Re-engine 28 foot boat - 14 hp enough?

[johnalison]

I re-engined our Stag 28 20 years ago (Jeez!) with a Beta 14. At the start of the season we can get hull speed, 6.5 knots, with relative ease inside the harbour. As the seaon progresses, if we don't scrub off, we gradually come down to around 5 knots or so. I can honestly say I've never needed nor particularly wanted any more horses. So yes, the Beta 14 is perfectly adequate for this size of boat.

We used to cruise in company with a Trapper 501 bilge keel which had a 10hp engine. They managed well enough but eventually changed to a 15 hp motor that was much livelier. I would think that a Seal was probably more easily driven and that 14 hp would be plenty. We found that with 18 hp in our Sadler 29 we were almost over-driven and had no problem with Channel and N Sea crossings.

 

[jwilson]

Once had a old long-keel sailing yacht about twice the displacement of your Seal 28 that had a 7 hp Volvo MD1 with Dynastart. At the time it seemed fine. These days I have 27 hp on a modern 35-footer.

 

[Refueler]

A 1 cylinder, 8hp engine was just about up to the job of powering a 24ft Snapdragon when new. The one in mine wasn't, and it died a year or two after I bought the boat. I was given a VP2003 which, even though it had 3 cylinders, and adding a dedicated starter battery, it was lighter than the old lump.

28hp in a Snappy was a joke, but I never regretted having that extra power if I needed to punch a tide, especially in a bit of chop. I can't help thinking that, while 14hp might do the job, you'd never regret spending a bit more and getting 20 - or even a bit more, if you've ever wished for a bit more umph from the Bukh.

Snap 23's were offered with a Vire 6 originally !!

 

[Refueler]

My 38ft 5ton has a 20HP 2GM Yanmar ...

 

[Poignard]

I seem to remember Eric & Susan sailing round the world in 'Wanderer III". A 30-foot yacht equipped with a new to them luxury, a 4hp Stuart-Turner petrol engine.

 

[KevinV]

I have no particular opinion on this particular fit, except that I'm very much of the "auxiliary engine" camp.

What I do wonder with those advocating larger engines than those that were deemed sufficient by their designers... how does that tally with diesels generally preferring to be run hard? I'm surprised we don't hear more about glazed bores and the likes from under stressed larger engines

 

[Refueler]

I have no particular opinion on this particular fit, except that I'm very much of the "auxiliary engine" camp.

What I do wonder with those advocating larger engines than those that were deemed sufficient by their designers... how does that tally with diesels generally preferring to be run hard? I'm surprised we don't hear more about glazed bores and the likes from under stressed larger engines

My Sunrider 25 MS .. 4ton .. has a 43HP Perkins 4-107 ..... and a great big lump of concrete under forecabin sole ... I can do 9kts with it .. but usually have it about 30% throttle and 4.5 to 5kts ...

The original Bristows showed it offered with a Mercedes 12HP ... one of the few I ever noted saying Mercedes !!

 

[Boathook]

One little known fact, and even less adhered to, is that fitting a bigger engine with more than 15% increase in horsepower would under RCR / RCD constitute a major change and require a recertification (“post construction assessment” or PCA).

>>>>>>>>>
In RCR 2017 there are four triggers that invoke PCA of a boat:

A. It has been imported and is not in conformity with RCR 2017. This requirement is listed at Regulation 24 (1) and 43 (1) of the RCR 2017. For example, this could be a private individual bringing a sports boat into the GB from USA.

B. A vessel previously not in scope of the RCR 2017 has a change in its intended purpose, for example a new boat designed to be a work boat becomes a new recreational vessel instead (Regulation 43 (2) (b)).

C. A private individual who has built their own boat for own use wishes to sell it within5 years of first use (Regulation 7 (1), Regulation 43 (3)).

