TOPIC: Ski Twin 40hp Running Issues

I have the pre '72 Norseman clearout from Evinrude Belgium, a model 40103 Ski Twin from 1971. It is a budget model that utilised the last Ski Twin 33hp parts with a 40hp block, adjustable low and high speed needles vs. the fixed high speed common on late model BigTwins and including a non shrouded mid-section, more in common with the late 50s 35hp BigTwin and might have run a tiller arm at some stage as it has an open end without the start/slow/fast hand throttle. I cannot get it to run properly and believe it to be a synchronisation issue now, but need some advice as the marks all appear to be correct. It will not throttle fully out to max RPM and sounds as if the ignition is retarded, plus the throttle stop is not fully home against the stop at WOT. I have newly fitted a fuel pump, carb kit, coils, plugs, condensers, points, pump housing, impeller - the usual service items - have cut back the HT leads and get 4.5ohms on a resistance test and checked the anti-pop too. Compression is 130 on both cylinders and it's run on a a diet of 50:1, but consumption is very high. It's very possible that someone has fiddled with the motor settings, as it was at least 2nd hand when I bought it, but in largely unmarked condition - i.e indicating that it's life had not been hard. Anyone with knowledge of this hybrid? I've run out of ideas.. even entertaining a check that the throttle arm was not bent.

This may not be of any help, but... The general description of your motor appears about the same as my '63 Gale 40hp...Good luck

with the engine NOT running ck you throttle stop , carb wide open, if all is good ck the prop for pitch issues. in fact I have had the same issues with an ol 40hp. mine was a cheep aftermarket prop. it lugged and was very slow. and used alot of gas.

Post the same picture as in the first post, but with the control in the slowest idle position.

Professor I looked at it again today versus a '64 (RDS-26S) Johnson that I pulled the flywheel on and made the synchronisation changes to the Ski Twin (40103) using the Clymer 40hp setup D & 5 - tried to copy the setup, but the Johnson has a fixed h/speed needle and a different screw setup on the throttle arm. Not sure if I have it spot on now? The only issue I see now is that the HT leads meet marginal resistance as they run across the block when the armature plate moves to the full throttle position...and sometimes the stop is not quite reached. Am not sure whether bending / replacing the control lever spring will improve it, or whether it just relates to the way the leads were routed?

a. Throttle closed - synchronisation as setup today
b. Throttle closed - Cam follower at point where throttle shaft just moves imperceptably

c.Throttle wide open
d. Throttle wide open following synchronisation setup today - throttle shaft no longer rests on stop on carb (it was dead against the stop yesterday, but the armature plate looked like it wasn't far enough across and did not touch the stop on the block ) - ignore the rod from the cam follower to locking lever - it's not in the way in the pic.

e. Throttle rod control setup to 1/32th in (this is at WOT though..)

Still not convinced, but I have little experience on these motors, so doubts do persist..

Prop wise I've run a multi pitch prop set at 12pitch, and 10ish by 11pitch (my boat weighs in a about 200lbs without the motor, all up about 650lbs with self, 6 gals of fuel, battery and motor and boat).

Here's what it looked like yesterday - throttle closed. The 2 marks on the cam align with a cast pointer on the front of the block (out of view)

The resistance of the spark plug wires probably isn't the problem. If the wires are stiff & don't allow the free rotation of the magneto plate, replace them. By removing the magneto plate, you have an opportunity to clean and lubricate the bronze bushing that the mag. plate moves upon. Also check on the primary leads over on the other side of the engine to see that those aren't getting stuck or caught on something that would prevent free movement.

Have you repaired the bent / distorted throttle arm on the carb? The arm is distorted and the lever openings are no longer in alignment. The lever should not be skewed to either direction - This must be corrected. I'm guessing that the throttle stop bushing was incorrectly set and this caused the arm to be bent by trying to force the control at the helm. I've attached a picture of the throttle arm actuator for you to look at. The brass bushing with the set screw must not come into contact with the throttle arm bushing until the magneto is fully advanced. The magneto stop arm should be firmly against the block prior to these two bushings contacting each other. The remaining 1/3 to 1/4 travel of the throttle is all at the carb, - not the magneto.

I hope this helps

I spent the morning bending it back to look the same as a spare I have and setting it up. Does the throttle shaft need to be fully against the stop on the carb, i.e. fully open when the magneto plate is up against it's own stop? And then the set screw tighten up? I noticed, on the Johnson, that there was a little movement left in the throttle shaft at wide open throttle (but that could just be because that motor isn't setup yet..).

