Suzuki/Evinrude 70hp 4 stroke question

[digger]

I am rebuilding a basket case 4 stroke evinrude that I know nothing on the history. I have the motor running now, but it seems that the lower unit might have a problem -- I am not sure. I can move the shift lever on the motor rearward, putting the motor into reverse (the shift comes up on the lower unit), and it passes the detent and stays in gear. When I move the lever forward, moving the lower unit shifter down, I can feel a spring. This spring pushes the lower unit back into neutral when there are no shift cables attached. I'm sure that with cables and control unit attached the lower unit will stay in gear --- I'm just wondering if that is the way a 70 4-stroke evinrude(suzuki) operates... I wouldn't think so, but I hate to tear into the lower gearcase, not knowing for sure that there is a problem. Rotating the prop shaft does not solve the issue. It appears to shift in and out of forward and reverse with the engine running but still pops back into neutral when I do not manually hold the shifter in forward position. Thanks, Ron

[thataway]

Go to http://www.crowleymarine.com/johnson-evinrude/parts/53621.cfm
That should be a schematic of the shift level. There is a coil spring there part #37. If this is not the correct model number--then go to the main web site and you can find the correct model.

Larry H probably has some experience with these engines and lower units.

I believe that all of the 4 strokes were made by Suzuki, but there were Evinrude parts numbers. It should be a great engine.

[Larry H]

Sorry, I don't have any experience on the Evinrude/Suzuki 4 strokes.

[Sea Wolf]

Ron-

I can't help you from an "experienced" level, but will offer some logic:

The shift dogs, and lever shift mechanism should be self-energizing and self-locking to stay in gear.

No engineer in his right mind would design a gear shifting/changing/operating system that required cable tension to stay in gear.

If a system required continuous cable tension, it

1) could not ever be used in a manual shift mode with the lever on the side of the engine, necessary with a broken cable, and

2) major damage to the gear changing dogs would occur any time a cable broke, and the engine would also rev up into unacceptable RPM levels.

I also think some of these medium sized engines are used in a manual shift and tiller arm mode in some places in the world and in military applications.

I'm betting there aree coil springs and detent notches or cam lobes to affect this locking effect, unless it can be designed into the shift dogs themselves.

But then, this could be my night to be wrong again!!!

Joe.

[Larry H]

Joe,

In the actual Evinrude (not Suzuki) gearboxes, the shift dogs have a slight negative angle so that the thrust load pulls the dog into the gear. There is also a spring loaded set of balls (detents) in the prop shaft so that the dog stays in fwd, neutral, or reverse.

I agree that a shift dog that is only held in gear by cable tension is unworkable in practice.

[digger]

I'm in agreement with the responses. I've never seen a gearbox that needed to be "held-in" with tension from a cable either...that is why I think there is a problem. I guess I will dig in to the gears even though I hate to address the probable frozen bolts, etc that tends to thrive in outdrives and outboards in general. I don't hear any weird or bad noises, so that is a good sign. I've got much more experience in tearing apart and rebuilding engines than lower units, so I guess now I get to expand my horizons. My service manual is barely adequate even though it is oem. I usually can see the logic on how things work, but with the way the exploded views are in this manual I think I'd have to be smoking something to think I understand the inner workings...time will tell. Thank you for your input. Ron

[Sea Wolf]

Larry-

I took one of the old 2-stroke Johnson 18's gear cases apart years ago and replaced the bearings and seals, but it's been 15-20 years, and my memory of a one-time event is a bit nebulous. (!)

Thanks for the clarification! Just thought I'd tell Ron that I thought it wasn't operating as it should, logically.

Joe.

[Capt Harpoon]

That is a great engine. I bought one new about 10 years ago and put it on a new 2001 Lund Alaskan 18, where it still is today. We currently use it several times a week. It has about 2,500 hours on it and is still going strong. The only real issue I ever had was the idle air control valve icing up and triggering the alarm at air temperatures below freezing. On the advice of a good mechanic, we ignored it. Good luck getting her going.

[digger]

For those interested in what was found on the lower unit, the answer is: nothing wrong. I pulled the unit off the motor and removed the shift rod. The photo I'll attach shows the rod with a spring that either compresses or tensions when the shifter is moved...there is nothing else that can happen. However, upon removal, the detent slipped across the opening and there was no way to reassemble the lower unit without complete tear down. I had to fabricate a deep spanner socket that I could use my impact wrench on, since the spanner with a bar welded on would not move the jam nut. Once assembled and using the impact wrench, the jam came loose, and then to pull the bearing carrier I had to fab another puller to remove the carrier. Once it was out, the reverse gear could be removed, and access was available to depress the detent so the shifter could be reinstalled and the case could be reassembled. Now approximately 6 hours later, I can say -- that's the way them Suzuki engineers designed it guys. The gearcase needs cables attached to stay in gear even with the detents. Hopefully, I can get the photo up -- I am better with engines than with this new Mac computer. Ron
http://www.c-brats.com/modules.php?full=1&set_albumName=Snoopy-C&id=IMG_1800&op=modload&name=gallery&file=index&include=view_photo.php