Swapping Perkins 4108 to Beta 50

[oldcal46skipper]

If anyone within 1,000 miles of Pensacola, FL removes their 4.108. Please PM me and I will probably buy it and pay shipping.

Tom

[Wainui]

I’m pulling mine next week in La Cruz PV Mexico

[Wainui]

I have just finished swapping my 4108 to a BM 50 here in La Cruz PV Mexico.
All went well. Kept the BW Velvet Drive which mated up fine.
New engine is smoother and quieter with more power than the Perkins.
Happy camper.
Glad I did it.
Thanks to the advice.
M

[jewt]

I think you will be very happy with the match.

Smooth sailing,

[jewt]

I think you will be very happy with the match.

Smooth Sailin'

jewt
S/v Bifrost

[Wainui]

Had to re pitch the max prop.
Vdrive was a 1.67-1
Pitch is 16 degrees on a 17” 3 blade.
Max rpm in gear is 2500 rpm doing 8 knts which is at least 1 knts faster than the Perkins.
Cruising rpm is 2200 rpm doing 6.8 knts
Haven’t worked out fuel consumption yet.
Engine sound great less noise and vibration.
Happy that I have done this but it’s not cheap $20k
Thanks for all the advice.
M

[Scrubcutter]

Interesting discussion. Has anyone had any experience swapping a 4108 over to a B50 on a Cape Dory 36?

[skipperpete]

I did the 4-108 swap to Beta 50 in a Westsail 33 and it was a bit tricky, the Westsail has bugger all room down in that deep Vee, even for the Perkins.... but it ended well. How deep and narrow is the cape dory machinery space?

[Scrubcutter]

Originally Posted by skipperpete

I did the 4-108 swap to Beta 50 in a Westsail 33 and it was a bit tricky, the Westsail has bugger all room down in that deep Vee, even for the Perkins.... but it ended well. How deep and narrow is the cape dory machinery space?

I did some rough measurements yesterday and my engine bay is roughly 80W x 70D (to base of current front bearer) x 110L (front of compartment to shaft coupling), measurements in cm. Looking at the data sheet for the Beta 50, it appears a bit longer than the 4108 and Hurth box, but width and depth are comparable. Unless I drop to a B38 then the next model down (B43) is roughly the same as the 50. Did you find you had to modify the mounts extensively? I assume yours would have been the same as mine are for your 4108.

[skipperpete]

Originally Posted by Scrubcutter

I did some rough measurements yesterday and my engine bay is roughly 80W x 70D (to base of current front bearer) x 110L (front of compartment to shaft coupling), measurements in cm. Looking at the data sheet for the Beta 50, it appears a bit longer than the 4108 and Hurth box, but width and depth are comparable. Unless I drop to a B38 then the next model down (B43) is roughly the same as the 50. Did you find you had to modify the mounts extensively? I assume yours would have been the same as mine are for your 4108.

Beta supplied the engine with the brackets and mounts already modified to match the Perkins footprint from the owners measurements, so that made it easier but the gearbox end was difficult and the high output alternator came up against other equipment and the bulkhead.

[Scrubcutter]

Thanks, that's good to know. Beta has a catalogue of boats which they already have info for, unfortunately CD36 isn't one of them and as with any older boat, a lot of things get retrofitted in the engine room over time. I have asked the local dealer in New Zealand for a quote and will do some more measurements on the weekend. Thanks for your info

[skipperpete]

The surest way to do a painless engine change is to carefully measure the Perkins brackets and footprint then supply those dimensions to Beta. It’s possible that the existing Perkins brackets might have been modified previously to fit the CD36.

[kmacdonald]

Originally Posted by Scrubcutter

I did some rough measurements yesterday and my engine bay is roughly 80W x 70D (to base of current front bearer) x 110L (front of compartment to shaft coupling), measurements in cm. Looking at the data sheet for the Beta 50, it appears a bit longer than the 4108 and Hurth box, but width and depth are comparable. Unless I drop to a B38 then the next model down (B43) is roughly the same as the 50. Did you find you had to modify the mounts extensively? I assume yours would have been the same as mine are for your 4108.

The Beta 30 or 38 would be plenty of power. My Bristol 35.5 has a Kubota D1105 thats 25 HP @ 3000 rpm. Same as the Beta 30 except they run it at 3600 rpm to get the 30 HP. My boat does hull speed with the 25 HP Kubota. I guess if you cruise dock to dock you might want the Beta 38. 50 HP is way overkill.

[Scrubcutter]

Originally Posted by kmacdonald

The Beta 30 or 38 would be plenty of power. My Bristol 35.5 has a Kubota D1105 thats 25 HP @ 3000 rpm. Same as the Beta 30 except they run it at 3600 rpm to get the 30 HP. My boat does hull speed with the 25 HP Kubota. I guess if you cruise dock to dock you might want the Beta 38. 50 HP is way overkill.

Yeah, but a 4108 develops 47hp @ 3600 rpm (mine doesn't because it blows blue smoke over 1000rpm, one of the many reasons I am retiring it!) and the Beta 50 is the closest in weight power and dimensions to the 4108. My CD36 is currently around 9500kg on the travel lift so quite a bit heavier than a Bristol 35.5. I regularly have been underpowered beating upwind against a current when it blows up, something I would like to have a bit of reserve power for as these conditions are not unusual in my part of the world. I will definitely discuss options with the Beta dealer to get the best size for a replacement.

[Cpt.Steve]

Scrub cutter, are you still pondering this repower? If so, I would implore you to reconsider the sizing, though I am sure beta would have told you the same.

An old 4108 would actually have used a different formula for determining HP. Compared to the Beta numbers it’s actually producing closer to 40hp, or even 37hp is often touted. We have a Beta 35 in our Tartan 37 at 16,000lb mostly dry and happy cruise at 6.5 pushing 7.2 when we really put it to her. I would think the Beta 38 would be a much better fit.


** For others who have gone from a 4108 to a modern 50hp. Did you have to go up in prop shaft size? What did your reps suggest? Our new boat was soec’d with a 1” shaft for a 4107/8 with 2:1 reduction (BW vd to a Walter V). Curious if anyone is running a 1” with 45-50+ hp. Thanks