Thread: Ramsay Rebel Dog Clutch Vibration

Thanks Tinman. No the shaft is not spinning when out of gear, I just mean it vibrates without spinning. It's easy to pull the prop shaft and pull the dog clutch off, so I'll do that and remove the dog clutch input shaft and bearing. I check the input shaft and bearing and see what that tells me. I've attached a photo of the shaft bearing in the dog cluch housing.

No not a damper plate set up. It has a fixed dog that bolts on the end of the crank. The fixed (nose) dog has a spigot bush which the dog inpit shaft fit in to. There is a slider dog that slides on the plines and moves in to engage the nose dog when you put it in gear. I think this is the same as most dog clutches. I can send pics if you want.
Ta

my clinker used to do it, people replace shaft and not skeg, or skeg wares out, its also possible to get vibration from a rooted engine mount, or it possible your balancer is fukd.

G'day, I have a ramsey rebel boat with the same vibration problem as you have described, I have a new shaft, new prop and skeg fitted and have adjusted engine as close as i can. Just wondering what you found with your problem, wether it was in the clutch or an alignment issue. Any help would be greatly appreciated.

Originally Posted by Rouser308

Hi All, I got such good help with my last problem I'm back again. Just to recap, I have a Ramsay Rebel 1972 model with a 308 flywheel driven dog clutch. I have a vibration from about 1200-1800 rpm (after that it smooths out). It does it when in and out of gear - yes out of gear when just running on the hose in the back yard. I can see the prop shaft vibrating. What could cause this? Could it be the dog clutch bearing or perhaps a bend in the dog clutch shaft? I would think they are both original items. Ta.

Mate have you looked at you flex plate at all to make sure it still isnt the problem cause said it does it when not in gear aswell just a thought.

Hi Guys, thanks for the suggestions so far. I have confirmed the dog clutch shaft is not bent and I have a new harmonic balancer, dog clutch spiggot bush and dog clutch bearing. I'm now going to check out the flex plate. This does mean removing the bell housing and lifting the back of the engine (as the bell housing also has the rear engine mounts as part of it).

Just so I have it clear what the problem is, its a prop shaft vibration that is there both when it is spinning and when it is not spinning. My thinking is that there must be something out of line or bent either in the dog clutch or further forward in the engine.

Suggestions so far:
Prop - no as it does it when stationary
Prop shaft - no as it does it when stationary
Dog clutch shaft - checked and OK
Dog clutch bearing - replaced

Happy to hear any others...ta
Dog clutch spiggot bush - replaced
Dog clutch dogs - replaced
Harmonic balancer - replaced

Originally Posted by Rouser308

Just so I have it clear what the problem is, its a prop shaft vibration that is there both when it is spinning and when it is not spinning. My thinking is that there must be something out of line or bent either in the dog clutch or further forward in the engine.

Ok I'm confused!! I'm not sure how the prop shaft can vibrate when it's not spinning unless there is a vibration from the engine and causing everything to vibrate? I thought it was established earlier that the vibration was coming from the engine because it was suggested to disconnect the prop shaft and try it again, was this done? You had also removed the dog clutch assembly from the bell housing for inspection, was the vibration rechecked at this point? If the vibration is still there then, you can eliminate prop shaft, dog clutch and alignment of the two. I have eagerly been awaiting whether the flex plate was the source of the vibration, as this is also what I would be checking next. A mate of mine had the same engine with the same issue and it turned out to be a cracked crank. I apologise in advance if I have completely misunderstood the symptoms and diagnosis. I really hope you get it sorted out.

Hi ski351, you are spot on. Vib is there when spinning and not spinning. That is why I was thinking dog clutch shaft (as crank turns around the stationary dog clutch shaft it causes the vib). In the fault finding, I took out the fixed dog and put the clutch assy and propshaft back together and the vib was gone. Now that I have checked the clutch shaft I think it must be something further forward ... flex plate, crank?? mains bolt come loose???

I can see the prop shaft vibrating at the log seal...it stops vibrating at 2000rpm?!?

Ok mate, I think I'm with you now. I had a flywheel driven dog clutch on my 351C years ago and looking at your pics it's identical, so I can visualise yours perfectly!

Here are my questions now:
1. Your fixed dog (the one bolted to the crank), is that gear all one piece, in other words if you chip those teeth beyond repair do you have to throw the whole thing away? or... does that gear bolt separately (3 countersunk bolts) onto a "boss" that then bolts onto the crank?
Mine was all one piece and it had been re-welded many times beyond repair so I considered the type with the replaceable gear.

2. You removed the fixed dog, so the flexplate was bolted to the crank by itself and the vibration disappeared, right??
If this is correct the flexplate is not your problem.

I'm thinking along the lines that your fixed dog is not running true with the crank, like it has radial run-out. If it does, because the dog clutch shaft locates in a brass? spigot in the fixed dog it could be causing the shaft to run-out/wobble at the prop shaft flange.

You can check this by simply looking at the prop shaft flange (prop shaft unbolted) and see if it wobbles with the engine running and dog clutch disengaged.

I had very similar vibration issues with the drive flanges between my prop shaft and the v-drive and it would only be there between a certain rev range. It was so bad the prop shaft would bend like a banana and hit the hull where it passes thru the hole at the log base!! The problem was run-out!

I'm determined to get to the bottom of yours too!!