1958 John 35 compression results

[tnltracy]

So I was able to borrow a compression gauge today and checked my 'new' old engine. I got 80PSI in both cylinders. From my reading, certainly not the optimal 100+ that is suggested, but not at the low end of some readings I've seen here.

Engine ran fine on my initial run, although the rev up seemed slow getting from low speed up to top speed. And not having a tach, I really don't know if I'm even getting to the optiomal 4500 RPM

My questions then are:

1) Is it OK to run for now, and plan to dig in more and potentially overhaul over the winter?

2) I've read suggestions for either Marvel Mystery Oil, or Seafoam decarb the engine. I don't have any easy way to get the engine up sideways, but can get it as high as the tilt will allow. Would either of these (or something else) make more sense as a first step to see if I can get the compression up?

3) Any other thoughts or suggestions?

THis is a new to me engine which I just rebuilt carb on, and have run only once at this point. It idles nicely, runs fine at high RPM, just doesn't feel real strong to me. But, this is my first engine, so I may be expecting more than a 50 year old 35 HP engine will do. It's on a 14' aluminum boat, so really should be fine, but I wasn't able to get the boat to plane on first run.

 

[CATransplant]

Re: 1958 John 35 compression results

That's the same compression mine had, and it ran fine. What I think is happening for you is that the engine's running on just one cylinder. Try checking spark on both, and see what you find.

If, indeed, it's running on just one cylinder, given what you've already done, I'd start looking at the kill wire circuit. You should do this on the water. First, try disconnecting the black wire that goes to the the mercury switch on the right side of the engine as you look at the front of the engine. Then, carefully, since that disables the safety feature that prevents starting in gear, try a wide open run. If the problem still persists, reconnect that wire. Then, remove the wire that comes from the flywheel and goes to the vacuum safety switch on the left side of the engine, as you look at it. Try another run.

In either case, if the test fixes the problem, then you need to replace the safety feature, either the mercury or vacuum switch, for safety's sake.

You see, if either of those switches are defective, it kills one cylinder.

Next, if that still doesn't help, try disconnecting the two black wires from the M terminals on your ignition switch and try another run. You can stop the engine with the choke...no problem. If that fixes it, it may be a short in one of the wires or a defective switch. That was the case on mine, and I ended up just forgetting the switch for those wires and used the electric choke to stop the engine at idle. They were shorted somewhere in the cable.

If that still doesn't fix it, then it's time to check your points again. Make sure they're spotlessly clean. You should be able to access them through the port in the flywheel, if your flywheel wasn't replaced with a later model.

Report back when you've done this and we'll go from there. The symptoms you describe are precisely those of a dead cylinder. Don't worry too much about the compression, as long as the two cylinders match.

 

[rolmops]

Re: 1958 John 35 compression results

You may want to adjust transom height because that engine should really make your little boat take off.
The compression is quite low for that engine.They usually sit around 120#.
Pour some Marvel Mystery Oil in the cylinders.It will loosen the carbon build up and allow the rings to do their job.Then take another reading.
If you think that she runs on only one cylinder,pull first one spark plug wire and see if it still runs,then put that one back and pull the other.If your engine quits with one of the plug wires disconnected,you know that the cylinder with the connected wire does not fire

 

[tashasdaddy]

Re: 1958 John 35 compression results

agree, that motor will run on one cylinder. also in which hole is the tilt pin. you could try moving it in one hole and then out one hole. don't drop it in the water, they are expensive.

 

[tnltracy]

Re: 1958 John 35 compression results

Thanks for the feedback so far folks.

I acutally just got all of the wiring set up properly, including the kill switch. I can still check it, but it seems fine in that it shuts down properly when I turn key off. How would it's impact on higher RPM be seen? The motor is definatly revving up, it just seems to do so slowly.

I got a spark tool and confirmed I have spark at both cylinders, so I should be Ok there and running on both.

Re the points, anyone have a picture that will show me the ports for adjusting them? I have a couple small oval marks in the flywheel, but they don't seem to go through. Nothing else seems to have been replaced, so I doubt the flywheel was, just not sure how to 'open' up the ports.

I will also adjust the motor down a notch in angle. There's a couple notches left so I will give that a shot. I'm actually beginning to wonder if the PO ever actually ran this boat with this motor. I know from the paperwork that it previously had a Evinrude 33 on it, just not sure when he swapped them

 

[tnltracy]

Re: 1958 John 35 compression results

One more thought: I'm wondering if my throttle linkage is set correctly. It appears that the throttle itself doesn't even begin to open until I'm nearly at full throttle on the controls. I think I need some adjustment there as well.

 

[CATransplant]

Re: 1958 John 35 compression results

That could be. A link and sync will fix that. The process should be described in your manual. If you do have spark on both cylinders, then you can forget the kill wire deal, except for one thing. The mercury switch may be mismounted and shifting into gear may be causing it to short one cylinder. It's unlikely, but possible.

If your RDS-20 is running right, it should pop that boat right onto plane and accelerate quickly to it's max RPMs.

 

[CATransplant]

Re: 1958 John 35 compression results

As for the points, the original flywheel for that engine had an oval plate held with two screws on top of the flywheel. Removing the two screws let you access the points through a hole in the flywheel.

However, some of those flywheels developed cracks and were replaced with one without the access port. All the Big Twins from 1959 on had the new design flywheel. A lot of the earlier ones had the flywheel replaced by the dealer.

