How much horsepower??

[chowdan]

My boat is 16 tons unloaded and we have a 75hp.

We have enough power in any weather we've encountered and if need be will fly sails to gain extra momentum

[a64pilot]

The variable pitch props will only show an advantage when loads change significantly as in motor sailing, or when driving into the wind and waves hard.

However remember the discussion with the Triskel generator? It’s main selling point seemed to be that the average boat / engine combo had the engine significantly underloaded when motoring, and he said that had the motor operating inefficiently.
Well with an adjustable prop that wouldn’t be true as you would by using a pyrometer or ideally a torque meter adjust the load so that the engine was always properly loaded.
I believe the main advantage of that would be reduce cruise RPM and therefore noise and wear to a small extent. I don’t think it’s going to save a whole lot of fuel, my Swag is in the 10% area, perhaps a little higher.

A boat would be like an airplane, if you have an adjustable prop, your airplane can climb very well, but also increase pitch significantly so that it can fly fast too, normally without an adjustable prop you pick something in the middle.

[lifeofreilly57]

We have a 20 ton boat with s 4108, which claims to have 50 hp but is probably closer to 40 how.
Powering into chop and wind is slow and painful at times but still good enough to get where we need to. Fortunately the boat sails well.
If I had my druthers I'd have something closer to 85 hp in a boat this size. Not so much for long motoring periods but for getting in and out of tricky harbor entrances. A couple of difficult entrances would have been less butt puckering with that extra boost of power at the right time.
When we refit the boat we could have gone to a bigger engine but I decided to rebuild the original 4108 instead.
It's a mechanical motor with no electronics to fail and stone dependable.
Sometimes thats enough.

[Dockhead]

Originally Posted by a64pilot

. . . Well with an adjustable prop that wouldn’t be true as you would by using a pyrometer or ideally a torque meter adjust the load so that the engine was always properly loaded.
I believe the main advantage of that would be reduce cruise RPM and therefore noise and wear to a small extent. I don’t think it’s going to save a whole lot of fuel, my Swag is in the 10% area, perhaps a little higher.
. . .

Why guess? Just look at a fuel map.


I agree with you and I don't think the fuel saving is anything anyone would notice all that much. Maybe 10% or 15% at most and only in ideal conditions.



I think the big advantage of variable pitch prop is noise -- a really big deal on a sailboat, greatly improving the pleasure of being underway with the engine running, especially motor sailing. And without doubt the engine will be better loaded, turning more slowly, and so working in a more healthy regime, so most likely will last longer, maybe a lot longer.


But the advantage when motor sailing is so tremendous that in my opinion this justifies the Autoprop all by itself.



Now a CONTROLLABLE pitch prop like a Hundested would have additional benefits. Like for example being able to go really slow during docking maneuvers, by using a fine pitch. The Autoprop sucks here -- pitches up whether you want it to or not, so with a fairly slick hull like mine it's hard to get below 3 knots even at idle, which complicates docking maneuvers, requiring shifting in and out of gear.

[Dockhead]

Originally Posted by lifeofreilly57

We have a 20 ton boat with s 4108, which claims to have 50 hp but is probably closer to 40 how.
Powering into chop and wind is slow and painful at times but still good enough to get where we need to. Fortunately the boat sails well.
If I had my druthers I'd have something closer to 85 hp in a boat this size. Not so much for long motoring periods but for getting in and out of tricky harbor entrances. A couple of difficult entrances would have been less butt puckering with that extra boost of power at the right time.
When we refit the boat we could have gone to a bigger engine but I decided to rebuild the original 4108 instead.
It's a mechanical motor with no electronics to fail and stone dependable.
Sometimes thats enough.

Yep, that's when you need the power. And sometimes REALLY need it, even if it's only for a few minutes.


I had a 4108 in my last boat, which was not overpowered in a 10 ton boat. I can imagine in 20 tons you might be wishing for more.


Great engine, though, reliable as a brick. I think we had 20 000 hours on it when we sold it, and the head had never been off it, and it still ran like a top. Had to keep diapers underneath it, however.

[bbrasf5442]

3 hp per 1000 lbs for a full displacement hull will give you hull speed in all except the most severe conditions.

[ebsail]

Yup- 3 HP per ton is OK.. I drive an Oday 25 (4800 lbs dry). at 5 K cruise with a 6 HP 4 cycle Tohatsu. Just a bit under 3 HP per ton. 8 HP would be better against a strong headwind but my previous 10 HP was overkill and used more than twice the fuel per hour

[desodave]

Many of those boats originally sold in the PNW were equipped with optional larger engines to deal with our ocean currents. Our H38 has the larger 40hp Yanmar which gives it approx 2hp/1000 lbs. While you transit passes at slack, getting to them often involves a few miles of slogging against a significant current. To the OP's original point - the standard 28hp engine would be undersized for these waters imo. I can have 6 miles of current (minus some time in the counter currents) to deal with returning to our marina when I can't time the ebb - not sure I'd like it much with the smaller engine.

