Ski Twin 40

[haventaclue]

Another long shot,the plug could be done.When it heats up a fine crack opens in the core.It has been known for a brand new plug to fail.

[Rapier]

Yes, last shots are HT leads - on order from a bike shop ...and new plugs. Sort of discounted the leads when I checked on meter readings, but the twisting and pulling motion of the magneto plate movement could easily be the problem.

[Rapier]

Finally got a common rpm reading off the Merc-O-Tronic today on both pots, on half throttle, but will do a water test up the river tomorrow. New leads made up, new plugs fitted and have disabled my kill cord wiring until I know it isn't the cause.

[haventaclue]

disabled my kill cord wiring

Don't lean too far over the transom then ,good luck

[Rapier]

Lovely trip up river today and another 20 litres for 8 miles; something very amiss, despite the towing of a family Wayfarer - cleaned the carb out and reset the needles - toyed with the idea of fitting Mike T's spare recon carb, but my high speed needle way out - that's the final issue. Another 40 litres onboard for tomorrow's run.

[Rapier]

In the absence of a factory manual for this motor I've swapped over to a fixed high speed jet carb. I keep looking at the high speed needle and wondering why it's not a needle and it bears no resemblance to the carb types in the Seloc and Clymer manuals with both LS and HS diagrams. If anyone has an old Gale 40 manual it may help?

Another glorious day in the sun on the water with a beer at the Horse & Jockey. Bar the 3 fishing lines out over the slipway when I was coming in to recover... awrite mait.

[floater]

Appreciate that my 71 Big twin is very different to your Ski twin despite being the same year and HP. But just for comparison the Big twin and my 72 Norseman 40 both have carbs with only low speed adjustment, fixed high speed. I have a manual for a 69 Johnson 40 that also shows only a carb with only low speed needle. I would definitely try a different carb yours sounds a bit odd

[water_buoy]

I'm not sure if this will help you at all but I've found an exploded drawing of a 1965 carb for a 40hp
http://www.marineengine.com/parts/johns ... etor+Group
Do you know what year your engine is? If so you could probably find an exact one on that site but I think they are much the same aren't they?

[Rapier]

Thanks for that link - that's the fixed high speed jet version, common from the early 60s on. The Ski Twin 40's a model 40103B and the carb is supposed to look like the link below, but the high speed needle on my carb bears no resemblance. I think for those models they went back to the pre 1962 setup to get rid of excess parts before the 72 models arrived. It bears more than a striking resemblance to the Gale 40hp - I will investigate with a Gale model number. My cylinder head looks more like the early 35s too. It has no thermostat...perhaps was for certain european markets....

http://www.marineengine.com/parts/johns ... Carburetor

I swapped over the carbs last night, which is fine in the soup drum - had intended to do another test today, but it's windy and the spring tidal falls in the afternoon make self recovery a bit of an art. Revolting slipway that, was up to my elbows in a large diesel spill on Sat afternoon, my barely used waders will never be the same again.

[floater]

The carb in the exploded parts drawing shows a high speed needle with a reduced diameter at the jet end. Is it possible that your needle has had its end accidentally broken off by a previous owner who the just screwed the remains back in

We have mused in the past over 71 OMCs being bitsas so I think you are correct in your assumption that it is a parts bin special, my Big Twin has more in common with a 68 model than the supposed parts list for a 71 as its serial and livery say it is.

Be interested in how you get on with a different carb