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S&S Swan Maintenance - New Drive train for 43
07 May 2013 - 14:49
Join Date: 15 April 2011
Posts: 395

New Drive train for 43

Dear All,

In a recent forum post the Professor provided an eloquent and informative description of the reasons why the Perkins 4.108 should be set up with a reduction gear and propeller to run at 3000 RPMS.  

My boat, Mabel's Casse Tete 43 003 was repowered in 1986 with a Perkins 4.108; I believe the original rudder was kept, but modified through grinding off approximately 1 inch in diameter and the gear box reduction was 1.52:1.  In practice, I was able to run the engine in gear in flat water up to 2100 or possibly 2200 RPMs; I posed this problem to the Professor.

In subsequent correspondences, we have decided ( I use WE because I feel like I have a partner in this and other projects and I am careful to head the Professor's advice) to:  replace the gearbox with a 2.57:1 rebuilt velvet drive gearbox; the 16"(reads 17" but measures 16") two-bladed propeller with a three-bladed Flexofold 19" folding prop with a 13 1/2" pitch; the 1" shaft with an aquamet 22 shaft - diameter to be determined; coupler to be determined; stuffing box to be determined; shaft-log to be determined.  The Professor has kindly and graciously made all of the calculations and, more importantly, has given me the confidence to move ahead with this project!

While the gearbox is off, I plan to replace the rear oil seal.

Finally, the strut and boss which supports the shaft just before the prop and houses the cutlass bearing has been modified and needs to come out to be repaired!

I will post pictures as I go along!

This is a very exciting project for me.  As usual, most of what I will be doing, with my sons, of course, is new work so I expect to make mistakes and to ask some dumb questions, but the idea of having a power plant and drive-train that really works well is important.  I have been in situations when the engine becomes a vital piece of safety equipment!  Those times, believe it or not, were mostly on anchor in tight anchorages or stern-to at docks when significant wind and wave action forced me to drive into the weather.

Chris  Mabel's Casse Tete  43  003


13 May 2013 - 17:00
Join Date: 15 April 2011
Posts: 395

Dear All,

I visited my boat this weekend with the intention of removing:  propeller; shaft; and gearbox.  I was partially successful.  I was able to diconnect the coupler and unbolt and remove the gearbox.  However, that's when the fun began!  I had no idea how heavy the gearbox is.  No son this weekend to help.  The floor just aft of the coupler had been modified and compromised - I dropped the gearbox on it from about 3 inches and it crakced!

I had thought about replacing this floor and i am glad it happed now.

To get access to the back of the engine and the gearbox I had to remove the cabinet directly aft of the engine compartment along with the water heater.

Question:  what is this cabinet used for on your boats?  It seems a strange place for a water heater and certainly limits access.  Where are your water heaters located?

I spoke with Trans Atlantic Diesel today; they have a rebuilt 2.57:1 velet drive ready for me.  It will cost $1150 with the exchange of my current gearbox.  Not too bad!

Not many pictures since I had my hands full!

Chris Mabel's Casse Tete  43/003

water heater and back of engine

16 May 2013 - 02:03
Join Date: 20 February 2007
Posts: 119


I had to move my engine up and forward about 6 inches to get my transmission out. Yes the transmission case with reductinn gearing is very heavy probably weighs something over 90 pounds.

I spent nearly half a day with a good friend trying to wrestle the gearbox out but was not successful. After conceding to my friend`s original suggestion of moving the engine forward a few inches the transmission came out no problem.

The lesson is don`t try to get the transmission out of a Swan 43 without first moving the engine. The whole process of disconnecting the exhaust system and engine mounts and moving the engine took about an hour, compared to wrestling with the lump of steel for over half a day ending in defeat.

I found that the engine was installed with enough slack in most of the ancillaries such as flexible fuel lines, battery cables, etc that you do not need to disconnect everything. We put a 4x4 across the top of companion way hatch opening and used a small chain hoist to lift the engine off it`s mounts and then slid the engine forward about 4-6 inches.

The transmission can then be lifted up and forward of the floor beam that prevents it from coming out when the engine is in place. I took out the transmission and reduction gearing case as a unit.

We leaned a long ladder against the hull and used it as a ramp to slowly slide the transmission down to the ground (my mast was not in the boat at the time so could not improvise a lifting system using the boom.

Re-assembly is reverse of dis-assembly. Obviously make sure you re-align the engine to the shaft using the engine bed adjusters.