[ejjawhite]

Originally Posted by Wotname

The engine was considered an auxiliary power source; the principle power source was the wind.

No point in fitting anything bigger than the minimum required to move you around when there was no wind.

Back in the 80s, we sailed sailing boats and we motored motor boats. If the wind was on the nose, we tacked upwind or waited for better weather or changed our destination to somewhere downwind.

Not saying it was better or worse, it was just the way things were done when sailing in the 80s.

OK, so I have a 1983 Cal 35 which came w a 32 HP Universal. During a refit in the mid 90’s a Yanmar 30 HP ( 3 HM35F) replaces it. I found it fine with the original 3 blade fixed prop except for in a 3’ or higher chop. When I installed a 3 blade AutoProp (bought used and rebuilt myself for a total of $1000) this eliminated the problem of powering through waves to a huge degree, as that prop design is always pushing straight ahead, not at the angle which the shaft exits the hull. That angle increases substantially as the bow lifts. Same with wakes. When a 3-4 foot power boat wake would cut my speed in half, now I don’t even lose a knot. That being said, I wouldn’t mind another 5 HP or so, but using less than 1/2 gallon per hour in most conditions. Of course heading up wind and up current/tide in 10-3 foot waves I usually can still make about 4 knots at 2200 rpm.

[MJH]

Originally Posted by geoleo

Been looking at some used Catalina s /Hunters most are 1980 s -90 s . 36footers 35.5ers . Im surprised that they were equipted with suchlow powered engines I see a 198 C36 with a 21 HP and others similar with 23HP. These are 6-8 ton boats and they must not go hull speed in a 3ft chop+ anyway I don't like to run any engine for extended hours at top speed... What gives here???

I remember when the standard was 2-3 HP/1,000 displacement. My neighbor had a Columbia 50 (32,000lb.) for racing; Vic-Maui, Swiftsure. In addition to some hull/rudder modifications the boat only had a 30-35HP diesel to save weight.

Most cruisers are in a hurry to get to their destination these days and don't have the patience.

~ ~ _/) ~ ~ MJH

[jrau18]

One thing I havent seen mentioned is weight. Sailboats (as opposed to motorsailers) are built for sailing performance first. Doubling the HP meant doubling the weight, and it isnt adding the weight way down in the keel where you might be able to use it to advantage.

New production sailboats are built with the same idea. But engine technology is so much better (plus turbos are more prevalent), the same weight of engine might have 2 to 3 times as much horsepower. So the compromise isnt as.... compromising? You can have motorsailing power in a well sailing hull.

In theory, you could do this upgrade on a 60s/70s/80s boat, but you'd need to think about strengthening the rails, etc.

In practice, as many posts pointed out, most of us who are cruising dont feel a "need" for more power. Shoot, many of us have continued cruising after the aux engine died for months, or even years. I know I have, I preferred continuing to cruise and have fun over taking the time to fix the engine in an inconvenient third world country. I fixed it later in a more convenient location.

Would I turn my nose up at more power with no weight penalty? No, of course not. But for the sailing I do, it's not on my priority list, either for time or money.

Nothing wrong with people wanting lots of engine power in their sailboat, but different people use their boats differently.

[GordMay]

Greetings and belated welcome aboard the CF, bbrasf.

[Mauruuru]

I had a 1970 30' Oday that had a 12 HP Yanmar engine. That boat weighed 10 tons. My current boat weighs under 8 tons fully laden and has a Yanmar 30HP engine......I prefer the larger HP especially in a blow or bad current situation......

[Wotname]

I don't understand how extra horsepower can help in a adverse current!

If you can reach hull speed, then how does more horsepower overcome a foul current?

Yes, it can help in chop, wake and wind because all of these add drag to the boat and more horsepower will overcome the extra drag and return you to hull speed but current does not (by itself) add drag.

[Dockhead]

You're absolutely right, of course. We sail - and motor - in water. Current is irrelevant.

Originally Posted by Wotname

I don't understand how extra horsepower can help in a adverse current!

If you can reach hull speed, then how does more horsepower overcome a foul current?

Yes, it can help in chop, wake and wind because all of these add drag to the boat and more horsepower will overcome the extra drag and return you to hull speed but current does not (by itself) add drag.