Does anybody have a view on the relative merits of inboard diesel v outboard in a cockpit well. I am rather fond of the Tophat, but I struggle to locate one without the 'hole in the cockpit'. Am I limiting my search unnecessarily? The mission profile is coastal single-handing up and down the east coast, with the occasional foray into the Sols and West Papua.
Select to expand quoteLazyjack said..
Does anybody have a view on the relative merits of inboard diesel v outboard in a cockpit well. I am rather fond of the Tophat, but I struggle to locate one without the 'hole in the cockpit'. Am I limiting my search unnecessarily? The mission profile is coastal single-handing up and down the east coast, with the occasional foray into the Sols and West Papua.
I sailed my dad's folkboat a lot many years ago which had an outboard in a well in the lazarette situation.
There was a fibreglass plug that went in the well when you pulled the outboard out but it was a bit of a mission getting the 8hp outboard out and laid in the lazarette. I didn't like sailing with it in because obviously it created a lot of drag also evidenced by gurgling from the well.
Looks like the inboard Tophat has the propeller in between the keel and the rudder so the rudder would work a lot better under power. Obviously in rough seas the prop location of the inboard is unlikely to ever cavitate which the outboard probably would.
The only plus for outboards is ease of maintenance and replacement when they go wrong.
Select to expand quoteLazyjack said..
Does anybody have a view on the relative merits of inboard diesel v outboard in a cockpit well. I am rather fond of the Tophat, but I struggle to locate one without the 'hole in the cockpit'. Am I limiting my search unnecessarily? The mission profile is coastal single-handing up and down the east coast, with the occasional foray into the Sols and West Papua.
Having done a little sailing on a mate's tophat with the outboard in the well and then on his next boat of a similar size with an inboard diesel, I would go the diesel. 
Select to expand quoteGiven the pros and cons it probably doesn't matter. A modern 4 stroke outboard is pretty nice.
Possibilities had a two stroke yamaha 8 and he sailed the world.
Select to expand quoteDoes anybody have a view on the relative merits of inboard diesel v outboard in a cockpit well.
For equal boats, the one with the diesel will cost more upfront. It will have better fuel economy, and the propeller will grip the water better in rough seas. Easier to generate electricity.
In favour of the OB well option: you will have enormous internal space for water, chain, and spare parts. With the OB raised you will have zero prop drag, hence faster sailing. The boat will be at least 80kg lighter (engine and starter battery), so you could add that weight back in chain, water, food, etc. Easier to service the motor and easier to take it to a mechanic rather than wait for mech to visit you. Easier access to OB motor, rather than a diesel in confined spaces. Easier to un-tangle weed or ropes from the propeller.
A tilting OB eliminates the need to lift the motor out each time. For me, upfront cost, fuel economy, storage space & weight were the biggest issues. My diesel motor died, was too expensive to replace, so I installed an OB well, with the OB tilting so I don't have to lift it out.
8-10 HP diesel will use 1 L/hr for 5 kts/ 5 miles, whereas an OB will use about 2.5 - 3 L for the same 5 miles/ 5 kts.
Weight saving: 100kg diesel + 20kg starter battery versus 30-40kg OB, no separate starter battery.
The problem you will have is finding a boat with a newish diesel. Most will be pretty old and maybe not reliable for offshore work. The biggest drawback of an ob in the well is loss of cockpit space. The drag if you leave the ob in the well on passage is not too bad if you make a fairing plug. Certainly less than a fixed inboard. Risk of theft on a mooring if you don't have the strength to lift into the cabin.
I would put in a vote for a well thought out and built four stroke outboard well. There are quite a few sports boats that have a nice bent traveller arrangement that allows an outboard to be raised and put on the cockpit floor. Myself - I would probably copy the idea used by Schionning cats. Put a plate on the bottom of the outboard that matches the bottom of the well. Then use a simple gantry and tubing to raise the outboard stright up with a tackle (did this on my mums Contessa). So nice and clean for sailing and in the water in a second for motoring. My mate spent more doing a major service on his diesel than I spent on one motor. If you like sailing you will need a feathering prop. A new will cost more than a new Yammie 8 or 9.9 outboard. As for noise, I find a diesel much noisier than a Yammie four stroke, it thumps the boat less but it is harder to fit sound insulation around.
