Sloppy shifting, or another worn dog?

I have a 57 Evinrude Big Twin 35hp with lower unit in the shop awaiting a NOS clutch dog. In the meantime, I installed the lower unit from a 56 Evinrude Lark 30hp because it appears an exact match to the Big Twin lower unit. Took the boat to the lake today and got the Big Twin tuned on the water, adjusted the control cable for the shifter and generally had a good time.
The boat is an early 60's Texas Maid 15 ft. ski boat with twin outboards (not matched); a Johnson FD-11 18 hp on the starboard side and the Big Twin on the port side. The motors are about 15-17 inches apart on the transom.
This appears a good combination, but I still had a shifting problem with the Big Twin with the Lark lower unit. It goes into gear and runs out nicely until a few minutes after attaining WOT...then it jumps out of gear. Now I haven't looked inside the Lark lower unit, so its clutch dog may be as gnarly as the Big Twin lower unit in the shop. Just wondering...any chance there is excessive slop in the shift mechanism up top? How would I check that?
Want to make sure the Big Twin is shifting well while I have its lower unit in to replace the clutch dog. When it jumps out of gear, I can throttle back, shift into N, then into F and it sometimes re-engages...but sometimes not. Even when it's in gear, the Big Twin doesn't seem to be pulling/pushing its weight as well as the smaller Johnson...which is a real champ. Both these outboards have been converted from short shaft to long shaft due to the boat's deeper transom. Any educated guesses on whether I have the outboards spaced too close...could the smaller Johnson be robbing water from the Big Twin's prop/gear case?
Sorry for the long post, never run twin outboards before so this is all trial and error.
It's a sweet combination though, they make a nice hum at speed and the old Texas Maid corners nicely. I was making 20 mph according to the old worn speedo with both outboards trimmed all the way in, and 25 mph with them trimmed one notch out. Turned a few heads, even from the Jet Ski/Flea crowd. Thanks in advance for any input.

Re: Sloppy shifting, or another worn dog?

check the linkage at the top and make sure it is engaging in the slot like it should. It might be on the edge and popping out that way.

Re: Sloppy shifting, or another worn dog?

The shift linkage has to be in proper adjustment, this is done at the shift handle on the engine. Do you have a manual? With the access plate off where the shift linkage connects in the exhuast housing, grasp the shift rod with a needle nose pliers. If you can move the shift handle, without movement of the shift rod, the linkage is worn under the power head. This must be corrected to get proper throw for full gear engagement for both forward, and reverse.

Re: Sloppy shifting, or another worn dog?

I checked the shift lever when I adjusted the shifter cable. It is seating well in the linkage slot in F and N. Stays in the F slot when it jumps out of gear. After considering it awhile, I'm wondering if I have some slop at the top of the shift shaft, where it connects to the shift lever...or in the long shift shaft connector. I guess only more trial and error will tell. Thanks for the input.

Re: Sloppy shifting, or another worn dog?

You are describing classic symptoms of a worn clutch dog/forward gear. Wont know till you pull her and see though I guess.

BTW, neat combination! I would love to own a mahogony boat one day with a couple of Golden Johnson Javelins on the transom.

Re: Sloppy shifting, or another worn dog?

Thanks R. Johnson. I was wondering about that. I'll check it out tomorrow...sounds like a good July 4 chore. Is the linkage under the powerhead hard to replace?

Re: Sloppy shifting, or another worn dog?

No! it is not really hard to replace, as all you have to do is disconnect the throttle tower shaft, and fuel line. Then the bottom bolts', and nuts' around the bottom of the power head, exhaust housing assembley, then it will lift off. If the upper shift linkage will not come into sync, you will just keep knocking out clutch dogs, as they will not go into full engagement , or be securely held in engagment.

Re: Sloppy shifting, or another worn dog?

Thanks for the info. I'll check it out and post back with what I find.

Re: Sloppy shifting, or another worn dog?

Well after cleaning up the boat today after yesterday's foray onto the lake, I discovered some slop in the Big Twin shift lever. I removed the side cover plate in the exhaust tower, held the shift rod with a needle nose pliers and discovered 1/4 to 3/8ths inch of slop in the lever...especially in Reverse. Thanks to R. Johnson for the info and how to diagnose this. Guess the next step is to haul the Big Twin into the shop, pull the power head and replace the shift linkage. Hope the parts aren't too hard to find.

Re: Sloppy shifting, or another worn dog?

Bump

Re: Sloppy shifting, or another worn dog?

I might have some parts, but I would have to check. I have a leg for one, but don't know what parts are there in it still.

Re: Sloppy shifting, or another worn dog?

Did some poring over my Johnson master service manual today and discovered a procedure for adjusting the shift lever to tighten it up. Did this: disconnected the cable and shifted lever into F; loosened the two anchor bolts that hold the lever tight onto the shaft; raised the bell crank behind the lever up tight, then back just a hair; rotated the prop to make sure the dog is engaging the gears firmly; held the shift lever tight and tightened the two anchor bolts. This reduced the slop in the shift lever considerably. May also replace the spring that holds the shift bar in place for the shift lever to engage. Takes some effort on the Johnson 18 hp to move that bar, but less effort on the Big Twin. Maybe a new spring will improve the situation. If not, may need to check the shift mechanism/collar under the powerhead.