#1 2020-09-22 21:02:39

Registered: 2020-07-27
Posts: 2

Changing engine on V26

I am a new owner of a beautiful V26 named Vagabond, previously owned by Alan.

At the end of this first season in the mediterranean sea,  I realize that Vagabond is the perfect sailboat for me.  I am an happy sailor proud to sail on a beautiful boat.

However the med sea may be a capricious sea and the wind can be fairly changeable.
In this situation, a  powerful engine is a guarantee of security.The small yanmar 1GM10 engine that powers Vagabond quickly shows its threshold in that case.
So in the next few months, I intend to improve the power by  changing  the 1GM10 by another one
more powerful.  Gaining more power and torque is the only reason for changing as the current engine is in good condition .

I will appreciate to get some advice about what kind of power and engine will fit the best. I am thinking about a yanmar 2YM15 (14hp) or 2YM20 (21hp) , a Volvo D1-13 (12hp) or D1-20 (18hp) or any other engine like beta or nanni.
In the other hand, can anybody tells me what will be the best size of propeller for the intended engine  (the current one is a 12’’ 3 bladed prop).

I am looking forward of reading any reply that will help me in my choice.

Best regards from an happy sailor on his beautiful sailboat.


#2 2020-09-23 15:58:35

Registered: 2017-05-26
Posts: 23

Re: Changing engine on V26

Hi Jean,
You are right in that the GM10 is, in truth, only 8 or 9 HP so has a struggle against wind and tide.
A popular option you may want to consider is the Betamarine 16HP.
I have this in my Frances 26 and also fitted one in a Cornish Yawl (to replace the Yanmar GM10).
14HP would be fine and 16HP leaves power in reserve. (in fact the power pushes the stern down when applied).

Another association member, Andrew Gleadle went through the process of replacing his GM10 with a BETA 16 last year in his Frances 26 so I'm sure would be able to share with you some of the benefits (and challenges) of the fitting process.  It may well be worth dropping him an email. 

I hope this helps.
Kind regards,



#3 2020-09-23 20:57:25

Registered: 2014-09-23
Posts: 34

Re: Changing engine on V26

Hi Jean

As mentioned by Kevin, I have a Frances 26 and replaced the 1GM10 with a Beta 16 at the end of last year.

I agree with you that the 1GM10 lacks power in strong head winds and tides and I have often found myself almost at a near standstill in certain circumstances.

For a replacement I looked at Yanmar and Beta as possible options and decided on Beta as they are lower price and good quality, support in the UK is very good and a number of Beta engines have been successfully fitted in Frances 26's already.

I have a 13 x 9 three bladed prop on and it drives the boat very well with a comfortable cruising speed of 5kts at around 2100 revs. This leaves plenty of extra power when needed. Another benefit of the new engine is the ability to stop a lot quicker. The prop is the same one I used with the 1GM10.

After going through the process of the replacement and appreciating the benefits this year I can thoroughly recommend changing to a more powerful engine.

Please feel free to drop me an email if you would like some photos or additional information



#4 2020-09-24 10:50:46

Registered: 2004-03-23
Posts: 101

Re: Changing engine on V26

You are right to consider the transmission of any power increase that you install, and for that you need to firstly look at the propeller size and the propeller rpm.

Realistically, the max diameter prop you can put in is 13” diameter.   Your current prop is probably a 12” x 9”.    If you put, say, too big an engine in, then the only way to transmit the power is by a high shaft speed (ie. Low gearbox ratio) or with a high pitch propeller.    However, the time you really need plenty of power in short seas, what you want is big surface area, big diameter and smaller pitch – ie pitch is  really more useful for faster speeds.   So the F26/V26 has a maximum useful engine size due to transmission, even before considering max hull speed etc.

2YM15 – weight 103Kg; engine max rpm 3,600, gearbox ratio 2.21/3.06:1
3YM20 – weight 110Kg; rpms etc as above
D1-13 – weight 111Kg, engine rpm 3200, gearbox 2.14/1.95:1
D1 – 20   weight 132 kg; rpm’s as above
Beta 14 – weight 90Kg; engine max rpm 3,600; gearbox ratio 2:1
Beta 16 – weight 95 Kg; rpm’s  as above

Nanni similar to Beta as far as I know.

