"special" Chapman Wrench

H

Haifisch

Well-known member
Joined
Mar 7, 2019
Messages
156
Fluid Motion Model
R-31 S
Vessel Name
Pilar
Hey all, need a bit of help.

I sucked a line into my stern thruster and sheared the shear pin. I misplaced the "special wrench" that came with the boat. Any advice on the size and where I can this to remove the two bolts holding the motor to the gear box? I have a set of chapman drivers, but they they have a knob on the end that makes them too long to fit into the tiny gap.

Thanks for any advice to those who have gone before me!

John
 
Good call on the Chapman on Amazon, Gini. The mulwhark wouldn’t work for me, but maybe would work on a RT.
 
Dave, I’m curious, why wouldn’t the MulWark tool work on your Cutwater? What was the problem you encountered?

Rob
 
I have a Chapman set, but it won't work in this application. The bits have a knob protrusion on the back side that make them too long to fit in the gap between the bolts and the thruster motor assembly. The special wrench is flat on the back side. The Mulwark one looks like it might work. Once again, thanks Gini.
 
Yes, I've found the MulWark set to sometimes work where the Chapman won't, precisely because the bits sit flush in it, where in the Chapman the bit extends all the way through the wrench. Often either one will work fine. Handy to have the full set of bits that come with the MulWark. The Chapman will only work with bits that have the small little "tension" ball in the middle (which probably has an official name but I have no idea what it is). Plain bits fall right through it.

Gini
 
I believe the “special” bit customized for the Sidepower thrusters is a regular Chapman 6mm bit (with tension ball) with a ground off tip to make it shorter.

The first time I changed my thruster shear pin I found the tool I received with the boat would not fit. Upon inspection I found the bit supplied with my tool was ground slightly at an angle making it a little too long on one side. Fortunately a neighbor boater had a grinder that I used to square off the tip to make it fit.

One other challenge with the Chapman wrench is that it only ratchets in one direction. The bit has to be removed and reinserted in the opposite side of the wrench to reverse the ratchet function. In other words, once set up to loosen you cannot re-tighten without removing the tool from the hex cap screw. This can easily result in a jammed tool if one cap screw is loosened too far (perhaps even less than one turn depending on the length of the particular bit) before the back of the wrench hits the thruster housing. If this happens another 6mm wrench is needed to loosen the cap screw on the other side of the thruster to free the first tool. For this reason I now have two of these Chapman wrenches. Two wrenches also makes the removal and reinstall action go much faster as the wrench doesn’t need to be transferred side to side. An alternative is to grind down a standard 6 mm Allen key as an emergency wrench recovery tool.

Curt
 
RobMcClain":1niw2p1b said:
Dave, I’m curious, why wouldn’t the MulWark tool work on your Cutwater? What was the problem you encountered?

Rob
Click to expand...

Hi Rob,

The bit/wrench setup was still too deep to get at the back side of the stern thruster motor to get the housing off. The only one that will work for me is the Sidepower specific wrench for that one...
 
I now have two of the Sidepower supplied tools. I loosened the bolt on one side two far and had to buy the second tool to be able to recover the original wrench and also to remove the motor to replace the shear pin.

I also make my own shear pins from stainless steel weld rod or bronze weld rod.

Barry Thompson
TOUCAN, R-27 Classic
 
I joined the Loyal Order of Shear Pin Replacers this weekend. Big thanks to Dave B for the tip on having two wrenches. Following the tips from those who went before me, it was pretty straight forward and took a little over an hour. To prop up the motor while setting the bolts I placed some folded towels under it. Access was not bad, but I can't imagine doing this if I had a generator in the rear laz!
 
Haifisch":2b2zw4he said:
I joined the Loyal Order of Shear Pin Replacers this weekend. Big thanks to Dave B for the tip on having two wrenches. Following the tips from those who went before me, it was pretty straight forward and took a little over an hour. To prop up the motor while setting the bolts I placed some folded towels under it. Access was not bad, but I can't imagine doing this if I had a generator in the rear laz!
Click to expand...

good work! This post reminded that despite having two wrenches, at this moment I'm not sure where either of them are. :lol: I'm sure they are buried in the depths of my toolbag, since I haven't used them since the last shear pin replacement. I share your sentiment on access - I can't imagine having a genset and being able to get at the thruster assembly without being a contortionist!
 
Not sure Stuart. It’s a very tight tolerance on my C30 and the only thing that would work for me is the sidepower wrench. YMMV with a different boat.
 
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