Inboard to outboard conversion

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Fluid Motion Model
C-242 C
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Pixie Lu
Is it practical to convert an inboard diesel to an outboard? I like working on my boat but working on the Yanmar seems especially difficult because you are working reaching down and a lot of it is completely inaccessible. Even minor repairs can be very difficult. That being said it seems like there could be a lot of issues in switching to an outboard:
1. Are there engineering hull design issues?
2. What about supporting the outboard on the stern?
3. What about the different systems that use water for cooling or heating?

The Yamaha outboard on another boat i have is 16 years old and has never needed any significant repair after several thousand hours or more. It is relatively quiet and efficient. It starts immediately every time.

Any thoughts on this from anyone?
 
Going to Subscribe to this. I have a 2015 Ranger 27 for sale near me that I am curious about converting to an outboard if I purchase it, the outboards have a higher cruising speed by almost double the inboards.
 
There are a couple YouTube videos on it. Personally, I would wait for a couple years for a good price on a 2018 R27 if price is the issue. Then you Will have all the electronics correct etc. I love outboards as well but that sounds like a big project. Someone will chime in on the hull design. I have to imagine that would be an issue at higher speeds with the old hull design.
I top out at about 38 with 4 people. But....I will admit that is not something I do often or for long periods of time. Even though our hull is designed for it I don’t feel that is a fun time when trying to enjoy the ride. But nice to know you can get out of the way of a storm or make up some time when necessary.
 
Our Volvo-Penta powered 2017 R-27 has a bulge on the bottom for the sump of the diesel engine. It is a significant speed brake. If you were to repower with an outboard, you would probably want to remove the bulge and replace with a faired hull section to give significantly less drag and reduced fuel consumption. Do the older Yanmar-powered versions have the bulge in the bottom of the hull?

Barry Thompson
TOUCAN, R-27 Classic
 
Pretty sure you are dealing with significant hull shape difference between the inboard diesel and outboard models, not just a power swap-out.
 
If you are serious about this I would go to a boat architect/designer and have them give you some advice. If it looks doable I would get the designer to do simulations on the new design. IMHO these are the list of things I would be concerned about:

1. Overall balance and how to mount the outboard. The transom on my RT25SC is quite thin. I assume you may be thinking about mounting the outboard on a bracket. The transom may not be sufficiently strong for a bracket and you need to mount the bracket such that the outboard is at the correct height throughout its power range and boat manuevering.
2. Hull shape - the bulb on the bottom for the diesel engine and the shallow dead rise at the stern. Both could have significant affect on speed and rough water performance.
3. Diesel or gas outboard- if gas, can you use the same fuel tank and how do you clean it. Also for gas you will need a ventilation system that meet Coast Guard requirements.
4. And probably the biggest obstacle, who will you get to insure this modified boat. With the proper paper work from a boat architect/designer it may be possible.

The effort to convert looks significant including the cost. If all you are trying to do is have a boat that is easier to maintain the engine, I think you need a different boat. Also the engine is not the only system that is hard to maintain on these boats.
 
There seems to be a lot of practical issues with doing the conversion, including some not mentioned here. There are some pretty good internet discussions on this issue. My generator uses diesel, i believe the hot water for the heater comes from the diesel, you lose the platform at the back but you gain the area where the inboard is. Another big plus would have been getting rid of some of the engine noise, but perhaps there is another way to deal with this. I think the biggest problem is that i do not use my boat enough and that is not always good for equipment. Seems like things run better when there are used on a regular basis. Thanks for all the comments here!
 
I am left wondering, why not just sell the diesel boat, and buy any of the outboard models?

Cheaper, easier, faster to accomplish, and no chance of making a mess of things.

What am I missing?
 
FWTMD":gex52149 said:
I am left wondering, why not just sell the diesel boat, and buy any of the outboard models?

Cheaper, easier, faster to accomplish, and no chance of making a mess of things.

What am I missing?
Click to expand...

Good question - I do not really want to go fast as I do not like planing over waves and pounding all the time. I just want a reliable motor. Because the Yanmar is virtually inaccessible I cannot work on it and have to pay for everything. I enjoy working on my boat. RIght now it is in the shop for the last month and the bill is going up at a 1,000 a week for what started out as a starter issue which is normally not that big a deal. Biggest thing is i lost use of my boat for some of the best weather up here for the year. The simplistic thinking was to put a 150 HP outboard on it and just run it at the same speed over the water as the Yanmar. I will have 5k in repairs here this month on the Yanmar for presumably minor issues and a new Outboard was 13k or something. I have another outboard that i have run 15 years probably 1500 hours and never had a break down yet. The yanmar only has 350 hours on it. There must be something to this as a lot of the new Ranger Tugs have outboards on them. I would prefer the Yanmar diesel if i did not have these issues.
 
I have been through this type of situation in the past probably like most boat owners and when it's time to sell just do it and move on. Life is short and it is just a boat.
 
Interesting. Clearly it was more than a starter. What more was involved?

Re-powering with another diesel is another option, but probably not a fun thing to consider.

But a full switch to outboard, it seems to me, would involve a lot more than a $15k outboard hanging off the back. You have mount issues, fuel tank issues, you have the diesel to pull out, the shaft to pull, and then plug the shaft cutlass bearing hole, and the helm engine controls as well as engine status screens. And that likely omits a lot of other details. Not to mention you are pulling weight out of the center then adding weight way off the stern, which will have a big impact on trim / balance.
 
ksmoth62":3q1pwwfr said:
I have been through this type of situation in the past probably like most boat owners and when it's time to sell just do it and move on. Life is short and it is just a boat.
Click to expand...

This was good advice and this is what we ended up doing. We got a new R23 and was the best choice we ever could have made - all complaints solved.
 
Matty":3kus8cee said:
There are a couple YouTube videos on it. Personally, I would wait for a couple years for a good price on a 2018 R27 if price is the issue. Then you Will have all the electronics correct etc. I love outboards as well but that sounds like a big project. Someone will chime in on the hull design. I have to imagine that would be an issue at higher speeds with the old hull design.
I top out at about 38 with 4 people. But....I will admit that is not something I do often or for long periods of time. Even though our hull is designed for it I don’t feel that is a fun time when trying to enjoy the ride. But nice to know you can get out of the way of a storm or make up some time when necessary.
Click to expand...
Agree on going full throttle. Not something I do often. But is has definitely help me make a bridge opening a time or two.


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