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  #1  
Old 10-18-2013
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Replacing Inboard with Outboard

You might think I'm nuts but I can't see why it wouldn't work. Maybe I'm missing something. I have a 1970 27' Newport weighing about 6000 lbs with a corresponding 1970 A4 inboard. It starts and runs fine so far but it's getting water into the crankcase and I know there's some serious work ahead, probably a rebuiild. I added electronic ignition this year so it's easier to start but in association with the expected upcoming rebuild and the fact that I have some vibration in the driveline indicating (I think) either bent prop, bent shaft, bearing, etc, I'm wondering if just pulling it and putting on an outboard wouldn't be a better and cheaper answer. We sail on an inland lake and just need propulsion to and from the dock and a little motoring when the wind won't cooperate.

Some pondering on issues:
Positives reasons to change:
1) Easier to pull the motor for repairs
2) Easier to winterize-pull it and take home to the warm garage
3) No propshaft issues (as long as the lower unit is cared for and if there are, see #1)
4) If I use a 4 stroke-use the same fuel tank and simply run the fuel line out the transom
5) If I use an electric start with shifter/throttle controls it would have the same setup as I have now
Possible negatives:
1) Does it change the weight balance of the boat?
2) Is the transom sturdy enough (although this old boat is made like a TANK)
3) Would have to fill in the through hull for the water intake as well as for the propshaft and propshaft mounting bolts).

If this is a foolish idea I know you all will know and know why it is. I appreciate any input from much more experienced boaters than I. Thanks in advance.

PS-I'd take any suggestions on a good long-shaft replacement. The A4 is rated at 30 hp but don't think I'd need that much hp in an outboard. But once again, I defer to the experts.
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Old 10-18-2013
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Re: Replacing Inboard with Outboard

Our boat is also 27ft and displaces close to 8000lbs, she was original designed for an 8hp inboard. The inboard was a block of rust and I didn't want to pay close to 3x what we paid for the boat to put a new inboard in place, so we mounted an outboard off the transom.

We were told you needed 1 hp per ton of displacement, which would mean we needed at least 4 hp. Rather than "risk" it, we went with the Tohatsu 6 HP Sail Pro, which has an extra long (25in) shaft and a small alternator, we bought it new for roughly $1500. The motor performs wonderfully and pushes our boat at about 5.5-6 knots at 20% power, which is better than the original inboard would do. With current and wind, that obviously changes, but I've never seen it make a major impact. You do NOT need anything over 6 HP, I've seen 15hp outboards on the back of 23ft sailboats before and it is way overkill. With the outboard, you are looking to make and keep momentum, it isn't going to push the boat beyond hull speed.

The biggest drawback is the prop coming out of the water with any kind of wave action, resulting in a loss of thrust. It has not been an issue for us yet, but it can make getting in and out of places with a lot of big waves complicated. This is the biggest concern, but is manageable if you learn to compensate by sailing the boat. The 25in shaft definitely helps, but it's not perfect. We've pushed against 20 knot headwinds with small swells fine, but you aren't gonna have the same performance you will with an inboard and you can expect to have issues with this at some point.

You will want a good outboard mount with plenty of travel, don't cheap out here, we did and I regret it (we are replacing it next week). I looked around and at the recommendation of James Baldwin of AtomVoyages, we went with the Garhauer OB-125 mount ($250, roughly). The mount is spring loaded to help with weight and has close to 15in of travel. I should be able to comment on it's performance in a week or two, after I pull the old one, fill the holes, and put the new one on.

As for your negatives:

1. We didn't notice any significant balance changes. The motor weighs 75lbs, which should not have a huge impact, but it might. You can always add weight up front to compensate.

2. Ours is over 1/2'' thick and we reinforced it with a 1in backing plate to be safe. There will be a lot of pressure on the transom at this point, so reinforcing it as much as possible is definitely recommended.

3. We filled the stern tube with epoxy and glassed over it, if you really want to get fancy, you can build a wood filler for the rudder and keel that removes the empty space where the prop normally sits. We haven't done this yet, but James Baldwin has some info on his site about doing this. We also removed the thru hull and seacock for the motor.