D. If it has undergone a major craft conversion (MCC). This requirement is listed at Regulation 3 (F) in RCR 2017. A major craft conversion is defined in the interpretation as having happened if it:

a. changes the means of propulsion of the watercraft; “means of propulsion” means the method by which the watercraft is propelled

b. involves a major engine modification;

i. could potentially cause the engine to exceed the emissions limits set out in Part B ofSchedule 1;

ii. increases the rated power of the engine by more than 15%;

I suspect that the OP's boat is well before RCD so would it apply ?
Some boatbuillders years ago quite often gave a choice of engines. Mine could have had in the day, petrol dolphin of around 10hp, diesels 10 to 15hp or outboards 20 to 40hp. The default eventually became diesels of 15 hp.
Being a cat, the inboards were twin and the outboards single.

 

[neil_s]

My Seal 28 is from 1977 so RCD doesn't bother me too much. I am still investigating a more powerful new replacement, maybe the 16 or 20, but the space for the 2.8 reduction gearbox I want is very tight so it helps considerably if the engine is shorter. Nearer the C of G, too! I also rarely motor at more than 5 knots - I just open up with the Bukh to blow out the cobwebs every now and then. It's a good point that the 14 would be revving a lot higher than the Bukh - but maybe it would be rather quieter generally. The Bukh does thump a bit. The e-bay motor has the 2.8 reduction gearbox but it's still quite expensive and I noted the Marine enterprise, Dorset posting quite recently re second hand motors. Many thanks for all your helpful comments!

 

[nestawayboats]

It depends on what you want a (sailing) boat's motor to do. Wants are not necessarily the same as needs.

As a child (~50 years ago) we had a WOD (Folkboat with a counter stern), approx 2 tonnes, fitted with a Stuart Turner 4hp petrol motor. That would be considered very underpowered now, but also and more significantly it was always something of a surprise if it started. Even when it did work it was at best an auxiliary, so for the most part we sailed everywhere and we very definitely had to get up at whatever time was necessary to go with the tide. Or timed such that the tide would be in our favour at the most crucial point in the voyage (eg headland with tide race).

Motoring directly to windward against a full-flow Spring tide was simply not an option, you would go backwards. And then the Stuart Turner would overheat. I don't think we were that unusual, at the time. Nowadays you do see lots of yachts motoring directly to windward against full-flow Spring tides; it's definitely not efficient but it is possible with a large diesel engine.

I'm sure we'd have wanted a 1GM10 (single cylinder 10hp Yanmar) if we'd known what that was, but we didn't actually need it. It didn't stop us crossing the Channel etc.

50 years later I'm running around in a Sadler 29 with a 6kW electric pod motor... shock horror yes a 9m, 4 tonne, boat with only about 10hp (albeit much more low down torque/bigger prop than a 10hp diesel). Our limiting factor with that installation is more battery capacity than motor power, so (old habits die hard!) we're still making use of the tides and have the sails up as soon as there's the slightest puff of wind. 5 or even 6 knots is possible in a flat calm, but 4 knots increases the range massively (to about 60nm). It still doesn't stop us making cross-Channel voyages, and it's a lot quieter/ more reliable than a Stuart Turner

 

[Blueboatman]

My Seal 28 is from 1977 so RCD doesn't bother me too much. I am still investigating a more powerful new replacement, maybe the 16 or 20, but the space for the 2.8 reduction gearbox I want is very tight so it helps considerably if the engine is shorter. Nearer the C of G, too! I also rarely motor at more than 5 knots - I just open up with the Bukh to blow out the cobwebs every now and then. It's a good point that the 14 would be revving a lot higher than the Bukh - but maybe it would be rather quieter generally. The Bukh does thump a bit. The e-bay motor has the 2.8 reduction gearbox but it's still quite expensive and I noted the Marine enterprise, Dorset posting quite recently re second hand motors. Many thanks for all your helpful comments!

good luck

There’s a very good range of wise counsel posted.

And I’m delighted you mention one poor chaps sub optimal experience buying ‘ refurbished’ unseen

 

[colind3782]

Our Furia 332 originally came with a three cylinder 27HP engine which would be perfectly adequate. However, a previous owner decided that "bigger is better" and fitted a four cylinder 31HP Sole Mini 34. The result is that there is hardly any room in the engine bay making maintenance awkward, a bracket on the end has already worn a hole in the woodwork, and it's way overpowered.

 

[Tranona]

I have no particular opinion on this particular fit, except that I'm very much of the "auxiliary engine" camp.

