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Old 06-06-2015, 23:00   #1
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Outboards vs. Diesel I/O

I am looking to change out a Volvo diesel I/O with hopefully a pair of Yamaha outboards for several reasons. First, I am done spending thousands and thousands of dollars from constant motor and OD problems with this diesel. It has been a nightmare. I live in Englewood Florida and you have three choices when it comes to acquiring any type of service. Mattos marine in Ft. Myers, Suncoast Diesel in Sarasota and Blue water marine repair in St. Pete. All of which are a hour or more away. And come spring time, you can forget about getting one of these guys to come out and work on your motor, unless you dont mind waiting for up to two months. This particular diesel is a 2004 Volvo KAD 44p-c. 260 hp driving a Volvo DPE 1.68 duo prop outdrive. The motor weighs 1268lbs which is a lot of weight. And the 260hp is not enough for my 29' Sport Cabin C Hawk. Long story short, I'm done wasting any more time waiting along with funneling tons of money keeping this POS running! Especially when fishing season is waiting too! So I need to ask what kind of HP from the outboards will I need to surpass the torque of the diesel and give me a faster cruise with more power? I know I am probably going to have to beef up the transom but how do you tell what will be needed there to support the outboard bracket and the two motors? Maybe a pair of 150's? THANK YOU in advance for any help here.
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Old 07-06-2015, 21:54   #2
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Re: Outboards vs. Diesel I/O

Bracketing I/O hulls is popular with older boats to get rid of the engine compartment and regain lost cockpit space. You will need to strengthen the transom as a bracket with outboard engines of any size will put new and heavy loads on a transom which was designed only to carry the load of an I/O unit and not the engine weight which is supported by the internal stringers.
See if there is an owner's site for your boat to see if others have made the conversion. You will have to change a lot of components to make a successful changeover: Steering, instruments, fuel supply, wiring etc.
Good luck.

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Old 19-07-2015, 19:40   #3
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Re: Outboards vs. Diesel I/O


I had one 24' Sealine with a single KAD 32 and a 30' Fairline with twins, they are annoying engines as the compressors have several electrical gadgets that seem to fail, I now have a 24' centre console with a 250hp yamaha, but it is a very different beast

Buy a different Boat that was designed for that power With the outboards on it , the work involved is never going to be feasible to convert from inboard to twin ob's,
$ 30'000 for new units will only be the small end of your costs, as you also have to look at who is going to buy a boat that has changed it's designed power configuration

I would say you are looking at two 350hp yamaha's if she is heavy, it's like saying how many motor bike engines do I need to make my 40mph tractor more reliable

I should add that the yamaha with the lifting overhead cam is a very good unit, but they are what they are, a very different unit to a Compressed turbo diesel

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