hi all, I've heard there are/were problems with these engines such as crank/rods/keyways etc. Can anyone share their experiences please? I have an identical pair of these and would love to put them back in service but only if they can be made reliable.

Also looking for parts and shop manuals for this model 35521 as well as some parts sources.

If these powerheads are really problematic is there a substitute that would permit me to retain the original cowl? My goal is to keep the vintage styling, not so concerned with the mechanicals that are out of sight. Thanks

PS Photos aren't my engine, just the same style

 

[tashasdaddy]

Re: 1960 Lark II 40 troubleprone?

i know nothing about them being problems. they are great reliable motors. most parts are still available. do a compression check and spark, on them, and give us the results. i suspect they will need impeller, carb kit, coils, points, condenser, plug wire. $200-250 after that they should be good for 25 Years. they do run 24-1 fuel-oil mix.

 

[CATransplant]

Re: 1960 Lark II 40 troubleprone?

Those big twins are quite reliable. If they have good compression, it's easy enough to get them running perfectly. A pair of them on the back of a suitable boat would make quite a statement.

The only possible flaw is, after 50 years, if they were abused when shifting, the clutch dog may be bad. The part can be found. If they were treated properly, that shouldn't be a problem.

TD has run down the most common things you'll have to do to put them in top shape. They, they'll be as reliable as much more modern outboards.

 

[coolguy147]

Re: 1960 Lark II 40 troubleprone?

i heard that they have a run away problems. cause of the to small of crank shaft. so i guess dont really rev it to high in neutral like fluttering the butteryfly too much

 

[CATransplant]

Re: 1960 Lark II 40 troubleprone?

i heard that they have a run away problems. cause of the to small of crank shaft. so i guess dont really rev it to high in neutral like fluttering the butteryfly too much

You heard wrong. All two-strokes can run away. That's why you're not supposed to rev them in neutral. It has nothing whatever to do with the size of the crankshaft. Besides, the big twins have safety features to help prevent runaways.

If those engines were so bad, there wouldn't be so many of them out there, still pushing boats after 50 years.

 

[F_R]

Re: 1960 Lark II 40 troubleprone?

It is true that some of them broke crankshafts. That is why they increased the size of the shaft in later years. However, I was a dealer mechanic at the time and personally have never seen a broken shaft. And I have serviced hundreds of them.

Now about those flywheels and keyways!! Yes there are a lot of them out there giving trouble. And it is a direct result of inexperienced and/or stubborn people working on them. And the problem is not limited to that model. If you beat the flywheel off with a hammer and refuse to use a torque wrench to tighten the nut to the correct specs, you have just destroyed a motor. Nuff said.

 

[Bellboy]

Re: 1960 Lark II 40 troubleprone?

Thanks for the replies! I have 3 plus decades of being a professional mechanic but zero experience on outboards...am sure with the proper shop manuals and whatever special tools that I should be able to muddle thru by applying common shop procedures and common sense (in such short supply these days!)

One of the things I learned early on is to ask questions before diving into the unknown...best to take advantage of the experience of others and build upon that than reinvent the wheel by yourself.

The reputation of these first year engines has been told to me by several people but it's one of those he said/she said things with no hard facts. This site pretty much slams these engines: http://www.duckworksmagazine.com/04/s/columns/max/15/index.cfm but I don't put too much stock into the "I read it on the internet so it must be true" line of thinking so here I am asking for multiple opinions and real world experiences.

Seeing as these engines still exist at all makes me think that they are either still usable/rebuildable and may have received whatever upgrades or replacements of cranks etc years ago to have survived till now.

Are (were) there superior retrofit cranks? (or any other needed components) My goal is to retain the overall look of the unit (at least the cowl)...not too concerned with the hidden spinning bits.

Haven't taken a compression test as my plan is to tear into them and at the very least reseal and rering them along with new reed valves, complete tuneups, o/h the carbs, fuel and water pumps. During this I'll have the oppurtunity to inspect everything for any problems such as crank issues (bearings etc) cylinder wall condition etc etc. Thanks again!