What I do wonder with those advocating larger engines than those that were deemed sufficient by their designers... how does that tally with diesels generally preferring to be run hard? I'm surprised we don't hear more about glazed bores and the likes from under stressed larger engines

Older boat designers had a much more constrained choice of engines as well as lower expectations of motoring performance. The Vancouver 28 mentioned earlier which displaces 4.5 tonnes or so needs 20 hp at the propeller to achieve its hull speed. At the time it was designed the choice of engines was a 2GM which was rated at 16hp (even though that later grew to 18 - but called a 2GM 20!) a Volvo 2002 rated at 18hp or a Bukh 20. Only the last would achieve hull speed but was bulky and heavy. The next size up were 28hp Volvo or Yanmar both 3 cylinders which were far too big, both power and physically. The Yanmar was smallest, lightest and cheapest so was often chosen for this displacement range even though it was underpowered. there are many other boats (Sadler 29 and 32, Westerly Fulmar as examples that fell in a similar gap.

The introduction of the Japanese based engines (Beta, Nanni, Vetus, Volvo/Perkins) in the 1990s altered this by a wider range of sizes (10, 14, 16, 20, 25, 30) which enabled designers and particularly re-engine projects to optimise power in relation to the individual boat. Not only that they are mostly lighter and smaller than older engines. As to running hard, the usage pattern advocated in post#17 is a sure way of killing a small diesel, not necessarily bore glazing which comes from long periods of light load running such as charging batteries or motorsailing, but coking up valves and exhausts because the engine never truly gets hot or runs hard enough to fully burn fuel.

As I suggested earlier these newer engines should be specified and propped to run continuously at 50% power and preferably run for long enough to get hot than periodically run for short periods at close to maximum revs. You often hear of engines requiring new exhaust elbows or head overhauls at less than 1000 hours (10+ years for a typical weekend sailor). This can be avoided by following the simple rules. As an example my charter Bavaria with a Volvo 2030 did around 300 hours a year, mostly in 3-4 hour passages at 2400 rpm and when I sold it had 3300 hours still on its original exhaust elbow and running as well as it did when new. In that sort of use one would expect a life of 8000 hours.

My view is that re-engining it makes sense to choose the engine that gives the boat hull speed. There is little or no weight or size penalty between the 10hp and 16hp, between the 20 and 25 or 25 and 30. There is no impact on fuel consumption in choosing a larger rather than a marginal size because the horsepower demanded for a given speed is the same, although the revs will be lower. My current boat requires 27hp to achieve hull speed so between the 25 and 30. I chose the 30 and propped it to a maximum of 3300 (rather than 3600) and cruising speed of 5.5 knots at 2200 rather than 2400 for the 25.

 

[Snowgoose-1]

I suppose modern sailing demands being able to sail to a schedule with the engine taking care of any shortfall . Whether this is a good thing I don't know.

In my case. I'm about 7 nm from the open sea. Punching a 1kn tide and still being able to maintain 5kts over the ground in a small bost is certainly attractive. Particularly if you had to go to work for a living

 

[Laminar Flow]

The general approach to the matter is to determine the horse power necessary to drive the boat to hull speed and then add another 30% to account for adverse conditions. In practice, this seems to provide good results.

To reach hull speed, you need 1 hp at the prop for every 500 lbs of (actual) displacement. At the prop means one has to take into account that there is about a 4% loss in power for transmission and bearings.
With a nominal displacement of 3200 lbs, the Seal would need 14 hp at the prop, meaning that Tranona's assessment of 16 hp is spot on. Add to that your 30% and you are looking at round abouts 20 hp for this boat.

Contemporary engines are considerably lighter than what was formally available. In the 70ies a 100hp engine weighed in at around 700 kg. Today, you can get the same power out of one that weighs less than a 100 kg and is considerably smaller to boot.

For those wishing to indulge in horse power asceticism, or some sense of misplaced nostalgia: is it possible to get by with a smaller engine? Well, sure, but it doesn't really reflect the current realities of coastal cruising, particularly in tidal waters.

I'm not sure why people think that long distance cruising requires max power? Compared to the distances covered, one does surprisingly little motoring. Providing one has enough power to maintain 5 kn min. in the Panama canal and get yourself in and out of port, one could probably get by with a lot less.