I did not replace the rear oil seal of the Perkins at the time I did my transmission and regret not having done so as I now have a slow leak there.

One helpful tool I found for getting to adjusting the bolts that secure the engine mounts to the engine beds was a box wrench with a cut down handle that I made from an old wrench.

Good luck with this project. Let me know if there are any other questions.



17 May 2013 - 13:21
Join Date: 15 April 2011
Posts: 395

Dear Hiro,

Thank you for all the advice.  Your comments are always welcomed, appreciated and helpful!

Although one can see that the gearbox is large, I had experience with a Hurth gearbox that skewed my thinking; the older I get the more this seems to happen!  Anyway, that gearbox was attached to a marinized 85 hp Mercedes Benz "Nanni Diesel" truck engine; the gearbox weighed about 30 pounds.  After cutting many of the nuts and bolts that held the engine in place, it came off easily and I put it under my arm and off I went; not so with this gearbox. 

Fortunately, I did remove everything behind the engine, including cabinet as mentioned, so I had good access.  As you know, however, without the sole in place, the slope of the hull, with a  little ATF added, makes for a slippery foot hold. 

I did not have to move the engine and the gear box is out and sitting across the hull just above the driveshaft.  I have my son and a friend coming with me on Saturday so I think we will be able to remove it - keep you fingers crossed!

Only question I have is:  what do you use the cabinet for that is located just above the gearbox, behind the engine?  Wet locker?

With everything out, I am hoping that I can relocated the new vetus muffler inside this cabinet.  Right now, if it stays where it is, I will need to modify the sole and I would prefer to avoid this for several reasons.

Thanks again,


18 May 2013 - 02:18
Join Date: 20 February 2007
Posts: 119

Hi Chris:

On my 43 the space above the transmission area is where the engine instrument panel is located. Also a small alcohol tank for the Luke alcohol stove and the vertical muffler is also in this area.(see the swan 43 maintenance section for photo of muffler).
I am not sure how much of this is original to the boat.



19 May 2013 - 14:52
Join Date: 15 April 2011
Posts: 395

Dear Hiro,

Thank you.  I just looked at the line drqwings for the 43 and see that the closet is indeed originally intended for "oilskins."  This seems a good use but I wonder where I will place the water heater.  For now, the water heater is out as is the be swapped on Tuesday!

With warm regards,


23 May 2013 - 14:53
Join Date: 15 April 2011
Posts: 395

Dear All,

I have the "new" rebuilt 2.57:1 transmission/reduction gear ( a little confused about the terminology) for the Perkins 4.108.  I dropped off the "core" at Transatlantic Diesel and picked up the new one.  I was impressed with the magnitude of the operation; the store/warehouse, located in southeaster VA, USA in the middle of nowhere, had about 15 engines rebuilt, wrapped and on pallets, ready for delivery.

The mechanic who apparently rebuilds the engines and transmissions spent a lot of time speaking with me and provided great insight for my related projects; rear seal and oil pans seals. 

if you are looking for a place to purchase perkins parts, I like this group.  I have been dong business with them for 2 year now and have been very happy.


22 May 2017 - 17:36
Join Date: 15 April 2011
Posts: 395

Dear All,

I have been on a very long hiatus from boat work or, at least, significnat boat work.  I see from the date of this post that it's been 4 years since I purchased the rebuilt transmission!  

Here are pictures of the installation; i could not have done it without the help of my younger son, Alex, in the picture.  Alas, he is headed back to school in a few days so I'll be back to my lonesome again.

Installation notes:  We used the main halyard to lift the transmission onto the deck; one at the halyard and one with a guideline.  The velvet drive is extremely heavy and unwieldly and one needs a clear mind and patience to do the job correctly - maybe that's why it took me 4 years!  

That method was successful and easy.  We lowered the transmission through the companionway entrance and left it hanging above the engine.  I recently removed part of the plywood bulkhead directly behind the engine which made locating the tranmission in its place behind the engine very easy.

Still hanging on the halyard, we positioned the transmission precisely and  then fitted the transmission input shaft into the new pressure plate.  This process took a lot of coaxing, intense discussion, some kicking of cabinets, and, finally, Alex to get it just right!  Once in, we bolted it in 6 places and left!

Chris, Mabel's Casse Tete  003/43

22 May 2017 - 17:38
Join Date: 15 April 2011
Posts: 395

It appears that my photos are rotated 90 degrees but I think you may still see the results.


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