Although the magneto plate was clean and reasonably greasy, I did a proper job on your recommendation and replaced the fuel pump which wasn't right one for the motor - I guess they got the part numbers mixed up, as the arm was fouling the top of it at part throttle. Nice sunny day here, but tides a bit odd and too short notice to do the final on-water check with my test prop - I'll try it out next weekend and report back.

Thanks very much, greatly appreciated! I was tearing my hair out; will teach me..

Look at the picture below. Loosen the set screw on the brass collet marked "A" . Slide the collet forward and away from the throttle arm on the tower shaft. Move the main engine throttle to the fully advanced full throttle position and hold it there. The magneto plate should be fully against the stop mounted to the engine block. With the engine throttle held in this position, open the carburetor fully, and hold it in the full open position. While both the engine throttle and carb are fully maximum positions, slide the collet "A" back to the point that it is snug up against the bushing "B" and tighten the set screw. Now return the engine throttle to idle. The carb should be fully closed down to the idle stop. The collet "A" and bushing "B" should have a fair amount of distance between each other. Now - open the engine throttle and watch the magneto plate advance. The bushing "B" should not come into contact with the collet "A" until the magneto has stopped advancing and is FIRMLY against the magneto stop. Up to this point, the only opening (and it is only slight) of the carb has been accomplished by the rubber roller contacting the low speed throttle ramp on the magneto plate. At this point, the collet "A" should be near to touching, or up against bushing "B". The engine throttle is probably at about 2/3 to 3/4 open at this point. Upon opening the throttle even more - the last 1/3 to 1/4 of it's travel - the bushing "B" pushes against collet "A" to open the throttle of the carb. Keep in mind, that when moving the engine throttle, the carb will barely open until the last 1/3 to 3/4 of the throttle travel. Also, the engine must be in forward gear when doing these adjustments, as there is a safety lock-out when it is in neutral and reverse to prevent wide - open throttle run-away.

Done! I hope to test it properly before a river run (at walking pace) next weekend. Thanks for the help again.

Out today for the 1st time, but whilst there is some improvement, I think (on anything other than idle and in-gear, running at a walking pace) that I have a problem with the bottom cylinder's spark which was cold - probably the HT lead as the electrics are new. This is at 1/2 lever (old Shipmaster style controller), being throttled up. Ugh,..this is the video I shot which is how it runs at full throttle.

Sounds like you still have an ignition problem, take the mag plate off, replace the spark plug wires with new copper core wire, and clean or replace the plugs again. Check all the wires coming off the coils you wouldn't believe how often I see a just tuned up motor with the wire going to the points either rubbing on the crank which wears it through in short order or pinched under the coil and shorting to ground. Make sure that the kill switch wires are not worn through and touching the mag plate they are normally run under the coils and will be flattened but they have a protective sleeve to keep them from shorting just check them while you have it apart. Next up is to re-clean the points and make sure they are in good alignment then set the gap. Once all is good put the mag plate back on then check for good spark. Once you have established that it is firing on both it's time to set up the carb. Disconnect any levers that allow for adjustment with the cowl on and make sure that the needles move smoothly with some resistance, if they move too easily snug up the packing nut a tad and check again if it is better fine, if not replace the packing and try again. Once it is determined that the packings are OK turn the low speed needle in until it gently seats then turn it out 1 1/4 turns, next seat the hi speed and turn it back about 3/4 to 1 turn, these setting will get just about any old OMC to run. Now that we know we have good spark and basic carb settings move onto the lake (fun) portion of the exercise. With a helper to steer and throttle the boat fire up the engine let it warm up for a min or 2 then head out gradually moving to wide open, once the throttle is fully against the stop start to adjust the high speed needle towards lean and it should speed up when you pass the sweet spot it will start to slow down, move back towards rich until best speed is achieved. Next up is the low speed, gradually slow down until idle and adjust the low for best smoothness and lowest speed without coughing, this is best done at the dock as it will probably stall several times during this process. Once the low is set take it back out for another run to make sure it is running well at all boat speeds, once you are happy reinstall any adjustment levers put the cowl back on and call it done!!!
If possible avoid ethanol polluted gas most marinas offer regular grade ethanol free on the dock and depending on where you live Shell may offer Vpower fuel without ethanol at their street pumps
Al

Thanks for the advice. Decent copper core motorbike HT lead on route and 2 new plugs waiting.

I am also wondering whether the wiring for the cutout switch is properly done, as that would close down the bottom pot too. I have an aftermarket lanyard type kill-switch (as we do a lot of rough water boating) that is wired into the original stop switch wiring. I will need to investigate with a Johnson 40 owning friend who understands wiring...

