Prop Alignment & Engine touching Hull

[miquelkumar]

While attempting to align the prop on my CD28 M18 engine I noticed that a protrusion or flange on the transmission is not only touching the hull but seems to have "dug into" the hull on the starboard side. It occurs at the turn of the bilge so I assume the glass is thick at this point. I have raised the engine about 6 full turns on the mounting bolts but it hasn't cleared the hull yet. I'm sure if I do raise the engine enough to clear the hull the alignment will be non-existant. Anyone experienced this? Did CD grind out the glass to accommodate the engine?

Thanks for your input.
MK
Joe Toe - CD 28
San Diego

[Matt Cawthorne]

On my CD36 the clearance is minimal. I think that the drilling of the shaft was probably imprecise from boat to boat. In my case the engine support that runs from the engine to the rubber mount was against the engine bed. I chopped a piece of that support away.

I have often contemplated the possible solutions. I have never measured the clearance of the prop to the top and bottom of the aperature. Check the alignment first. If the engine is too close to the hull or hitting when the shaft is aligned, then look to the mounts. Are the mounts bottomed? If not, then you could grind the hull a bit and then if you were concerned about the thickness of the hull you could add some back to the outside. If the mounts are bottomed then you could modify the engine supports and grind away the hull. Perhaps a far better solution would be plug and re-drill the hull where the bearing support fits. Seems like a lot of work, but that is the type of project that I would likely take on because I am a tad obsessive.

So here is a bit of a brainstorm. make a dummy shaft that mounts in your shaft coupling, but is turned down to 1/4 inch where it progresses through the hull. Remove the shaft bearing support and stuffing box. sand the opening in the hull thoroughly for a good bond. Buy a piece of G-10 or G-11 epoxy impregnated fiberglass cloth conduit that has a fairly thick wall and turn down the outside to fit in the exiting hole in the boat. Bond it in place. Put a layer of wax on the dummy shaft, mount it on the coupling and raise the engine on the mounts until it just touches the upper side of the new fiberglass liner or the thickness of the liner, which ever is less. It will not be concentric with the liner, but that is good. Squish in a pile of epoxy and fiberglass mixture into the tube. After it is cured, remove the dummy shaft by whatever means is necessary. You will now have a pilot hole to use for drilling out the back of the boat for the new bearing support that lines up with the engine. Have a machine shop make up a drill with a long, non-sharpened pilot. You may have to do an eyeball sharpening of the working part of the drill. Drill it out. Bond/bolt in the new bearing support and stuffing box.

You didn't have anything else to do, did you?


Good luck,
Matt

[Matt Cawthorne]

A hole saw might just work for the 'piloted drill'. Most hole saws have a pilot drill and you could simply put a piece of plain rod in place of it to keep the drill on target. Once you bottom out the saw you would have to chisel out the core or drill it out with some sort of a smaller diameter rough drill.

[miquelkumar]

Wow, that's more than I was ever thinking, but I do appreciate the input. You are right, I don't have anything better to do but because of that I don't have any $$ to do anything. I would consider re-powering since the cost to haul and store at the yard for that job would probably be a wash and the M18 is getting old.
An interesting thing I found was with the motor raised I could still get the coupling to connect and it still rotated fairly easy. But at one point in the rotation the shaft would bind a little. When I continued the rotation through the binding (about 15 degrees) the entire transmission and motor would shift a little to port and then back. I'm guessing the motor wants to be shifted to port or the shaft is bent. My next move is to try and shift the motor to port a little which may fix the problem(s). I would consider replacing the stuffing box and shaft but that too requires hauling.

I will be investigating more on Monday. I bet I have spent more time lying on my back and sides under the cockpit than in the berths. In fact, I have the whole area under there set up like a berth complete with mattress, pictures of the family, cup holder and speakers. Good times!!!

Thanks again, Mike

[Matt Cawthorne]

First you need to see if there is play in the shaft in the cutlass bearing. If you have any binding at all, then you should not run the engine that way. Engine alignment is achieved by disconnecting the coupling and sliding the shaft slightly back. If you have an isolation donut then remove it. Slide the shaft forward again and check that the coupling halves slide together with little or no force. Once they are together, check that the two faces are parallel with a feeler gauge. As I recall, you are looking for the left and right sides to be within .002 inches of one another. Same for top to bottom.

Re-powering is far more expensive that what I described. If you do replace it you will still be stuck with the same shaft problem.


Regards,
Matt

[miquelkumar]

I got lucky! A local marine engine shop had the transmission sitting on their counter used as a display (cut-away to see the guts) that showed the protrusion can be removed. Probably part of the casting process. I cut it off and have adjusted the alignment both vertically and side to side. I think I have it. This is the third time I've tried to align. Due to the hull configuration of the CD28 there's no room for a adult hand to feel the bottom of the coupling so I'm feeling the three points and rotating until there it runs smooth. Not easily done alone.
I really wish they would have designed the hull with a wider bilge. I have a set of packing nut wrenches I bought when I had my 25D and can't use them on the packing assembly on the 28.

Thanks for your ideas.