Bukh 20 -> Beta 20 bed issues?

[dgadee]

Awaiting news on whether the Seawolf is economically repairable and I have an alternative in mind should it not be. A lot of the ones I see are powered by old Bukh 20 raw water cooled engines (223Kg) and I would re-engine with a Beta 20 (100kg). I previously replaced a Vetus (160kg) with a Beta and was able to make up fittings to use the old engine bed. Anyone done this with Bukh to Beta? Were there problems in getting the gearbox lined up with the existing shaft?

 

[LittleSister]

Have you spoken to Beta? I would be surprised if they hadn't made feet for that same conversion before.

The Beta is more compact, so it shouldn't be a big problem. If I recall correctly,
- most Bukh 20s will have the BW6 gearbox, who's output shaft is rather lower than the input shaft/engine crankshaft, so the new engine will sit lower;
- those engines rotate in the opposite direction, so you'll need a new propellor;
- they've different exhaust and inlet hose sizes, might require different skin fittings.

You can probably find a dimensioned drawing of the Bukh 20 somewhere online* (check whether the same gearbox you have). There's dimensioned drawings of the Beta 20 (with various gearboxes?) on the Beta website.


* p.s. Bukh 20 dimensioned drawing here - Size and Weight of Bukh DV20 ? - Cruisers & Sailing Forums
Beta 20 dimensioned drawing here - B20 HE DataSheet REV 05 1121

 

[dgadee]

Thanks.

 

[vyv_cox]

I replaced a Bukh 20 with a Yanmar 3GM30F. 2 X bearers 1 inch high aligned it well, exhaust was a different size, water supply went from 1/2 to 3/4 inch. I kept the same prop for a season, went reasonably well on it.

 

[PetiteFleur]

Beta can make customised feet to suit your existing bearers - for me with a Beta 25hp replacing a BMC 1500.

 

[dgadee]

Looks like just a few mm difference - 20mm wider on Bukh and 8mm difference between bottom of bearer on engine and centre of gearbox output. Probably don't need plates made up if the boat bearers are of sufficient breadth.

 

[DownWest]

Replacing a Yanmar 2GM20 with a Beta 16 I found that the new rubber mountings were much shorter than the Yanmar ones, so the gap between the mountings and the feet was too long . Rather than delay things by getting back to them about the installation (this being in France..), as they knew which boat was involved, I just fitted 30x60 galvanized tube spacers under the rubber mounts. This reduced the gap to within the mounting outfits recommended specs. Lining up the shaft was not a prob, liked the coupling supplied by Beta, but had to redrill the shaft flange as the PCD was different.
The cross over exaust supplied was larger diameter than the old, so I built up the inlet to the Vetus water trap with glass tape and resin. The raw water inlet just needed fresh tube to the bigger size. The only unexpected hiccup, was the exhaust cross over needed a box in the rear of the engine cover to accomodate the bulge (aft double cabin)

Oh, on first start up, it fired as soon as I turned the key. Bit startled, as the old donk required a bit of churning. Much smoother and quieter too.

 

[Tranona]

Depending on the boat it might be worth considering a 25 as many boats at the time were underpowered with the 20 because the next size up was a 30. The key criterion is displacement. Once you get to around 4 tonnes design displacement then you won't be able to get to hull speed with a 20 on a typical sailing cruiser like a Sadler 32, Westerly Fulmar etc. and the small additional cost for the bigger engine is well worthwhile.

 

[dgadee]

Depending on the boat it might be worth considering a 25 as many boats at the time were underpowered with the 20 because the next size up was a 30. The key criterion is displacement. Once you get to around 4 tonnes design displacement then you won't be able to get to hull speed with a 20 on a typical sailing cruiser like a Sadler 32, Westerly Fulmar etc. and the small additional cost for the bigger engine is well worthwhile.

Yes, I understand but my hope is that I can move the Beta 20 from the Seawolf and not have to buy a new engine.

For interest, Beta gave me current pricing (including discounts):

• Beta 20: £5664.00 delivered including VAT.
• Beta 25: £6068.00 delivered including VAT.

So if I had to buy, the 25hp would be the better choice.

 

[fredrussell]

Just out of interest, are both the Beta engines 3 cylinder?

 

[dgadee]

Just out of interest, are both the Beta engines 3 cylinder?

Yes.

 

[Rhylsailer99]

How about replacing it with a Bukh dv24 it will slip straight in .

 

[dgadee]

How about replacing it with a Bukh dv24 it will slip straight in .

Never.

 

[Rhylsailer99]

Never.

I can understand why as they do weigh a ton.

 

[doug748]

Awaiting news on whether the Seawolf is economically repairable and I have an alternative in mind should it not be. A lot of the ones I see are powered by old Bukh 20 raw water cooled engines (223Kg) and I would re-engine with a Beta 20 (100kg). I previously replaced a Vetus (160kg) with a Beta and was able to make up fittings to use the old engine bed. Anyone done this with Bukh to Beta? Were there problems in getting the gearbox lined up with the existing shaft?

5mm stainless plates bolted/screwed down to the original bearers make a flexible option, as long as you don't need to lose height on the installation. Too low and it's an easy fix.
With new plates, if you can't contrive to get a nut and bolt through the engine foot and plate you can always tap them.

Anything over 20hp on your boat and you will never use the power available but may convince yourself you need a new prop into the bargain.

.

 

[Tranona]

Anything over 20hp on your boat and you will never use the power available but may convince yourself you need a new prop into the bargain.

.

Can't see any indication of what the boat in question might be, so how does one know what power is required? Se post#8. Power required is almost a direction function of displacement. A Seawolf 30 is OK at 3600kgs with 20hp, but if the alternative the OP has in mind is heavier then a 25hp may be more appropriate. However with the new information that the intention is to use the existing 20hp in a different boat it may well be that one has to accept a less than desirable level of performance.

 

[GHB]

I replaced bukh 20 with beta 35 & used a length of 2" x 2" hardwood to get the new feet bolt positions & lift the feet as well. Not sure if the footprint & section of the feet is same for a 25 though. Cheap(fairly) and it worked though.
Got a 3d cad somewhere if it's any use.

 

[doug748]

Can't see any indication of what the boat in question might be, so how does one know what power is required? Se post#8. Power required is almost a direction function of displacement. A Seawolf 30 is OK at 3600kgs with 20hp, but if the alternative the OP has in mind is heavier then a 25hp may be more appropriate. However with the new information that the intention is to use the existing 20hp in a different boat it may well be that one has to accept a less than desirable level of performance.

Yet you know he would be better off with 25hp? Odd that.

 

[dgadee]

Fulmar, 4500kg. My Dehler is 5300kg and has a Yanmar 30 which is very, very rarely run above 2500 revs.

I do think 25hp is better, but not if I have a 2 year old Beta 20hp to hand. We will know soon.

Image shows bow damage on Seawolf. A goodly bit of delamination on s/b side. I think it is on its way to the scrap yard. Hopefully not.

 

[Tranona]

Yet you know he would be better off with 25hp? Odd that.

Just read what I said in post#8. The advice was conditional - if the boat exceeds 4 tonnes then it is better to go for the 25.

It is your comment that seems "odd" as you are categoric that he only needs 20hp when you have no idea what boat he has in mind.