repowering my sailboat- engine selection

[Scaramanga F25]

$ 1000 boat, get a used $1000 engine.

[Bawlmer]

Agree with Ted. My 270 has a 18 HP Westerbeke and it pushes it along just fine. You definitely do not want to underpower your boat, specially in an area with strong tides and currents.

It still would be way easier to sell what you have and buy a diesel powered model. Plenty of them out there.

[hamburking]

I've owned and sailed several boats in that size/weight.
I'd suggest a yanmar single cylinder.

A newish yanmar 1gm would be perfect, but an older YSM would also be great, and potentially save you some dollars. These engines are extremely reliable and robust...they have very few moving parts!

Your late model catalina is a smallish boat. You don't want to overload it with a huge diesel. Key to getting the boat to move with your new diesel is having the right prop and reduction ratio.

[fish53]

I took the old 13hp Volvo out of my Cape Dory 28 and replaced it with a Kubota D1005 that I marinized myself. I set the fuel at 21hp and put on a three blade propeller and now it stops when I engage reverse and goes at hull speed without much effort.

[PEACETIME]

You mentioned making a "killer profit" on your past boats. If that is of high importance to you, then by all means install a diesel. For simple boating I would install a newer 15 - 20 hp 4 stroke outboard. You could use a bracket or jack plate to get the prop out of the water while sailing. There are trade offs with both , the space lost to an inboard with fuel tank or the inability to heat water with an outboard.

[thomm225]

Originally Posted by PEACETIME

You mentioned making a "killer profit" on your past boats. If that is of high importance to you, then by all means install a diesel. For simple boating I would install a newer 15 - 20 hp 4 stroke outboard. You could use a bracket or jack plate to get the prop out of the water while sailing. There are trade offs with both , the space lost to an inboard with fuel tank or the inability to heat water with an outboard.

A 15-20 HP outboard is way too much for a Catalina 27. Most folks go a bit high with an 8 hp or a 9.9 hp.

Plus a heavy 15-20 hp four stroke outboard on the stern will have the bow pointing out of the water. It's too much weight on the stern.

My 5 hp 4 stroke weighs 58 lbs and works out pretty well, but I'm used to no power since my first 4 sailboats (beach cats) had no power but I still competed with them in multiple 30-100 mile races over a 15 year period.

I paid $1500 for my new 2011 outboard after the original diesel on my $2,000 boat failed and the $1,300 replacement diesel failed. The 5 hp outboard pushes the boat just about the same as both the old diesels did and with no bad smell or leaks into the boat

[roverhi]

Just to be the umteenth person to bring up this simple fact, a ton of hp will not make bucking a current any easier. The exception is if your powering into a headwind and/or seas. Even then, there is a limit what extra hp will get you. A 7 knot hull speed sailboat will do just about 7 knots no matter how much hp you stuff into it. If your faced with an 8 not current you are going to go backward at one knot no matter what.

I'm sure there may be some conditions where you'll be able to take advantage of too large an engine but they are few and far between. For the most part a smaller engine will do just fine. Besides, if the wind is blowing I'm sailing. If I want to go somewhere where the wind makes it a tight sail, motosail. With the motor you can get close to 29 degrees off the relative wind and still make good speed through the water. Did that very occasionally on our W32 with the 25hp Volvo when the wind was tight on the nose.

As far as 20hp in a Cat. 27, it's more hp than you'll probably ever need but it's not grossly oversize either for HP, Foot Print or weight. As a mechanic you probably have your choice of engines to rebuild so look for the one with at least 15hp that will have cheapest parts cost for the rebuild.

[fish53]

Originally Posted by roverhi

Just to be the umteenth person to bring up this simple fact, a ton of hp will not make bucking a current any easier. The exception is if your powering into a headwind and/or seas. Even then, there is a limit what extra hp will get you. A 7 knot hull speed sailboat will do just about 7 knots no matter how much hp you stuff into it. If your faced with an 8 not current you are going to go backward at one knot no matter what.

I'm sure there may be some conditions where you'll be able to take advantage of too large an engine but they are few and far between. For the most part a smaller engine will do just fine. Besides, if the wind is blowing I'm sailing. If I want to go somewhere where the wind makes it a tight sail, motosail. With the motor you can get close to 29 degrees off the relative wind and still make good speed through the water. Did that very occasionally on our W32 with the 25hp Volvo when the wind was tight on the nose.

As far as 20hp in a Cat. 27, it's more hp than you'll probably ever need but it's not grossly oversize either for HP, Foot Print or weight. As a mechanic you probably have your choice of engines to rebuild so look for the one with at least 15hp that will have cheapest parts cost for the rebuild.

You apparently don't spend much time in Maine or Atlantic Canada where the tide can be quite fierce in numerous places. You are correct about parts, my Kubota is a common tractor engine and tractor dealer prices are half what marine places charge.