As for using your existing fuel tank, I'm not sure I would do that. If you are going to pull the A4, you might as well remove the risks of having gas in the cabin all together and find a convenient way to mount the fuel tank outside. We removed everything and it opened up a lot of storage space, also removing odors associated with inboards completely.

Last edited by Shinook; 10-18-2013 at 05:56 PM.
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  #3  
Old 10-18-2013
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Re: Replacing Inboard with Outboard

Shinook,
Thanks for the EXCELLENT answer. I was hoping someone with experience doing it would reply and your information was just what I was looking for. I thought it could be done but I find a lot of things look good in my head and not always in real life!

I wonder if I might ask: Does your motor have electric start, remote control for throttle and shift? Since my tiller is forward in the cockpit, it's a bit hard to "lean over the transom" to do those functions as some smaller boats can do.

Thanks again for the encouragement and information.
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Re: Replacing Inboard with Outboard

No electric start, I don't think that's an option for the Tohatsu models, I could be mistaken, but I know ours doesn't have it. Ours starts pretty easily though, we also pull it out of the water when we are sailing or leaving the boat at the slip, so going back there is required anyway. It isn't that hard to pull up and down if you have the right mount.

There is a remote control kit, but that would get messy, you have to run a series of cables back to the motor. I took one look at it and said forget it.

When we use the motor, I rarely do much with the power settings. I usually set it and leave it where it is, then return to the cockpit for however long we plan on motoring. The only exception is docking, when we do that I sit on the aft lazarette lid and can easily reach the controls from there, of both the tiller and motor.

I won't lie, it's not as convenient as an inboard, but you learn to deal and it's certainly better than what it costs to put an inboard in. I don't regret our decision, I'd do it again.
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Re: Replacing Inboard with Outboard

Thanks again. Very good info and much appreciated.
Happy sailing! We got a few flurries of snow but supposed to warm up tomorrow and Sunday so, sadly, after that we'll winterize the A4 and call it a season.
Best to you.
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Re: Replacing Inboard with Outboard

Quote:
Originally Posted by Lubrdink View Post
Shinook,
Thanks for the EXCELLENT answer. I was hoping someone with experience doing it would reply and your information was just what I was looking for. I thought it could be done but I find a lot of things look good in my head and not always in real life!

I wonder if I might ask: Does your motor have electric start, remote control for throttle and shift? Since my tiller is forward in the cockpit, it's a bit hard to "lean over the transom" to do those functions as some smaller boats can do.

Thanks again for the encouragement and information.
Modern outboards are very very good.I have a 9.9 merc big foot high thrust electric extra long shaft that has an unbelievable amount of power for a 9.9. It pushes a 40 foot defever trawler just fine so would certainly give you tons of reserve power when needed as well as using very little fuel.

FourStroke 8 - 9.9 HP | Mercury Marine
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Re: Replacing Inboard with Outboard

Thanks BFloyd. More good info for my decision. I appreciate you taking the time.
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Re: Replacing Inboard with Outboard

Quote:
Originally Posted by Lubrdink View Post
Thanks BFloyd. More good info for my decision. I appreciate you taking the time.
your welcome. As a matter of fact I got the merc by accident. I ordered a custom built boat from Wooldridge boats two years ago and they installed this bigfoot for a kicker. Well the 9.9 isn't needed with my merc 115hp smart craft 4 stroke main engine because the computer controls on the big engine allow me to troll slower and more economically with the 115. So I tried the 9.9 on the trawler to see how it would do cause I had noticed on my Wooldridge how incrediblely powerful the little 9.9 was so thought it would work on the defever. It has the extra long shaft which would make it great for a sailboat and a bigger stronger mount plus electric start and trim. Nice little motor for boats in need of dependable power that sips fuel.
good luck
best wishes
britt
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Re: Replacing Inboard with Outboard

Why not fix your A4? The A4 is simple enough that anyone can do a complete rebuild if needed (and it likely isn't).

I've had outboards on sailboats and I hate them. They don't perform as well and they look like ass.
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Re: Replacing Inboard with Outboard

You don't need over 10hp, so an electric motor is an alternative. Golf cart technology, and conversions forums are good.
Raise the boats value instead of lowering it.
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