Resolved - 1963 75hp Selectric Slipping

[F_R]

OK, reading from another manual, it calls Perfect Seal No.4 a "thread sealant". Take it for whatever it's worth.

 

[yorab]

Just put top and bottom halves together. Now I'm getting 9.0 ohms across the forward coil. Anybody know if that's too far off from the spec of 8.0 ohms?

 

[yorab]

Well, I pulled it back apart. The forward coil resistance as measured across the lead at the lower case and the case body is 8.1 to 8.2 ohms. The resistance of the cable that runs from the lower case up through the upper case is 0.7. I guess that adding the resistance and allowing a slight connection resistance gets me to 9.0 ohms.

I understand that these cables are hard to find so I'd like to not replace if possible. However, I'm not sure if this is going to cut it. Does anybody have experience with these units performing out of spec?

 

[F_R]

Have to wonder why the resistance in the cable (?)

 

[yorab]

Yeah, probably beginning to break somewhere inside the heavy thermal insulation that runs up through there. If I knew of a source, and could get the harness for a reasonable price, and I could figure out how to replace it (no mention in the service manual), then I'd go ahead and get it.

But most of those things are a negative at this point so I think I'll just button it up and experiment. Maybe the system will operate just fine showing the resistance numbers that I have. I used some Emory cloth to clean up all the knife connectors and now the resistance is around 0.4 ohms in the cable, giving me 8.6 to 8.7 ohms for the forward coil.

 

[yorab]

I was playing around with this again and I connected the forward coil lead to the harness. Although the upper and lower cases were not bolted together, there was an electrical connection between the gearcase stud and the lower pinion bearing (see pic). The resistance from the upper end of the harness to the upper case body was steady at 8.1 ohms. Same if I measured from the upper end of the harness to the lower case body.



I think that my problem lies in the lower end of the harness. The leads are long so that the knife connectors can be disconnected/connected during disassembly/assembly. That excess wire needs to be tucked up into the cavity in the upper case (see pic). The wires are not very flexible anymore, so they sort of kink as the wires zig zag back and forth in a "Z" shape in order to fit into that cavity. I think that perhaps the strands are beginning to break inside the insulation there. The resistance is fine when the wires are allowed to straighten out without any kinks, like in my first pic.



If the problem is indeed in the lower harness, it's a tough problem because it's so hard to do anything with the harness inside that cavity due to space constraints.

 

[jimmbo]

Removal/install is just brute force, gripping on the heavy insulation(not the wires) and pull. A bit of dish soap as a lube will do wonders for installing. I guess with tension on the harness some soap and water can be applied to seep between the harness and housing to ease removal. Start shopping for a new harness. I doubt OMC ever envisioned these would still be running 55 yrs later

iboats does sell a terminal kit, new connectors I assume.
http://www.iboats.com/TERMINAL-SLEEVE/dm/cart_id.112449822--session_id.975515617--view_id.1484725
Is there enough slack to install a new connector before the 'kink' and still make the connection?

 

[yorab]

All wrapped up.

I'd like to replace the harness, but $150ish is a bit to high for now, so I was determined to make the old one work.

​I realized that the knife connectors between the lower and upper gear cases weren't very tight when clasped and that the insulating sleeve that covers the connection was stretched out. Therefore, when the leads were crammed into the cavity in the upper gear case, I'm guessing that the weakest point may have given in, which may have been the knife disconnects. Because there was plenty of room inside the stretched sleeves, the connectors could open quite a bit, though they couldn't completely separate. If the connectors did open up, the not-so-tight connection may have led to increased resistance.

​Therefore, I replaced the insulating sleeves with NOS that I had. Wow, that was a pain. The hole in the ends of the sleeves were so tiny that it was extremely difficult to stretch over the knife connectors even with lube. After many failed attempts to get those sleeves on and even more curse words, I cut notches in the ends of the sleeves to enlarge the holes. Then I was able to slide them on. The ID in the middle of the sleeves was still small, so it will help to hold the knife connectors closed together because there just isn't room inside the sleeves for the knife disconnects to make the scissors-action movement and loosen up. I also used pliers to squeeze the connectors together once clasped. ​After reassembly, I was getting 8.6 and 8.5 ohms across the forward circuit and reverse circuit respectively.

​I still get the feeling that the leads are not in the best condition, but it seems that 8.6 and 8.5 ohms is sufficient for good operation. I took the boat out and worked it hard, but there was no slipping under any conditions.

 

[Willyclay]

I took the boat out and worked it hard, but there was no slipping under any conditions.

Attaboy, I knew you could do this!

 

[yorab]

So what was the original problem that caused the slipping? Was it the cables or the connectors? Probably neither.

​The gearcase is designed to take into account the fact that the greater percentage of motor operation is in forward gear. Because of this, the forward drive gear rides on a bushing and the reverse drive gear rides on a needle bearing. The forward clutch hub is also knurled for the same reason. The bushing must be used with the knurled hub and the needle bearing with the smooth hub. Did I mix these up? Of course not! Sheesh, that would be a rookie mistake.

​It's also important that the complete forward clutch hub assembly (knurled hub, gear, spring, bushing) be installed at the tapered front end of the gearcase cone and the reverse clutch assembly be installed back near the gearcase head.

​Did I mix these up? [hands in pockets, looks down at the ground, kicks some gravel around a bit, refuses to answer the question]. Oy, I did. What a rookie mistake! After reading about this in the service manual and reading multiple warnings on the forum about doing this, I did it anyway during my original rebuild. It was a whole lot of extra work that I really didn't need. A good lesson for somebody else doing this for the first time.

 

[jimmbo]

Did you check the oil after you ran it to confirm you got the water leak fixed?

 

[yorab]

I didn't get a chance. I'll try to do that next weekend. However, after putting it back together, it held 10 psi and 10 in hg for at least 20 minutes.