You could put on different gearboxes to some of these, so you might be able to change some of the shaft rpm’s.

There is at least 1 V26 with a 3 cylinder Beta 20hp.   Quite a few have changed to 14hp Beta (or Nanni), and a couple of Beta 16.

If you look at the above engines and gearbox combinations, (and assuming you choose the faster speed for forward), maximum prop speeds are:
Yanmar – 1629 rpm
Volvo – 1641 rpm
Beta/Nanni – 1800 rpm
Because of this there is a bit more scope for propeller size options with the Betas.   You will also notice that in reverse there is full thrust with the Beta engines, whereas, particularly the Yanmar, prop speeds are more reduced.

For the Beta 14 you can use your existing prop to good effect.    The Beta 16 you can change to a 13 x 8.   In fact, you could use a 13 x 8 with the Beta 14, though you will not achieve max rpm.  The 20hp will take a 13 x 9.    It would be interesting to hear what the max rpm Andrew gets with a Beta 16 13x9 combination.

There is an argument that you should not overpower too much as a marine diesel likes to be worked at perhaps 60% to 70% of its rated power.  If you cruise with say 8hp, you would only be using 40% of available power with a 20hp,  or about 60% of a 14hp.    For this reason alone, some would consider 20hp as rather too much.

Regarding propellers – the bigger the diameter/surface area, the greater the drag whilst sailing.   So it could be that you upgrade to a 13 x 8, but find that it affects your sailing performance, particularly lighter airs.   As an option you could look at a feathering prop to solve this, though this also has pros and cons.

Weight is another consideration – all the options are heavier than the 1GM10, but still quite a big variation.    Might also be worth you looking at fuel usage for a given power level.

Betas/ Nannis fit well on the existing engine bed.   Suspect the Yanmars and Volvos don’t without modification, though I have not looked at the physical fits for them all.   

Worth looking at access to key service items, particularly bearing in mind your boat design.

Spares:   I have always been told that because the Beta and Nanni are based on Kubota engines, spares are easier to come by, and cheaper than other makes.   

I changed to a Beta 14 which I have been very pleased with.   The Beta 16 was not an option at the time, and if it was then I would have given it serious consideration.  I think 20hp is too much, and I have my doubts as to whether you can swing a big enough prop for the Yanmar/Volvo 20 to use the additional power.


#5 2020-09-26 22:15:56

Registered: 2014-09-23
Posts: 34

Re: Changing engine on V26


At full throttle with the Beta 16 and the 13 x 9 prop I'm at 3000rpm with just over 6 kts of speed. This was fed back to Beta and they appeared happy with it.

I discussed the Beta 14 vs the Beta 16 with the engineer who was helping me fit the engine. The 16 is 14mm longer, weights 5kg more and was very slightly more expensive but does offer the extra power.

The price and size were acceptable and as 95% of my sailing is singlehanded, I'm not worried about the weight (a crew member = 70Kg+). The extra power is useful as I found out last weekend leaving Poole.

With the Beta Cross Over injection bend I kept the waterlock on the starboard side as per the 1GM10. This simplified the installation and enabled me to maintain good access to the rear of the engine via the pilot berth access hatch.

I hope this information is useful.



#6 2020-09-28 11:02:00

Registered: 2020-07-27
Posts: 2

Re: Changing engine on V26

Hi Andrew, Jonathan and Kevin.

First of all, I personaly want to thank all of you for your helpful answers and useful contributions.

That convinces me to replace the 1GM10 by an engine powered with 14hp (minimum) or 16-18 hp (maximum) and a prop of 13"x 8" ou 9".

Yanmar 2YM15, beta 16 (or nanni 2.14) and lombardini LDW702M W (18hp) are in the short list of choices. I am waiting for the quotes and the study for the installation.

To Andy. I will appreciate to receive some pictures as you ve suggested it. I will drop an email.

Thank you so much.



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