CD27 repower question

[John D.]

I'm in the middle of repowering my CD27. (It is taking much longer than it should have, but that's another story.)

My question is about the engine mounts and beds. I'm having a BETA BZ482 installed to replace a YSM8. The BETA "certified" mechanic is planning to install the front and rear mounts both on the front mounting bed. The rear bed will go unused. I have two concerns, and would be grateful for any comments.

Concern #1 - there is very little depth at the back of the front mounting bed. Is there enough material between the drip pan and the hull to tap bolts into?

Concern #2 - the front-to-back distance between the mounts will be very short. Can that cause any problems, such as excess vibration?

Any thoughts would be welcome.

[Parfait's Provider]

I am having a hard time picturing what is proposed but it sounds as if the mechanic is suggesting the the engine can be balanced on the forward bed?

I think there are two problems with this.

1) The transmission shaft will be acting as a support for the engine which will lead to transmission problems, stuffing box problems, cutless bearing problems, and who knows what else.

2) The torque on the forward bed will tend to rip the bed out of the hull which, depending on what turns out to be the weakest link, will simply further misalign the engine and shaft, tear up the mounts, rip out the bed, or sink the boat.

The output shaft af any transmission is not intended to be a support foir the engine. I think you need a different installer. Good ones aren't cheap, but they have better ideas than what is proposed. and will save you a lot of money.

[Bill Goldsmith]

I'm confused, because I can't picture a "front" bed and "rear" bed. I can only picture port and starboard beds running parallel in a fore 'n aft orientation. Can you post a photo?

[RMeigel]

I'm confused, too. My CD 27 has one continuous molded fiberglass piece that the engine is bolted into, with the drip bed in the middle.

[John D.]

Robin & Bill - I don't have photo capability, but I'll try to describe . . .


The engine is mounted on one continuous piece of fiberglass bonded to the interior of the hull, but it is not a level plane. The "topography" includes the drip pan under the engine, which is more or less rectangular. At each corner of the drip pan, front/rear/port/starboard, there is a built-up bed, each of which, according to the manual, apparently has a piece of steel hidden inside it. It sounds as if some of you have two continuous fore-aft ridge on each side, rather than the four discontinuous ones that I have.

The installer is proposing to attach the front AND rear engine mounts to the forward bed, leaving the aft bed unused.

The image that comes to mind is the Disney ballerina hippo with the tiny feet. A caricature of instability.

P'sP - your expressed concerns about loading the prop shaft and torquing the beds were exactly what I was afraid of, and I appreciate your thoughts. BETA says it is no problem, but I'm not giving up that easily.

[Bill Goldsmith]

John,

Your instincts are correct, the installation should be on "all fours" and the engine should be solidly supported right at the location of each engine mount.

What is the installer's reasoning for avoiding the rear bed area?

Sounds like the existing raised mount areas in the bed don't match up with the engine mounts on the new engine. Not unlikely, since the original bed was probably designed to accommodate the original engine. The other extreme (and probably the superior way to deal with this) is to completely remove the old bed and start from scratch. This would mean glassing in two stout hardwood rails sized just right for the new engine. The cost in materials is minimal, however the labor is potentially significant.

Maybe a second opinion can be obtained from an experienced sailboat engine repower mechanic, to find a way to keep the existing bed, but support the engine properly.

[Kurt]

John,
The YSM-8 engine mounts are a bit unusual compared to conventional engine mount scenarios. Most engine installations have all four engine mounts sitting on two parallel stingers (port & starboard) in the same plane. The transmission is then hung off the bellhousing. The YSM-8 front mounts are fairly conventional. But the REAR mounts are mounted on the aft end of the transmission, much further aft then conventional thinking would suggest. And because of the upturn of the bilge aft of the engine, the aft mounts are mounted in a different plane. A picture in this case is worth 1000 words. Unfortunately I don't have a photo of a CD27/YSM installation handy for all you non-CD27 owners to take a look at.

When I installed a BZ482 in my CD27 3 years ago I did exactly what your mechanic is doing. I built up the existing front stringers (which are about 14'-15" long as I recall) using 2" white oak. All 4 of the Beta mounts sat down very nicely on the built up stringers. The oak does overhang the front of my factory stringers at the forward end but only by about 1". I used a belt sander to shape the aft end of the white oak pieces in order to mate the oak to the Cape Dory factory molded pan. Then glued/laminated the oak in place with epoxy resin and fiberglass cloth. Write to me off the board if I can offer more advice or answer questions. I can send you a photo or two of my installation if you'd like.
Kurt

[Duncan Maio]

I don't have photos or a dimensioned drawing, but the photo on the cover of my YSB-8 parts manual shows the mounts pretty clearly, and there is also a drawing in the operator's manual.

As Kurt indicated, the aft mounts are on a flange at the back of the transmission. the flange actually extends aft of the transmission, so the mounts are roughly in line with the prop shaft mounting flange. The forward mounts are under the starter and behind the alternator, or roughly 6-8" aft of the most forward parts of the engine.