 

[rolmops]

Re: 1958 John 35 compression results

The only way to adjust the points on that engine is by removing the flywheel.The 1957 still had the through flywheel adjustment port ,but they stopped making those because there were problems with stability of the flywheel.If you have the flywheel off already,you want to replace whatever needs it,because unless you have the right tools it can be a female dog of a job.

 

[CATransplant]

Re: 1958 John 35 compression results

The 1958 RDS-20 also had the port in the flywheel. Mine did, and there's a note in the Master Service Manual about it. They recommended changing the flywheel on them to the later model. Apparently, there was a service bulletin to that effect. Mine was fine, though, with no cracks, and it was sure nice to be able to adjust the points without pulling the flywheel.

 

[tashasdaddy]

Re: 1958 John 35 compression results

this is what it looks like under the flywheel. these coils are shot. because the kill wires, had 12 volts put to them, buy accident.

 

[tmcalavy]

Re: 1958 John 35 compression results

Run some Seafoam through that puppy. The link and synch is basically this: move the throttle from Stop/Slow to Start; check the cam roller in front of the throttle advance plate, the roller should just be in contact with that plate; look down the carb throat with a flashlight, the back butterfly should be cracked just a hair; slowly move the throttle to Fast, have the motor in gear; the back butterfly should smoothly/gradually open full bore as the throttle is advanced to Fast. If it's out of synch it'll be obvious as you watch the butterfly. The factory manual will explain how to adjust the throttle plate or cam roller to initially adjust the sync. It's trial and error, but real simple...a spotless carb helps alot too.

 

[tnltracy]

Re: 1958 John 35 compression results

Quick update, and thanks again for the input guys!

I confirmed the circuits are all operating as expected with confirmation of open/closed state for both the mercury switch, and the vacuum cut off:

Mercury switch closes just beyond the stop point imposed by the shift lever being in neutral. Also confirmed beyond that point that the starter does not engage if powered.

Confirmed the vacuum cut off is closing with vacuum applied via test hose.

So those items out, I went on to the throttle/timing advance components. I confirmed that a. the initial throttle control via the roller to cam was quite out of sync, and engaging very late and b. the throttle override at WOT setting was also off by quite a bit. I set it up per the shop manual so when the timing indicators line up on the cam the throtle is just 'cracked' from closed, then opens gradually as throttle is applied, and the secondary opening to WOT occurs properly as timing approaches full advance. Per the shop manual, I also confirmed that I can then pull the throttle back just a bit which changes the carb setting while leaving the timing fully advanced, thus engaging the 'fuel saving feature' of this engine.

Anyway, that done, it'll be the weekend before I likely get to run it again due to the poor weather expected for the next few days. If that changes and I can get it out on the water and try things out I'll report back sooner.

Oh yea, the flywheel is definatly a replacement and has no window to set points. If I still find poor performance this weekend, I'll get a puller and go after the points and coils. My test today suggested good spark, so I'm hoping I'm ok there for now.

I did pick up some marvel mystery oil, and if I get time will tilt up the engine and do that treatment before the weekend to see if I can bring back higher compression as well.

 

[tashasdaddy]

Re: 1958 John 35 compression results

sound very promising.

 

[CATransplant]

Re: 1958 John 35 compression results

That out of sync situation could have caused the problem, for sure. I hope that correcting it will give you full performance. We'll be eager to hear what you find!

 

[tnltracy]

Re: 1958 John 35 compression results

Wow! what a difference a little tuning and adjustment makes! You all were right, this little 35 really moves the boat along. With the throttle linkage adjusted, and the motor one notch lower, it jumps right up out of the water above half throttle.

I'll be out today with some friends and family and will try to get pix of the boat in action for you all to see

I also changed the lower unit oil yesterday, and put some Marvel Mystery oil in the cylinders last night. Had some water in the oil, and of course, I pulled the wrong lower screw and removed the shift linkage pin which took me an hour of jiggling and shuffling to get back in properly. Shop manual drawings led me to that being the drain screw when it's actually underneath on my model.

 

[tashasdaddy]

Re: 1958 John 35 compression results

you got really lucky. glad to here you're up and running.

 

[CATransplant]

Re: 1958 John 35 compression results

I'm so glad to hear your gold and creme beauty is running right and shoving your fin boat along smartly. I knew it would, and it's a perfect match for that boat. You'll be the envy of many on the water, I'm sure.

Now, just keep up with the routine maintenance and enjoy your boating!

 

[samo_ott]

Re: 1958 John 35 compression results

Another happy ending

 

[tnltracy]

Re: 1958 John 35 compression results

Took friends out today for a couple hours and got a good amount of running time on the motor. Runs very nice at WOT, and chugs along smartly at low RPMs as well. I'm noticing a 'skip' of sorts that seems to be every several revolutions of the motor. Not quite sure what it is really. Seems to occur far enough apart that it's not each rev of the engine or prop. sort of 'harmonic' in nature. Anyway, maybe it's just the nature of a 50 year old engine. It doesn't seem to effect performance.

Did a bit more tuning of the low idle jet and getting better low idle running now as well.

Hopefully will get my wife to take her first trip with me tomorrow along with my boys. She took a couple pix today of the boat in the water which I'll post once I get them downloaded.

A big thanks again to all who have helped out and given me their input through my this prep and tuning. I'm very happy with the results.