CD 31 Re-powering

[Bill Sonntag]

CD31 Re-powering
July 2005

This is a description of some lessons learned during motor propulsion re-fit/re-power job done by a competent yard on a 21 year old, Cape Dory 31. This was prepared for the boat’s maintenance file but may be of some interest to those searching this subject for re-powering options..

Sterntube, Cutlass Bearing, Stuffing Box

The yard was surprised by the installation technique used by the hull manufacturer (assuming original builder configuration) for the fiberglass sterntube. The sterntube proved to be the source of a multi-year chronic minor leak turned worrisome this Spring. Just before being hauled for this maintenance, the boat was taking on about 3-4” per hour, a constant, solid trickle running or not. The sterntube was “puttied-in” with no resin, glassing etc. There are numerous other posts on the Cape Dory Message Board regarding this maintenance work/build item. The yard removed then re-inserted the sterntube with resin bedding and fiberglass roving around the exterior aperture. then replaced the cutlass bearing. Based on this experience, sterntube soundness should be a check point for any owner of this series of boats. Again, see discussion posts regarding which models used fiberglass or bronze sterntubes.

The bronze prop shaft was worn, noticeably grooved at the cutlass bearing and the stuffing box contact points. Replacement was recommended, a new stainless steel shaft has been fitted. New cotter pin locked prop nut was fitted that includes a sacrificial zinc anode.

Switching to a “drippless” Teflon/graphite (i.e. PYI) shaft seal was considered. The original stuffing box was cleaned and re-installed based on 21 years of reliable operation, review of posts here the Cape Dory Message Board, good condition of the Spartan bronze stuffing box, advice of the yard that repacking with Teflon impregnated packing material would work fine and general accessibility of the stuffing box for tightening,. A new rubber flex tube from sterntube to stuffing box with new clamps was installed.

Engine Replacement

The original Universal M25 replacement with a Universal/Westerbeke M25 XPB was as advertised, a close as can be had to an exact swap. Some rewiring of the engine control panel electrical harness was necessary. The original “deluxe” control panel was in good shape so it was retained. The transmission cable attachment was modified to result in forward, reverse selection lever-action corresponding with forward and reverse gear. It was also necessary to fabricate a new water injection riser from the water-pot exhaust system. The old one was deemed unsatisfactory due to restricted tube diameter and due to carbon build-up. The other installation complication came from work on sterntube etc described above. The engine/shaft alignment was affected by the new sterntube installation requiring extra labor to shim rear motor mounts.

Operation Orientation, Shake-down

Extra time was taken to understand and heed the engine break-in requirements/recommendations. The operation of the reset button for the fuel lift pump was explained. The self-bleeding nature of the fuel system was explained with the lift pump capable of expelling all minor air intrusion due to routine filter changes etc without fuel system line bleeding.

The engine has been run well below the max RPM and top range of cruising RPM for the shakedown cruise. It was recommended that 2200 be the top operating range for the first 50 hours, with the RPMs consistently varied during any long runs. The engine has been operated at 2000, 2200, 1800 etc for the first 20 hours. As with the old engine, access to the transmission fluid level dipstick is limited as is access to the heat exchanger pencil zinc. They must be accessed from rear via the cockpit lockers.

Engine Operating Impressions

The difference between the old engine capabilities and the new performance is significant. The engine jumps to operation at about half a starting crank and is considerably quieter at both idle and cruising RMP ranges. The boat moves through the water much better especially in a head sea and breeze. A brief run through a very choppy Chesapeake head sea showed much better forward progress. Overall speed has increased at low RPM (a completely faired and re-painted bottom also helps). A short run in calm water at 2500 RPM put the boat well over 6 knots. The original builder supplied 2-bladed “sailor” propeller was retained. The stuffing box needs a turn taken on the packing nut. It has been leaking some water, but has settled-in after 20 hours of operation. The engine has operated exactly at or just below it’s 185 F thermostat setting in warm Chesapeake waters.

Finally, and importantly, the shake-down cruise included two days of superb Chesapeake summer sailing. A clean bottom set her up like a new filly, flying down the Bay on a close reach surprising some very much larger boats as she drew away toward Bloody Point and beyond.....

Happy Sailing

Bill Sonntag
Surprise - CD31 Hull No. 30

[mike connell]

BILL, I MAY BE FACING REPOWERING MY 31 ALSO. DID YOU LOOK AT OTHER ENGINES,YANMAR ECT. ALSO WHAT KIND OF $?

[Bill Sonntag]

Mike:

I went with the recommendation of the yard doing the work. They specialize in Westerbeke/Universal installations and it was the closest to a "swap-out". The engine cost was $7500. I had looked into Yanmars (I had a dependable but very rough and noisy 2 cylinder on a Tartan 28) and read the posts on the Beta engines on this site. Nothing I saw suggested great advantages over the Westerbeke/Universal. I would note that the difference in overall level of technology for the current Westerbeke/Universal engines over the early Universal diesels is significant.

Bill Sonntag

[mike connell]

Bill thanks for the info, my m25 is being pulled as we speak, do not know if it can be fixed,will keep you posted. My CD 27 that is for sale has the 2 cyl. F/W cooled Westerbek and its been perfect.
FAIR WINDS MIKE

[mike connell]

BILL IF POSSIBLE, CALL MY V/M 1 800 544 0429 EX 2088,LV YOUR # AND I WILL CALL YOU. IT LOOKS LIKE A NEW DIESL MAY BE IN MY FUTURE. IHAVE SOME ??? ON FIT WITH A NEW TRANSMISION.