The Beta 482 mounts are about 12" apart, and the overall (engine and tranny) length is around 25". Seems like most of the weight would be between the mounts. Unless the mechanic is proposing to alter where the mounts attach to the engine, I don't see a problem. The rear mounts are only 7" forward of the back of the transmission.

John:

I'd love to see some photos and hear about any needed modifications, and to know how performance improves - I am thinking about the same upgrade at some point in the future.

[John D.]

Thanks for all of the responses.

Duncan:

The mechanic had reversed the rear brackets, so instead of extending aft of the flywheel, they were forward of it, and the mounting base was reduced from 12" to about 6-7". I've received some good suggestions about how to extend the bed, so as to get a full 12". Right now, it looks like Kurt's oak stringers are going to be it.

Again, thanks to all.

[Duncan Maio]

John:

I'm with you, then. Moving the mounts closer doesn't seem like a good idea, when it' not such a big deal to modify the bed. My CD27 has continuous fore-aft beds, so I won't face the same problem if we ever tackle this same refit. In your situation, I would do the same - extend the existing beds and glass the extensions into the old. White oak and epoxy sounds like the plan. If you can't find the right thickness, you can always glue up (with epoxy) exactly what you need.

You might want to discuss with your mechanic how he intends to attach the mounts to the new beds, so you can make sure that the new beds will accomodate the least labor-intensive ($$) option. And remember, the engine bed is where the forward thrust from the prop is transferred to the boat, so the bed extensions need good fore-aft stability, too.

I'd love to see pics when you are done.

[Domenic]

I have decided to go with the BZ602. On my 1981 CP27 the Stringers are not continuous. It is four short stringers all molded with a drip pan. So, I will need to make new Stringers for the engine mounts. Here is my question? is the existing Stringers hollow? Thanks, Domenic

[Kurt]

Domenic,
Domenic,
If you currently have the YSM-8 installed, then you have the same pan I have in my 27. The front stringers are hollow. The aft mounts are really not stringers, but rather engine mount pads molded into the pan to accept the rear YSM mounts hanging off the back end of the transmission as has already been mentioned in this thread.
But why the BZ601? Are you planning to go into the towing business after the install is complete? Seriously, the BZ482 will push a 27 along at 6knots while turning 2500 rpm...what more would you want? The BZ601 is bigger and will be a bit more difficult to shoe horn into the 27. Also, because there's more rotating mass (bigger pistons, con rods etc.) the potential for more vibration exists. Just my 2 cents...please don't take offense that I'm questioning your decision.
Kurt

[John D.]

I went with 1"x4" oak boards, 2 per side, because it allowed more precise shaping to the liner/hull, and gave me new beds that in exactly the same plane as a broom handle stuck in the prop tube.

Here are my steps.

1. Run halyard from masthead, through a turning block temporarily tied to boom, to directly above companionway; attach double sister block; attach double sister block with cam cleat to engine mounting lugs; and remove engine that mechanic had mounted improperly (all by myself! why did it take him 2 months and a crane for that step?)

2. Belt sand front stringers, which are not perfectly flat, to make them flat in teh front portion. I do not say level, because they are sloped.

3. Measure rough size, and cut 4 pieces of 1" x4" oak, (for me, 21" long). Label each one, e.g., "Port, lower, this side up", etc.

4. Cut 8 pieces of 0.25" x 0.25" x 12". lay side by side on top of stringer, pushing each one aft until it contacts liner/hull. It will look like a Pan flute. (anyone remember those ads for Zamfir - the Master of the Pan Flute?). Put a piece of masking tape across the Pan flute, lift it off, and trace that profile onto the bottom of a 1" x 4".

5. Put the 1"x4" on the stringer, and repeat #4, with the Pan flute on top of the 1" x 4" this time. Trace again.

6. Take on deck and go to work with the jig saw along the top profile line, and then join the two profile lines using a belt sander.

7. Repeat for the other boards.

8. Now for the epoxy. Using WEST System, each joint took 4 pumps each of resin and 205 hardener, with a LOT of colloidal silica thickener, almost peanut butter. I put a 1" thick bead of that down the middle of the original stringer, and some on the bottom of the board to wet it out, then pressed together. At the aft end, where the curves are, it took a lot of epoxy. It has to be thick, or it will ooze out before it sets.

9. Repeat for top board, and then tape and wedge in place (there is nothing to clamp to.

10. Repeat for other side.

11. Paint straight eopxy onto all sides of oak.

12. Use 5/8" lag screws (2" long in front, and 1.5" in back) to attach motor mounts to new oak stringers.

Thanks to everyone for the shared experience!

[Kurt]

Excellent work John! I would also suggest, if possible at this point, that you wrap some 6oz. fiberglass cloth/epoxy resin over the oak and drape it down onto the original fiberglass stringers for an even stronger bond between the oak and fiberglass.
Kurt

[Domenic]

Thanks Kurt. I would never take offense. Thanks for your help. Now, Is that drip pan removable? Do I remove the Drip pan and do what John D did? Or do whad John D did on top of the drip pan. Do I put the new stringers on top of the molded drip pan. Thank so much Kurt and John D for the help, Domenic