Swapping Perkins 4108 to Beta 50

[peter57]

Originally Posted by sailor_ed

I am curious as to where the "rule of thumb" value of 5hp/liter comes from. Is this well known to yachties ?

Your figures on your Gulfstar in your previous post are around 5hp/L and you could probably do a little better without overloading with that new Beta Nanni.

In 1994 I nearly spent $15,000 to do the same Nanni replacement of my 1981 year make 4108 luckily found the right people and spent $150 re-pitching the prop (3 inches) and she still runs today with the new owner.

Shape, wetted surface area and weight of your boat at my guess would be 15 shp
which at cruising speed would be around 3L/h. There are smart people in this business who would know, not me.

My boat 42.6' is a bit more slipperier than yours at a guess but heavier (steel) and powered by a 39 hp Yanmar 1850 rpm at max torque 6.5 knots, 2.2 L/h smooth water. This might be overloading slightly but still get to full rpm of the motor specs (another rule of thumb), overloading will told by the exhaust elbow matter apparently on a Yanmar.

[DougR]

Originally Posted by kmacdonald

That's impossible. A very efficient turbo diesel burns about 1 gallon per hour for every 20 HP. A small naturally aspirated mechanical diesel burns about 1 gallon per hour for every 18 HP. The Beta chart shows max HP at 2200 rpm. The fuel burn at 2200 rpm doesn't give the engine load. Could be no load at all for all we know. The chart says "fuel consumption based on theoretical prop loading" not max output.

No, the Beta graph shows max. HP at 2800 rpm, not 2200. If you overlay a theoretical prop load curve with an exponent of 3 onto the power graph, (which is what Beta says the consumption is based on), then you see that the prop load will show a consumed power of perhaps somewhere between 25 and 30 h.p. Thus the numbers quoted by Beta begin to approach the realm of possibility.

Of course the consumed power isn't 43 HP....it's much less. Remember the power curve shown in the graph is the full load power curve of the engine, not the prop load curve.

DougR

[Wainui]

Originally Posted by DougR

Wainui,
It might not be so much a question of the money, but whether the Beta transmission can be made to work well with the v-drive....

- With a Walters remote v-drive, the final drive ratio of the system will be the product of the regular transmission ratio times the v-drive ratio. Frequently the BW gearbox will have a 1:1 ratio and the rest of the reduction will be taken in the Walters v-drive. If this is your arrangement, then you need to use a 1:1 Beta transmission to maintain the same final ratio. Of course it may be that you don't want to maintain the same ratio because the Beta operates at a different max. RPM than the 4-108. This all needs to be examined.

- The BW gear is probably a co- axial output gearbox, meaning the output shaft is on the same line as the crankshaft, but the Beta gearbox might be a drop center gear, where the output shaft is lower than the crankshaft. This means that the u-joint angles between the engine transmission and the Walters will be different between the Beta transmission and the BW. This may or may not be acceptable and should be discussed with a knowledgeable installer or Walters Machine Co.

- The 4-108 engine turns counterclockwise when viewed from the flywheel and the output of the BW gear is probably the same. It may be that the Beta gearbox will run continuously in either direction, but maybe not. If the rotation isn't the same as what you have now, you might need to be looking at a different rotation propeller.

DougR

Hi Doug
I’m going with the Beta and my BW Velvet Drive.
They will include a transmission cooler mounted on the engine.
The Beta turns counter clockwise same as the Perkins.
Will let the forum know the details on any pitch changes.
My only concern is how the Walters Vdrive handles the extra hp.
Many thanks for all comments and advice.

[Wainui]

After looking at the Walters manual I found the following formula for the R10 Vdrive.
HP/100rpm is 1.5
So if my math is correct a 50 hp at 2800rpm is 1.78
Can the Vdrive handle the extra torque?

[kmacdonald]

Originally Posted by Wainui

After looking at the Walters manual I found the following formula for the R10 Vdrive.
HP/100rpm is 1.5
So if my math is correct a 50 hp at 2800rpm is 1.78
Can the Vdrive handle the extra torque?

Your v-drive is good for up to 42HP. (2800/100 X 1.5)
Check to see if that rating is a pleasure rating or commercial rating. Pleasure use ratings are quite a bit more than commercial use ratings.

[kmacdonald]

Originally Posted by kmacdonald

Your v-drive is good for up to 42HP. (2800/100 X 1.5)
Check to see if that rating is a pleasure rating or commercial rating. Pleasure use ratings are quite a bit more than commercial use ratings.

I should have made it clear that the above is only correct if there is no reduction gear before the v-drive. If the is a 2:1 reduction gear before the v-drive the RPM's would be 1400 instead of 2800 RPM's. In that case it will only handle 21HP. (1400/100 X 1.5)

Gears have a maximum torque value they can handle. A reduction gear is a torque multiplier so the gear ration is important to consider. An engine producing 50 ft-lbs of torque coupled to a 2:1 gear will apply 100 ft-lbs of torque to the prop or v-drive.

