Thread: Twin or Single screw

In 1972 I finished off a Hartley 14.5' outboard powered runabout. I discussed outboards engines with a retail supplier. His advice was simple 2 outboards were twice as much trouble and double the drag. I took his advice and bought a single 55 HP engine in lieu of two 30 HP and later bought a 4 HP aux to get me home if I needed it. I did not regret the decision.
Whitewood

On larger craft, twin setups are a dream to maneuver. If you've ever had some straight shaft experience you can understand how difficult it can be to dock, in a contrary wind and/or current. Twins solve this issue, offering unmatched maneuverability. You can even hold "station" in a current, which you can't in a single equipped boat.


They also are an added complication and contrivance with double everything.

On the other had, you can limp home on a single engine if the other takes a dump.

On small boats, I wouldn't recommended them, but on larger craft (say 25' or more) then multiple engines can solve a lot of problems.

This said, I have an 18' hardtop runabout that has two 30's on it's butt, rather then a single 60. The single would be lighter and offer more power, but the twins just look so good and sound even better.

The before and after pictures are below.

Richard, does that mean the 19' version is bigger all round?
I mean the same design elongated (maybe stretched between stations) wouldn't theoretically need more power would it, except that it may have a higher potential hull speed, off-set somewhat by more weight? (shoot me down in flames here, I'm hoping for clarification, not giving technical advice!)

But if he has redesigned bigger and heavier with twin bathrooms and a pool table and you are needing a big power plant, that's getting away from what attracted you to the boat isn't it? (Putt PuttPutt not vroomvroom vrooom)

I'd love to see it stretched a little, but it'll become a very bulky hull if it's scaled up. Good to see that the project has become a goer for the Winter.
Don't suppose we could see the new side view?

Originally Posted by rob540

Richard, does that mean the 19' version is bigger all round?
I mean the same design elongated (maybe stretched between stations) wouldn't theoretically need more power would it, except that it may have a higher potential hull speed, off-set somewhat by more weight? (shoot me down in flames here, I'm hoping for clarification, not giving technical advice!)

But if he has redesigned bigger and heavier with twin bathrooms and a pool table and you are needing a big power plant, that's getting away from what attracted you to the boat isn't it? (Putt PuttPutt not vroomvroom vrooom)

I'd love to see it stretched a little, but it'll become a very bulky hull if it's scaled up. Good to see that the project has become a goer for the Winter.
Don't suppose we could see the new side view?

well Rob i have printed of both the 16 and 19ft versions to the same scale an sat one on top the other and held them up to the window, there are a few very slight differences to the shape of the hull, mainly at the stern where it is a little narrower and has a slightly deeper V below the water line, the beam has only increased by 2" to 7ft 2in, she still only draws 18" and is no higher in profile, basicly to my un-trained eye she has just been stretched a bit. and if anything she looks more streamlined than bulky, she will be heavyer as the hull is 1/2 ply and not 3/8 as the 16footer.

as for the Putt PuttPutt not vroomvroom vrooom she is still a Putt PuttPutt if powered by twin 8hp's well to me she is anyway

i will have to contact Sam Devlin to see if it is OK to post a pic of the side profile as i'm the first person to have seen this new design.

Well mate, that sounds just what you need, and if they are only 8hp's it would make sense to me to have a pair because of the emergency benefit of the extra engine.

well i have had the OK from Mr Devlin to post the PDF's so here they are

Very attractive Richard. Looks even better than the original and certainly more roomy. Only one bathroom though.
I'd love to make one of those! But I'd need to have a mooring and that means endless cost and misery here.

that's the boat i have looking for Rob

lucky for me the bay where she will be moored is free, but can only get insurance for the summer season and have to take her out the water over winter, so i may consider putting her in one of the marinas so i can use her all year round

here are a couple more with a flying deck on the same hull