The labor is inconsequential to me, my only direct costs are for the parts which I'll gladly pay for the peace of mind knowing that some 49 year old $4 knick knack won't end up stranding me.

 

[BigB9000]

Re: 1960 Lark II 40 troubleprone?

This site pretty much slams these engines:

As an owner of 4 of these engines, (40's and a 33) It was an interesting read.

However, I don't really think they are slamming the engines they are basically saying; yes they are old, but cheap and will do the job.

 

[F_R]

Re: 1960 Lark II 40 troubleprone?

The part number 307482 crankshaft in question was used in the 1960 and '61 40hp motors. The earlier '58 and '59 35hp powerheads were similar however most parts are not interchangeable. But the top main bearing is. The '62 introduced the new crank with a larger top main bearing and flywheel hub. There were also other bearing changes made. The '62-up powerhead is similar and can be used to replace the '60-61 if enough stuff is changed along with it.

However, as you suggest, there are thousands of those things still running around. They can't be all that bad. I wouldn't hesitate a minute to trust one on my own boat. Condition is everything. They have had plenty of time to experience misuse and abuse.

If I were to comment on something on the '60 that was worthless it would be that stupid water heated automatic choke. And the trailering tilt lock that usually broke. Pretty nit-pickey huh?

 

[Bellboy]

Re: 1960 Lark II 40 troubleprone?

As an owner of 4 of these engines, (40's and a 33) It was an interesting read.

However, I don't really think they are slamming the engines they are basically saying; yes they are old, but cheap and will do the job.

This is the paragraph that comes across (to me anyway) as a slam:

"There are some Big Twins that I would recommend that you avoid; 1960 and 1961 were the first two years of the 40 hp version and had some major stuctural problems; i.e. a reputation for shearing flywheel keys and even breaking crankshafts. Because of these problems, the powerhead for the 40 was completely re-designed for 1962, and the '62s and later 40's are very good engines."

The part number 307482 crankshaft in question was used in the 1960 and '61 40hp motors. The earlier '58 and '59 35hp powerheads were similar however most parts are not interchangeable. But the top main bearing is. The '62 introduced the new crank with a larger top main bearing and flywheel hub. There were also other bearing changes made. The '62-up powerhead is similar and can be used to replace the '60-61 if enough stuff is changed along with it.

Once I've torn these down I'll compare them to each other to determine what, if any, differences there may be. Their serial numbers are fairly close 15120 and 15185, makes me wonder if they were originally sold together and have been brother and sister their whole life.

However, as you suggest, there are thousands of those things still running around. They can't be all that bad. I wouldn't hesitate a minute to trust one on my own boat. Condition is everything. They have had plenty of time to experience misuse and abuse.

Common sense prevails...as unusual an occurrence as that may be LOL

If I were to comment on something on the '60 that was worthless it would be that stupid water heated automatic choke. And the trailering tilt lock that usually broke. Pretty nit-pickey huh?

Not nit-picky at all (my mentioning that there's no E in picky would be nit-picky LOL!!!)

I put great appreciation and value in picking nits as so often they turn out to be critical information that's ignored until too late. Thanks!

 

[freddyray21]

Re: 1960 Lark II 40 troubleprone?

I agree if it's still around running after all these years then it should be for awhile yet.

 

[tashasdaddy]

Re: 1960 Lark II 40 troubleprone?

i say go for it, you will get the experience you need. to work on your own outboards. if nothing else a great learning experience. thats how i started, and i was a carpenter. remember it is a 2 cycle not a 4 cycle. they are simple engines.

best service manuals are at outboardbooks.com

 

[Bellboy]

Re: 1960 Lark II 40 troubleprone?

Aye...next step after getting the manuals is to build a couple of motor stands to support the engines as I disassemble them.

I foresee lots of bead blasting in the near future LOL