However, that approach does not reflect contemporary life, and having to work around tidal restrictions and limitations within our busy schedules. Regardless, sufficient power is also a matter of safety.

Cruising speed is a question of fuel consumption and general wear and tear on the engine. I would say that 5 kn is probably about right for this particular boat and towards the upper end of economical operation.

 

[LittleSister]

I think 14 hp would be adequate, and rarely, if ever, a serious constraint.

I disagree that losing the last 0.3 knots (was it?) of the theoretical max speed will put you in danger. You are already constrained in a strong adverse tidal flow by the limitations of your waterline length, so you naturally just don't attempt to motor against adverse tides faster than your actually effective maximum speeds, whatever your motor. (We once battled out of the River Ore against incoming spring tide (in order to gain hours of tidal and daylight advantage later in the trip), moment to moment alternatively just holding our position over the ground or creeping forward very slowly. (That, as it happens, was with a Beta 14 - great engine - but amply powerful in a 23 footer, so our length was the speed constraint.) We wouldn't have attempted the same against, say, the faster Channel Islands races, though that didn't stop us cruising the Channel Islands.)

An alternative approach would be to replace the old Bukh 20 with a Bukh 24, a later, very similar weight somewhat different engine (though sharing quite a few parts with the DV10 & 20), still in production today, which is I am told, a fairly straight swap . This would not give you the weight reduction advantage of the switch to a Beta. On the other hand, these are relatively readily available second-hand (prices new are eye-watering!) as they are very commonly used in lifeboats, where typically they would have very low engine hours but should have had regular basic servicing, and are supposedly removed when the lifeboats are scrapped (presumably as being time expired or host ship scrapped?).

I, too, would be wary of a second-hand Beta. It is a modern era engine, most unlikely to have been fitted undersized. Why would anyone be changing it if it didn't have problems?


P. S. Someone mentioned losing speed as the season progresses, due to fouling. I have that on my current boat, and and it ain't due to an undersized engine - that is with a way oversized Bukh 36hp in a 27 footer, as opposed to the standard fitment Bukh 20hp.

 

[PetiteFleur]

Check before you buy another engine that it has the same prop rotation and g/box ratio - you may have to change them and other items. When I re-engined my Moody 33 from a Thornycroft 35 to a Beta 25hp, the prop rotation was different, silencer and exhaust on opposite side, new engine bearers etc. Beta service is excellent and spares are not as expensive as other brands.

 

[seeSimon]

I don't think the question is whether a 20 HP would be better than a 14 HP, it is whether a 14 HP, which is available, would be sufficient. If the OP is considering a world-girdling cruise, then the answer is no. If his cruising is family trips not too far from home then I suggest it is perfectly adequate.

Yes, this.

Imho (as owner of a 10 yo 26ft Swallow BC, considerably lighter? <2.5t, probably more easily driven, and fitted with a Beta 14 from new, by yard) a 14 hp beta is probably adequate.
How "cheap" is the one being considered?

Mine has a 2 blade gori folding prop on twin disc saildrive.

Sometimes I wish my boat had the 20hp, when filled with family/cruising junk, liferaft, dinghy etc etc...

But whilst a 20 probably better? No mention of a 20 being "on offer"?

 

[Ian_Edwards]

I had a Parker 275 for 13 years with a factory fitted Yanmar 1GM10 driving a 2 bladed Autoprop.
It certainly wasn't over powered, but in optimal condition would drive the boat at 6 knots.
It was quiet adequate for sailing around the NE of Scotland and Orkney.
The Parker and Seal are closely related and my Parker sailed really well. The engine was only used to get into and out of harbours or getting home in flat calm.
A 14bhp engine will work fine, if fitted with a decent prop'.

 

[johnphilip]

Don't forget to get the best prop, this can make a world of difference, particularly when motoring into wind and a chop. Our 33' Elan with a Volvo 18hp was under powered in those conditions but changing from the original Volvo 2 blade folder to a Flex-o-fold one transformed the performance in bad conditions. An old German comparative test I was sent gave the bollard pull with the Flex-o-fold as 30% higher.
I may be able to find it if you are interested.