A great thing about outboards is that you can buy a new one every 5 years of so, and sell it, and pay less than getting a diesel serviced. Also, if anything goes wrong, you pull it off and take it home, or to the shop and that saves huge amounts of money.
My Yammie 25 is 18 years old and has been sterling all its life.
I've sailed both configuration Top Hats along the SE NSW coast.
The Mk1 Top Hat had an outboard mount on the transom. Mk2&3 have the outboard well. There are two inboard mounting systems, the one illustrated with prop in a rudder cut out, and the other with slightly offset prop which sits behind the rudder. Cost and maintenance issues, and difficulty finding one with a newish inboard have already been mentioned. In no wind or following wind exhaust from the cockpit well outboard's telltale hangs around the cockpit or is blown into the cabin, not dangerous but uncomfortable and can contribute to nausea.
I blew a Welch plug on my Volvo powered Top Hat and fitted a Honda 5HP OBM on the transom as a temporary fix. It was fine in still water but cavitated in even moderate conditions forcing me to stand off Batemans Bay overnight.
My next Top Hat will also be an inboard powered one.
I owned an Endeavour 24 with an outboard in a well {Volvo outboard} then a quarter tonner with and outboard on the stern. I would never contemplate either again unless it was a trailer sailer. There are two basic requirements for a comfortable offshore yacht. Standing headroom and an inboard diesel. The Tophat has standing headroom!
I've got a few thousand miles under my belt in a diesel powered Top Hat [Mk 1] and quiet a few in an outboard driven one. [Mk 2&3]
Fuel:
Twice as much required for an outboard.
Noise:
Highly recommend ear muffs with an outboard for long hour use.
Weight:
Comparable when fuel is added.
Space:
Not really an issue as area behind inboard has my batteries.
Power:
Hull speed is 6 1/4 knots and if an outboard cannot reach that speed or a bit higher in calm water
you will have to enter/exit areas with high current with that current.
I do know a 20hp inboard has been fitted to a TH but normally 10 hp is the go.
With outboards the room to fit means outboard size is limited to around 8-9hp depending on make.
Fitting an out board on a Mk 1 may allow a higher hp as its fitted on the stern.
Outboards will cavitate in any swell which means loss of way.
Cruising:
I prefer an inboard for coastal cruising but as others have said there are advantages and disadvantages
in having an outboard.
I suppose it comes down to personal choice and whats available, given the condition of any TH purchased.
And that may be the determining factor as most TH are 50 years old or older and with a good condition TH
with or without an inboard/outboard, the motor may not be the determining factor.
Phil.
See my Blog 'Sailing Seaka Solo' for my adventures.
sailingseaka.blogspot.com
Don't forget modern 4 stroke outboards use far less fuel than a 2 stroke. The fumes can be reduced by fitting a hose from the exhaust relief to just under the waterline. Makes starting a little harder, but also reduces the noise.
I appreciate the problems of those of you who have used outboards on yachts, I have suffered from them myself on badly designed two stroke systems. My take on it is that a well designed outboard system can deliver a really good solution for small yachts and multihulls. My own 38ft 4000kg cat has outboards on pivoting mounts that wind up and down from the cockpit. They are fab engines, offshore and inshore. Because I have built a few boats, I would have no issue with altering the outboard well, installing a slide above it and installing a Yamaha 8 or 9.9 four stroke (fab engines). Our outboards have motored us across Bass Strait, got us across bars, and allow the boat to sail really nicely. I wouldn't install twin diesels if you gave them to me for free. As for noise, when operating at medium revs the Yammies are pretty quiet, and don't make the boat thump.
