Hi guys Im new to this forum As i can not find any data on the net regarding my current project Im after as much useful info as i can get in regards to installing outboards on to my brand new 53 ft fly bridge cruiser This vessel was originally designed for 700 hp twin screw application but never installed But due to the cost of purchasing the engine's and gearboxes and all the under water gear and then to have them installed in on my vessel in my location was not a viable option Thus my current position I have had the transom modified to accept up to 4 x outboards with centres set at 660 mm( but possibly can go wider) and 30 in legs The vessel has a semi displacement hull which has a 45 ft water line with 5.1 mt wide beam and a displacement of 24 tons if i went with the inboard installation But i will be reducing this by roughly 4 to 5 tons if i put 4 x outboards on Im just after some useful feedback as to the requirements and limitations i am going to face moving forward I thank you all in advace for your assistance
Your situation is reminiscent of another thread on YF... https://www.yachtforums.com/threads/mercury-outboard-powered-65-motoryacht-no-joke.16621/ ***
And that was a customer of mines, old boat before the current guy had rigged it with outboards.....LOLOLOL
Huckins built a 53 footer with outboard power for a client in the seventies, but she has since been converted to inboards. Best, Maldwin
I remember her. Had 4 OMC SeaDrives. It did run well. But remember, Ole Hucks have little deadrise and draft. Near a box with a point on one end.
That's a lot of weight to (re)move from the center of buoyancy/just aft of COB to WAY out back. I would speak to a naval engineer to do some calculations here. Now, HP for HP you would indeed save some weight here. In fact you could end up having to add ballast somewhere/move tanks forward. And, the sugar scoop on the back would probably have to have volume ie be a pod to provide some buoyancy. It is regularly done on smaller boats to free up space in the cockpit/remove PITA inboards/stern drives. Then there's the issue of vertical travel of the stern/swamping on a boat that would/could go on bigger water. Again this needs serious MATH. The laws of physics ALWAYS apply. So, to do it RIGHT may or may not be a savings over a conventional installation. Of course if you're extremely talented and have the tools you could do it cheaper. And then..... how would it look. But that's for another thread.
Thanks Oscarvan for your positive input My ship wright and i have already had this discussion about the distribution of weight As for hp diesel engines are rated at the flywheel and outboards are rated at the propeller as you would be aware We are going to gain some 350 to 400 hp over the conventional twin 700 hp inboard application if i went with 4 X 300 hp outboards And we all know how noisy those inboards can be at at W O T As this is a new build and we have a clean slate to work with We can add or move ballast around till we get the correct formula With the subject of swamping I dont think that will be an issue because we have redesigned the transom to accept 30 in legs buy increasing the height some 370 mm from where it was and created a well where the last platform / step use to be and installed 2in drain holes at each end to siphon away any backwash or water that may get onboard As the vessel was designed with plenty of freeboard at the transom to accept a platform / marlin board and two steps up to get to deck height we have only lost one step to accommodate the outboards We have a clean hull to start with as mentioned This is a new vessel and never seen water so we dont face the problem of patching up stern or rudder tubes or the task of removing and patching underwater gear and removing the engines and gearboxes I have enrolled the services of a first class Shipwright His work is exceptional and does not look like it is tacked on as some of the photos i have seen in reply to my post I am still keen to discuss and eager to listen to anyone with some positive input as we are still in the build stage
My ship wright and i have already had this discussion about the distribution of weight I'm sure he is a great guy. But you did not call him an marine architect.
Hi capt Ralf Thanks for your input I will make arrangements to meet with a navel architect to discuss the issue of weight distribution on my vessel As I have be dwelling on this for some time I did have a plan in mind to start with one half the weight of the inboard motors and all attachments as balast ( water in plastic 44 gallon drums ) just aft of mid ship and add or subtract as needed Now I will take your advice capt ralf and have words with ano architect prior to launching Again Thanks for your input