Unfortunately the UK has only ethanol based fuel, albeit at 5%, but it's expected E10 will arrive soon. There's no other substitute though.

Although you may still have some sort of ign problem, in the video it sounds to me like it's running way too rich.

Have you tried adjusting the high-speed needle while underway?....ed

New leads fitted with fresh plugs and runs fine at idle or just above idle. Took it out twice for extended runs over the weekend, but despite taking the carb apart on Saturday and looking for anything out of order, was unable to get the motor to throttle up to max speed / rpm on Sunday. Tried adjusting the HS needle backing out within the common 3/4 to 1 counter rotation (and further / nearer..), to no avail.

Eventually took the carb off and replaced it with a spare with fixed high speed jet, but it is as yet untested.

This is a pic of the carb and hs needle. I've never seen one like it though with that blunt end. The float bowl has a slightly smaller diameter hole than the needle. Thinking it may share a common carb with the 40hp Gale of '61/'62 I checked the manual, but that too has a proper needle shape for high speed.

I need to hunt down a factory service manual for this specific motor, as everything about it screams hybrid.

The blunt end on the hi speed needle is how it is supposed to be, not sure what to tell you now, hope the carb swap helps.

I did a quick internet hunt and bought a '71 Ski Twin 40103 manual for a 10th of what it cost me in fuel this weekend...

Clymer/Seloc manual's Type C or II carb adjustments refer to low speed needle counter clockwise adjustment of 1 & 1/2 turns and 3/4 on high speed.

The '71 manual says 1&1/4 (no big deal..) on low speed, but 3/8 on high speed. With the blunt shape of both the high speed needle and it's wide(r) orifice it would make a big difference. This pic shows it adjusted to spec, but it's almost seated...

The fixed jet carb will be probably tested soon, then used until I get my sense of humour back.

Your engine needs a set of coils if it revs up in neutral but falters under a load. The new coils usually have a green plastic cover on them. This will cure the problem

Thanks for the tip, these are fresh from the supplier, the new non-resinous versions tend to be black coloured over here though. I couldn't trust the older ones I'd fitted years ago before I mothballed the motor, so replaced them & the condensors and points as a matter of course.

Well, this might be a stupid comment but here goes. If your motor will rev in neutral but not in gear. Maybe some of the problem is the motor is WAY overproped? Just a thought, seems you have worked on everything else

The range of props on these is not overly wide - if you intend to run them fast. We use a big bladed 9/10 for slow river runs (speed/wash limits)and at the moment it's running a 13pitch. The boat is 160lbs without motor, about 650lbs all loaded, so will be fine.

Finally got out on the water today. Have swapped out the Ski Twin carb with a fixed jet version. It starts easily and idles smoothly - it now revs up to the max when not under load, i.e. not in gear. In gear and throttle wide open, I think it cuts the electrics to the bottom cylinder, as it won't rev out.

My question is the cut-out switch (which tested fine)...it cuts the electrical power to the cylinder when the engine is over-revved - load, or no load scenario(unsure?) Is it possible a. the diaphram is weak b. crank pressure is too high under load c. the tube from the front of the block to the anti-pop is at fault?

Really at my wits end on this one...It's about to be relegated to the back of the shed.

Just to recap. Coils are new, points are new, condensers are new, plugs are new, coil wires are new. None of the stop wires are crimped, exposed or earthing and I've disconnected my kill switch (deadman's). The carb is a rebuilt BigTwin fixed jet version. Compression is high and even, 120psi on both cylinders.

I think my problem is the cut-out switch, but I need to disable it to rule it in, or out. It certainly works and tests OK, but probably works too well, with excess manifold pressure created by using the BigTwin 40hp fixed jet carb with it's wider Venturi than the 33/40 Ski Twin carb.

Is it possible to disable the cut-out switch by blanking it off on the engine side and leaving all wiring position?

I have a kill switch wired in, on a lanyard - it cuts power instantly on an over-run (and man overboard scenario), so from a safety aspect I am covered.

Does this make sense? Does anyone know if this is a common problem on the 40hp Ski Twin?

The good news is am up and running, with the test prop am getting it to rev properly and the boat ran up to 30mph happily.

The anti-pop was not to blame and was reinstated post fitting of the new plugs - it turned out the new Champion J4J plug on the bottom cylinder was faulty, with a poor spark only evident with the tester attached.

Just wish to say thanks very much for the help.