Dog Clutch on Cobra-gctid810175

[CptCrunchie]

Took the boat out yesterday. When I put in forward gear, it shifts beautifully. When I put it in reverse, it's like a clunking hit-and-miss, though the prop does move the boat.

Do the same 'dogs' work for both forward and reverse?

I found this page with a description, but I'm having difficulty absorbing how it works. Obviously something slides back and forth, but how does that engage the 'dogs'?

[Download_Complete]

Sounds like a shift cable adjustment/replacement is needed.

[CptCrunchie]

"Download_Complete" post=810179 wrote:
Sounds like a shift cable adjustment/replacement is needed.

Adjustments I leave to my OMC guy. He did this once already when I first bought the boat.

As to replacing, do I replace just the cable, or the cable and casing?

[Norton_Rider]

Before you replace the cable, have the mechanic readjust the shift linkage. Make sure that this person is familiar with OMC Cobras. Also, do not use the boat until then. All it takes is a few missed shifts for the shift figs to get damaged.

[CptCrunchie]

"Norton Rider" post=810191 wrote:
Before you replace the cable, have the mechanic readjust the shift linkage. Make sure that this person is familiar with OMC Cobras. Also, do not use the boat until then. All it takes is a few missed shifts for the shift figs to get damaged.

Thanks. Chuck, my OMC guy with Olympic Marine in Port Angeles has been working on these outdrives since the late 80's. Guess I'd better take it to him and let him decide what I need.

[88fourwinns]

The Cobra uses a 2 cable system; there is one cable (remote cable) that goes from the shift control to the shift bellcrank on the engine bracket and the other one (transom shift cable) goes from the bellcrank to the transom mount were the cable moves another bellcrank in the pivot housing (the part of the transom mount that the drive bolts on to). The movement of this bellcrank moves a shift rod in the lower unit up and down and this is how F,N and R are selected.

In the lower unit there are 3 gears; the pinion, fwd and rev. The driveshaft from the upper unit always turns and the pinion is at the end of that. The fwd&rev gears are in constant mesh with the pinion and spin all the time the engine runs. In neutral both fwd&rev gears free wheel on the prop shaft. In between the fwd&rev gears is the sliding dog clutch. It has notches or dogs cast into both ends of it. The gears have corresponding notches in the inner side of each gear. The sliding dog clutch is splined to the prop shaft, when you shift it moves the clutch into engagement with whichever gear you selected. This Locks either fwd or rev to the prop shaft and that is how power is transmitted from the pinion to the prop shaft.

Problems:

Transom cable wears and gets sticky then you don't get full engagement which makes it jump out of gear and rounds off the notches.

Remote cable can slip out of adjustment and then you don't get equal stroke in fwd and rev. This can cause it to shift ok in one gear but not the other.

The other part of the system is the ESA; this is what lowers the idle speed when shifting from in gear to neutral. Due to the way the notches are cut in the gears and dog clutch, once shifted they tend to stay locked in gear. When you try to shift out of gear with a load on the prop it puts a load on the outer casing of the shift cable. This in turn causes the cable casing to flex the load lever on the engine bracket and that activates the ESA which lowers the idle briefly to 450 or so and allows the gear and dog clutch to disengage and this is how the gearcase shifts to neutral.

[desuch]

Very good advice I own a cobra and are a good outdrive but it doesn't take many mishaps with shifting and grinding to wipe out the gears so make sure your mechanic is fimilar with the omc ,been there and now have a new one with one to be have the forward gears replaced

[Chief_Alen]

Give this a peek, choose the section you want to read.

http://www.crowleymarine.com/support/omc-tech-articles.html

[2850Bounty]

"CptCrunchie" post=810175 wrote:
.....................

Do the same 'dogs' work for both forward and reverse?

[color]blue wrote:
Short answer, NO!

You will see three gears within the lower gear unit.

One "drive" gear and two "driven" gears.

Each driven gear incorporates dog clutch engagement teeth just inside of the hypoid gear teeth.

The sliding sleeve (the part that creates the engagement) incorporates corresponding dog clutch engagement teeth at either end.

When the sliding sleeve is moved foward (causing the dog clutch teeth to engage), you will have FWD propeller motion.

Likewise for REV when the sliding sleeve is moved AFT.

I agree with the guys who have suggested having the adjustment made!

Whether OMC Cobra or Merc A drive, the Dog Clutch principle is very much the same. [/color]

[attachment]36719 wrote:
Dog Clutch dove tail cut 2C.jpg[/attachment]

[attachment]36720 wrote:
Dog Clutch image how it works 3 .jpg[/attachment]


Attached files

[CptCrunchie]

"2850Bounty" post=810311 wrote:
[color]blue wrote:
You will see three gears within the lower gear unit.

One "drive" gear and two "driven" gears.

Each driven gear incorporates dog clutch engagement teeth just inside of the hypoid gear teeth.

The sliding sleeve (the part that creates the engagement) incorporates corresponding dog clutch engagement teeth at either end.

When the sliding sleeve is moved foward (causing the dog clutch teeth to engage), you will have FWD propeller motion.

Likewise for REV when the sliding sleeve is moved AFT.

I agree with the guys who have suggested having the adjustment made!

Whether OMC Cobra or Merc A drive, the Dog Clutch principle is very much the same. [/color]

Excellent, Rick. Thank you. I've printed the photos. Great description. I'm still going to let my mechanic adjust it, but at least I now know what he'll be doing.

[Ruffryder]

Easily explained here...

https://youtu.be/vuAcrDFvApA