[Scrimshaw4]

The BETA engines are an excellent choice and I'd recommend the BETA 20 diesel. The key factors to be dealt with will be creating an engine bed that will line up with the shaft log that you will have to construct as well as the shaft strut that you will also need to install. All of these items need to be incorporated with additional reinforcement glass / resin work. Pay particular attention to the rudder offset angle as well to counter prop torque. You might be able to get the dimensions from Catalina or through the Catalina Owners Association. Hope it all works out and that the hull and deck are solid.
PS. In my opinion, Sherwin-Williams makes the best barrier coat and you can get it thru your local S-W store.

[fish53]

Originally Posted by Scrimshaw4

The BETA engines are an excellent choice and I'd recommend the BETA 20 diesel. The key factors to be dealt with will be creating an engine bed that will line up with the shaft log that you will have to construct as well as the shaft strut that you will also need to install. All of these items need to be incorporated with additional reinforcement glass / resin work. Pay particular attention to the rudder offset angle as well to counter prop torque. You might be able to get the dimensions from Catalina or through the Catalina Owners Association. Hope it all works out and that the hull and deck are solid.
PS. In my opinion, Sherwin-Williams makes the best barrier coat and you can get it thru your local S-W store.

I don't know about spending ten to twelve thousand on a Beta to put in a one thousand dollar boat, at least not until the restoration is well along as these things sometimes don't approach completion. There are cheaper alternatives to "marine engines" that are really simply tractor engines with a few marine accessories, but you do need to enjoy that sort of thing.

[Mike Banks]

You do not have to hack anything. Fit a pantograph OB mount--that will allow you to wind it up to above deck level THEN tip it backwards out of the water.

Outboards beat the heck out of inboards for small vessels, and when it is hoisted it can be covered with a waterproof bag.

Fitting a diesel engine to one designed for an outboard without further extensive and expensive modifications is asking for a damaged hull and possibly a foundered vessel.

There would be a lot of work strengthening the hull to handle the weight and torque, then the design and fitting of engine mounts, the provision of extra in hull as well as outer hull for support for a skeg or extension to the keel, stern tube and seal as well as shaft and folding propeller.

Nah. Just get a pantograph mount with nice polyurethane buffers, and use a quality four stroke outboard.
.

[roland stockham]

You are falling into a very common trap with engine sizing by starting at the wrong end! Start with the prop not the engine. What size prop do you want to fit? Larger slower turning props are more efficient but create more drag and the combination of size and speed determines how much power they can absorb. If you increase engine size without increasing the prop you just loose efficiency and create cavitation.
The other trap is thinking that more power equals higher speed. Once up to about 1.4 x root WLL doubling power will increase speed by less than 1kn but that is always speed through the water not over the ground. Increasing engine size does next to nothing to 'punch' through a tide, your speed over the ground is still water speed less tide.
What bigger engines do s allow you to maintain hull speed against more load. 2hp per ton will happily get hull speed on flat water with no wind but motoring into 20kn with some waves you run out of power. This is a double whammy because once the engine runs out of power it can no longer drive the prop at design speed and slows down producing less power. Effectively it stalls. Running the engine in this state for any length of time will destroy it.
So you need to decide what you want the engine for;
true auxiliary to get in and out of habour and make progress in calms 2hp/t or less
Using the engine to drive the boat in moderate conditions into wind as an alternative to sailing 3hp/t
Having an engine as part of storm tactics and being able to motor to windward in a gale (obviously not at hull speed but without overload) 4hp/t
But start the calcs by working out what prop you need then select an engine to drive it.

[thomm225]

Even on my 6600 lb displacement full keel sailboat with it's 5 hp outboard, I rarely run the engine full throttle because the boat will move no faster than it does at about 2/3rd's throttle.

My boat will cruise along in calm water at about 5 knots with my 5 hp 4 stroke
25" shaft outboard with standard prop.

[Kudu]

Repowering an old boat which has an existing diesel is already a poor investment decision, unless you plan to keep the boat for say 10years, and it is a very special boat.

When it is an original outboard boat, you are going to add a lot of work in mods and cost for shaft, prop, sterntube, bearers, fuel tank, and the list goes on. IMHO just crazy.

Remember that an outboard can work with a nice clean prop if you have a system to store it out of the water when on the mooring. An inboard usually has some degree of prop fouling, which can wreck the efficiency and chew up a big chunk of the power from the engine.

Well mounted o/b is good, you can get to the motor easily if you have a problem. The prop usually stays in the water in choppy seas. Modern 4 strokes are reliable and less sensitive to periods of disuse. Rigging something to lift the motor out of the water is not hard for someone with a bit of mechanical skills.

[valhalla360]

Something doesn't make sense with this post:
- Experienced diesel mechanic.
- Has rebuilt multiple boats.
- No indication of a problem with the outboard.
- Complains about the complications of modifying for the outboard...but suggests a drastically more complicated set of modifications to accommodate a diesel.

Asking very simplistic questions that someone with that experience should already know.

Even if the labor is free (and your time really does have value), it makes no sense to swap out a perfectly functional outboard in this case.