[DougR]

Typical installations of Walters remote v-drives consist of a 1:1 Borg Warner transmission and a Walters remote v- drive, where all of the system reduction is taken in the v-drive. So you need to determine if you have a 1:1 BW and you also need to determine the reduction ratio of the V- drive. Typically transmissions have different power capacity depending on the reduction ratio.....the more reduction, the less capacity. Also be sure you are looking at the RV-10 capacity tables for diesel engines. Transmissions frequently have reduced capacity for Diesel engines as opposed to gasoline engines.

Last thing to consider is that your Beta is rated at 50hp @2800 RPM, but that power is being fed thru the Borg Warner gear before it gets to the Walters. You should consider that the BW gear will produce losses of about 4%, so the Walters will really see 48hp @2800 on its input shaft.

DougR

[Wainui]

I contacted Walters to find out if either a Beta 50 or a Yanmar 54 would be ok on a 1-1 BW to a 2-1 Vdrive.
“54 HP @ 3,000 rpm should be fine”
Looks like it will not be a problem!

[leftbrainstuff]

Originally Posted by stormalong

Let's see. Smoother running, less pollution, less oily mess under the engine. Parts available worldwide from Kubota. No unexpected rebuild costs that could drive the cost of the rebuild close to the cost of a new engine.

The 4-108 went out of production in 1992. There are no "new" 4-108s.

Why would't you want to replace it?

A mechanical diesel is the ultimate in reliability. They are easily and cheaply rebuildable.

I could care less about marketing bs about emissions. Our perkins 4-236 is very smooth, has no leaks and efficient.

I spent 10 years as a professional mechanic in global motorsport so have spent plenty of time with high tech engines. On a cruising sailboat I don't want anything other than a fully mechanical diesel.

[kmacdonald]

Originally Posted by leftbrainstuff

A mechanical diesel is the ultimate in reliability. They are easily and cheaply rebuildable.

I could care less about marketing bs about emissions. Our perkins 4-236 is very smooth, has no leaks and efficient.

I spent 10 years as a professional mechanic in global motorsport so have spent plenty of time with high tech engines. On a cruising sailboat I don't want anything other than a fully mechanical diesel.

I agree but don't know that mechanical diesels will be made much longer. Volvo had to recall and replace a lot of engines that didn't meet emission standards they were required to. I bet more will follow.

[jewt]

My Beta 43 hp. swing a 17" 3 blade at 1800 rpm and pushing my 22,000 # Morgan 41 K/CB @ 5.7 kts and would burn 0.7 to 0.8 gal/hr, at 2200rpm she would make 6.8 but would burn 1.0 gph.(2400 is all she would turn maxed out but would not overheat) The hull was full keel attacked rudder and a 3 blade 17X 12 prop. No computer to be killed by a lighting strike and no damn turbo.

Three trip to and from the Bahamas from North Carolina without a hitch except for the Italian tranny.


Go for the Beta and all you have to worry about is dust on the engine, no more oil leaks.

Jewt

S/V Bifrost

[Lepke]

The issue with 4108 rear main leaks is the proper installation of the old style rope seal. Most of today's mechanics do a poor install. If the crank is scored, the score area can be ground and hard chromed to original size with a surface that will last forever. It's a common process on bigger engines with journal damage. Hard chrome is not the same as shiny chrome. Although even with scoring, a rope seal should control the oil leak.
My current 4108 generator is a 1972. And ditto on mechanical engines.

[stormalong]

Originally Posted by Lepke

The issue with 4108 rear main leaks is the proper installation of the old style rope seal. Most of today's mechanics do a poor install. If the crank is scored, the score area can be ground and hard chromed to original size with a surface that will last forever. It's a common process on bigger engines with journal damage. Hard chrome is not the same as shiny chrome. Although even with scoring, a rope seal should control the oil leak.
My current 4108 generator is a 1972. And ditto on mechanical engines.

OK, The crankshaft can be removed, machined and hard chromed back to original spec. In other words a complete engine rebuild + additional work. I would like get a cost comparison between that complete rebuild vs a new engine.

When I was trying to decide between rebuilding my 4-108 and replacing it with a new, more modern engine I came to the conclusion that the rebuild would only be practical if there were no complications. A bad crankshaft would have put the rebuild over the cost of a new engine - I would not know about cost overruns until I would be fully committed to the rebuild.

Then I thought about my thirteen years of of owning and maintaining the 4-108 and what I would like to have in a replacement engine. The engine was under powered for my boat. The alternator was inadequate and going larger was an issue with side loading the engine main bearing. Because mine was a "V" drive some service points were difficult to access.

I was wintering in London that year and attended the London boat show. I made contacts with two or three engine makers. Beta Marine was a two hour train ride from London. After a few phone conversation with them we visited the factory. We discussed the customizations I wanted and was quoted an excellent price. Dealing factory direct was a big advantage.

I did the engine swap myself except for hiring a crane to haul out the old engine and lift in the new. That was in 2003 and 4000 engine hours later I am still very happy with my decision.

[Wainui]

Stormalong which Size Beta did you go for?

[stormalong]

Originally Posted by Wainui

Stormalong which Size Beta did you go for?

I installed the 50 (BV2203).

The 50 and the 43 are the basically the same engine, just a different bore.