1962 Evinrude Twin 40hp Lark IV Problem

[SprocketDog]

A little history first.

I bought boat and motor knowing the lower unit was out and have never heard it run before this but know the guy I bought it from real well and trust what he told me.

He said it would do around 30 or so and did until the LU went out

With the help of all you, I rebuilt the LU which the only time I had it on water shifted and worked like it was supposed to .. but the engine ran like crap and sneezed, surged, 19 mph top (1 cylinder I'm sure)

Time to do the engine .. new water impeller, cleaned carb, new coils, points(set to 20), condenser, plugs(set to 30), new fuel lines, link-sync.

The armature plate had a little slack but I didn't consider it a wobble, just slightly loose

It will start and run and gives me time to set LS air then at a steady throttle it will hammer and almost kill itself. The whole engine jerks when this happens and sometimes kills out

It may set and run fairly smooth at a fast idle, then I bring it up and down a few times and it starts the missing(jerking) stuff and seems to be a minute or two after I first start it.

Squeeze ball has no effect on anything

Compression 100 both cylinders, 24 to 1 mix (30 wt. motor oil)

I have a induction timing light and watched both plug wires and never caught any ignition skips

I Sea Foamed the cylinders and let set then sprayed in the carb while running

I'm in a barrel and did see crap come out and may have helped a little, but not fixed ... nearest lake 200 mi round trip and don't trust it in the Salmon River yet.

I didn't have a spark jump tester but making one and will check that later tonight

Is this symptoms of read valves or what the hell is going on.

Should have taken it to Midas ..

Thanks

 

[F_R]

Re: 1962 Evinrude Twin 40hp Lark IV Problem

A little history first.

I bought boat and motor knowing the lower unit was out and have never heard it run before this but know the guy I bought it from real well and trust what he told me.

He said it would do around 30 or so and did until the LU went out

With the help of all you, I rebuilt the LU which the only time I had it on water shifted and worked like it was supposed to .. but the engine ran like crap and sneezed, surged, 19 mph top (1 cylinder I'm sure)

Time to do the engine .. new water impeller, cleaned carb, new coils, points(set to 20), condenser, plugs(set to 30), new fuel lines, link-sync.

The armature plate had a little slack but I didn't consider it a wobble, just slightly loose

It will start and run and gives me time to set LS air then at a steady throttle it will hammer and almost kill itself. The whole engine jerks when this happens and sometimes kills out

It may set and run fairly smooth at a fast idle, then I bring it up and down a few times and it starts the missing(jerking) stuff and seems to be a minute or two after I first start it.

Squeeze ball has no effect on anything

Compression 100 both cylinders, 24 to 1 mix (30 wt. motor oil)

I have a induction timing light and watched both plug wires and never caught any ignition skips

I Sea Foamed the cylinders and let set then sprayed in the carb while running

I'm in a barrel and did see crap come out and may have helped a little, but not fixed ... nearest lake 200 mi round trip and don't trust it in the Salmon River yet.

I didn't have a spark jump tester but making one and will check that later tonight

Is this symptoms of read valves or what the hell is going on.

Should have taken it to Midas ..

Thanks

You can't be running that thing over a fast idle in a barrel. The hammering thing is a puzzler. It might be the vacuum cut-out switch doing it's thing, but I really don't think so.

 

[lindy46]

Re: 1962 Evinrude Twin 40hp Lark IV Problem

You say you cleaned carb - did you install a carb kit and float? If not, try that.

 

[tmcalavy]

Re: 1962 Evinrude Twin 40hp Lark IV Problem

Had a 59 Super Sea Horse 35 hp that did that, then backfired and blew a hole in the head gasket. Never figured it out...flywheel hadn't slipped, ignition and carb were good. Came with an old boat I drug home. I'd go through the carb again and check the fuel tank...even small bits of crud can mess up your carb and make it run bad...sounds like the slow/idle speed circuit is still dirty. Wouldn't give up on it until you try a different carb though...they're plentiful/cheap. The big twins run great when everything is right and are very reliable.

 

[SprocketDog]

Re: 1962 Evinrude Twin 40hp Lark IV Problem

I'll swear this thing kicks against the starter sometimes while starting and yes, I am moving it to start position

When it what I call hammers, it sounds just like you hit the crack case with a hammer, like it's pre-firing the other cylinder in reverse

Fly wheel key is all good and looks like new.

It seams to hammer (kick back) when bringing the idle to slow.