There is a big difference between a two stroke plonked on the stern and a nicely designed mounting system for a high thrust Yamaha 4 stroke. I get that the diesel may win out in the end, but it should be compared to a well designed, inboard of the stern, easy to use, 4 stroke high thrust system.
My recommendation would be to use some ideas from the following system
schionningdesign.com/wp-content/uploads/2020/08/Outboard-Motor-Installation-Ross-McCombe-Part-2-Schionning-Designs.pdf
A cockpit system would not need the blower, it is the well that is the cool bit.
Select to expand quoteLazyjack said..
Does anybody have a view on the relative merits of inboard diesel v outboard in a cockpit well. I am rather fond of the Tophat, but I struggle to locate one without the 'hole in the cockpit'. Am I limiting my search unnecessarily? The mission profile is coastal single-handing up and down the east coast, with the occasional foray into the Sols and West Papua.
Depends a lot on what you find in your search for Tophats. There are some about with Vire inboard two stroke petrol engines. Often these will be stuffed and the owners have tacked an outboard on the stern. The Americans for years have run inboard petrol engines. There is no reason why a modern, 4 stroke full EFI engine could not replace an old Vire. People with outboards will often store their outboards on the cabin sole for safe keeping and don't worry about fumes settling in the bilge.
Check out the Atom voyages website. He has a great solution perfect for a Tophat
atomvoyages.com/
The Mk1 TH with outboard had a heavy/thick transom fit for purpose. I'm not sure if Mk1 with an inboard as original equipment had the same heavy transom. Mk2 & Mk3 have much thinner transoms needing reinforcing even for a 5hp OBM. Also, access to the transom inner side is very limited and without drilling access holes in through the rear cockpit, an OBM would have to be mounted to one side. Inboard fitted hulls don't have a well, so are not easily retrofitted to a well mounted OBM. Numerous TH owners have written about OBM size limits - mainly about OBM foot design variations between models and difficulty getting larger OBMs into the well - squeezing it in on an angle does not allow a vertices raising/lowering system. I'd guess there are limits to enlarging the well as the rudder shaft sits just in front of it.
Bottom line - look and measure carefully if you're buying a boat with plans to modify the OBM well.
Not TH specific, but with my lightish 28'er I went from a diesel to an outboard mounted on the stern, but retracting forward through the walk-through transom - the bracket was simply mounted on mainsheet travellers.
I wouldn't go back to a diesel. Even in howling conditions offshore (ie the boat had been badly overpowered with just a #4 headsail up) the extra-long shaft Tohatsu 9.8 2 stroke didn't cavitate, although it did once or twice in shorter powerboat waves or when motoring slowly offshore in swell. Having an engine large enough to drive the boat fast could be the key, because once you get to hull speed the large and high quarter wave immerses the engine another foot or so.
A diesel, even with folding prop, takes about 2% of speed under sail which doesn't sound much but is actually similar to having a 2' longer boat, or going from only having a small (105% overlap) headsail to having a big 150% overlap headsail. In my case, when I dumped the diesel I also dumped the big headsail which made the boat much more fun and much easier to sail.
Yes, the noise was different with the outboard but the lack of vibration made up for it. The fuel use was higher but the gain in interior storage more than compensated for it.
We had a similar result taking out the diesel from a 25ftr and replacing it with an outboard in a well and fitting it with a simple vertical retracting system, as noted by Kankama above.
While there are some very experienced people here who have very valid opinions against outboards, I'd say that the specific configuration of the particular boat is critical. Yes, a 5hp on the transom would be a complete PITA but something like a 9.8 with a well sorted retraction system can be a completely different issue.
My TH Mk2 runs a Yanmar diesel. it was looked after by the fastidious first owner and I continue to do the same as I am a farmer and well used to servicing diesels. Comments:
Hard to find a boat with such a good service history (and this could be a deal breaker for me).
Noone has mentioned handling; it is well known that the TH with a diesel is woeful to manouevre going astern (berthing).
Single cyl motor is underpowered - I would prefer more.
Having said that, I would still vote for the diesel option.