Here is how I checked the sync-link:

On this fixed cam, I put the cam mark on the pointer just starboard side of the cam roller

Loosened the eccentric lock and held the throttle butterfly closed and moved the eccentric until all slack was gone with roller just touching the cam

It has a fuel saver rod adjustment which I opened the throttle until the armature plate was just stopped by the stop block in the rear but not any farther. I then moved the throttle control rod collar to the pivot pin and set the lock screw (it was real close originally)

Did I do it right?

I just did the spark jump test and both will jump 1/2" blue spark

Other than point setting, isn't this about all the timing that can be done on this motor?

F_R, I never take it out of neutral and never to fast on rpms. If I get it fixed in that range, then a lake run will be next

 

[coolguy147]

Re: 1962 Evinrude Twin 40hp Lark IV Problem

could u get a video? of whats happening.

maybe recheck ur points and clean and regap at .020 also re-torque flywheel to proper torque

maybe major air leak?

 

[samo_ott]

Re: 1962 Evinrude Twin 40hp Lark IV Problem

BTW, instead of 30 weight oil, you should be using TCW-3, oil specifically made for 2 stroke outboards.

 

[SprocketDog]

Re: 1962 Evinrude Twin 40hp Lark IV Problem

cool guy, this same thing happened before I did the coils-points-condenser and plugs

I did all new above and gaped to 20, 105 fp on torque and re-checked after I ran it and warmed up, still 105

Air leak ?? where do I check

samo I know some say TCW-3 but this motor says right on it just plain 30 wt

I don't think would cause this problem, do you?

Don't have a camcorder, so can't do a video

Thank ya both for the come back

 

[tx1961whaler]

Re: 1962 Evinrude Twin 40hp Lark IV Problem

The 30 weight won't really hurt anything, if you were using the same non-detergent, single weight oil that was available in 1962. If you were using a detergent motor oil, then yeah, you were hurting it. They recommended 30 weight back in 1962 because that was all they had. Use TCW-3 2-cycle at 24:1 and you'll be better off.

The other problem sounds like it is running lean, and could be from misadjustment, a still clogged carb, or an air leak. I check for those by spraying around with a can of WD-40.

 

[ryendube]

Re: 1962 Evinrude Twin 40hp Lark IV Problem

The 30 weight won't really hurt anything, if you were using the same non-detergent, single weight oil that was available in 1962. If you were using a detergent motor oil, then yeah, you were hurting it. They recommended 30 weight back in 1962 because that was all they had. Use TCW-3 2-cycle at 24:1 and you'll be better off.

The other problem sounds like it is running lean, and could be from misadjustment, a still clogged carb, or an air leak. I check for those by spraying around with a can of WD-40.

mebbe explain. Ive done this with cars but not a small 2 stroke I imagine the same thing though. You spray (he uses wd) around intake,carb etc and listen for the motor to surge. your adding "fuel" if their is a leak. the vaccuum of the motor will suck it in if there is a leak. whereever you are spraying at the time check for gasket failure, cracks etc...

oh and when I say around i dont mean get any in the carb. Its past that point your checking, ie the base of the carb and back.


* use 2 stroke oil, dont use 30 weight non detergent. its not designed for 2 strokes.

 

[SprocketDog]

Re: 1962 Evinrude Twin 40hp Lark IV Problem

Thanks ryendube

I just removed the carb again and all jets ... seems clean to me. I used a 100 psi compressor and cleaner before, but I just ordered a OEM rebuild for it anyway.

I think it comes with some welsh plugs so this time I'm going into the passages and should be squeaky clean, if it don't fix it, I can sell it to NASA

I was wanting the new type plastic float but it pictures it with the cork again but at least it will be new

I will use TCW-3 if I get it fixed, right now I can't have over a 1/2 gallon of this through it.

PS: I did try the spray test before I tore it down this time around intake, hoses, gaskets etc. and used straight gas ... no difference

 

[ryendube]

Re: 1962 Evinrude Twin 40hp Lark IV Problem

Thanks ryendube

I just removed the carb again and all jets ... seems clean to me. I used a 100 psi compressor and cleaner before, but I just ordered a OEM rebuild for it anyway.

I think it comes with some welsh plugs so this time I'm going into the passages and should be squeaky clean, if it don't fix it, I can sell it to NASA

I was wanting the new type plastic float but it pictures it with the cork again but at least it will be new

I will use TCW-3 if I get it fixed, right now I can't have over a 1/2 gallon of this through it.

PS: I did try the spray test before I tore it down this time around intake, hoses, gaskets etc. and used straight gas ... no difference

NP, the cork float is fine (imo better cause its original) the only problem with cork is you have to replace it once in ahwhile cause the coating breaks down and the float saturates causing it to not umm "float"