Installing an OutBoard Well in a N28

[Phillip of ninoxyacht]

My N28 is 50 years old now, and the diesel motor died about 3 years ago.

I have had mixed success with outboards - they are easy to install on a bracket, and provide just as much horsepower at a fraction of the price, yet out the back is difficult to access the controls, to clear weed or to drain the float bowl, etc, and I have had the propeller come out of the water twice, in short, steep waves.

I have been interested in moving the outboard inboard, as seen on James Baldwin's site of Atom and specifically his outboard wells: http://atomvoyages.com/articles/improvement-projects/257-tritonsalty-1.html and he has at least 2 videos of how they were done.

So after 3 years of thinking, I put my long-shaft outboard in my lazarette to see what it looked like:

Day one at the slip yard was polishing one half of the hull, and thinking and measuring the OB and well situation. (engineering). Inside the lazarette, the OB leg looked quite OK too.

Today was the second workday. In about 6 hours I cut the lazarette top much bigger and sanded it smooth. I measured and cut the hull for the OB leg, and sanded the sides smooth. I cut more from the cockpit area in front of where the OB motor will go, to access the controls and to lower the motor. And I cut plywood to make the sides of the OB well. Perhaps the well should be wider, and the cut-out for the leg wider, so that the motor can be swung left and right a little. Maybe I will do that the next day. The pictures tell the story adequately.

I have also sanded (with the angle grinder and flapper discs) the insides of the well, where the epoxy will go, unless I widen the well.

Once the well sides and well forward bulkhead are glued and strong, I will test the height of the motor with a board (like on an OB bracket) and I will test how well the motor can lift its leg. I don't want the leg poking out too far out the back, because I want to mount a windvane there and ladder also.

To be continued.

[Phillip of ninoxyacht]

The photo captions didn't come up. Starting from the second photo they are:  

 1. Cutting the lazarette bigger.

2. Marking out the cut at 30 and 40 cm by 11 cm wide.

3. Approximate sized cuts, needing sanding and finishing. 

4. Need to widen the hole and cut away the front, to lower the motor more.

5. Need also to lengthen the lower hole, to 40 cm long, to make the OB leg vertical

6. Fitting the sides of the well. It is probably too tall; also too narrow to allow the motor to swing.

7. No swinging motor yet, but the height is about right.

8. Almost the right height for the leg too. Can lower it 10cm to match the real water line. Old propeller shaft remains before the rudder (for now).

9. Overall perspective for OB well at a good height.  

 

[Maeling]

Brave work!!  Looks good esp the second photo with the prop deeper.  I remember Evinrude put out a super longshaft Yachtwin 3hp.  Transom mounted the prop would fly out of the water on every big wave.  I like deep. I wouldn't cut the hull further to enable steering the motor but without propwash over the rudder steering will be sluggish at low speeds but you'll find a sweet spot and cope with it.

Good job and a great article - Also nice to see the underwater profile of an N28

Geoff Raebel

[Maeling]

Can you lift the engine out without taking the prop off first.  Not sure I would leave the outboard permanently immersed, even with anodes.  Something like 80% of outboards are used in freshwater - American lakes and rivers. It's only a geographical accident that most of our motors have to run in saltwater and the motors are made from a brew of recovered metal for diecasting.

Geoff Raebel

On Saturday, March 31, 2018 at 8:30:13 PM UTC+11, Phillip of ninoxyacht wrote:

[Calavera]

Thank You Phillip for posting this thread, with great photos too!.

I am only at the 1 year "thinking" point, for a conversion like that, on a Top Hat 25. The TH25 would be slightly easier as the OB well is basically there, with just a cut up the transom to tilt it, & minor work needed to allow the OB to swing, aiding manoeuvring in close qtrs. greatly. If you could get the OB to swing I think it is worth the extra work. .

Are you going to add the little sliding screens around the leg to help prevent following waves from washing in?

cheers

[Phillip of ninoxyacht]

Here are today's photos. Not a lot to see really. Attached is a profile shot for Geoff, of my N28. Unfortunately I can't do it perpendicularly because of the neighbouring boats. And a photo of the rudder and prop shaft area.

I cut a dowel to about 1 inch length, and then I pushed the propeller shaft inwards a few inches. I cleaned the hole (grease) with a cloth and metho and it seemed clean. I sanded with my favourite tool, the angle grinder and flapper disc, the propeller shaft exit until I got bare fibreglass and the bearing material, and I applied the angle grinder on the rudder area as well. Over the prop shaft exit area I applied f/glass tape in a star pattern (vertically, horizontally, diagonally) to secure it and waterproof the area. The rudder had timber under the fibreglass, and I cut 3 plywood panels to get to 36 or 40mm thickness. The panels were hand sawn and then shaped with the angle grinder and epoxied together. I then wrapped a plastic bag around some battens and over the infilling panels, and clamped them in place.

I also began to fillet epoxy the panels of the OB well. Firstly I cut the OBW panels to half the height of the other day, so they will be only about 30cm (maximum) above the slot, and then I chamfered them and began the filleting process. It's always a messy job for me, doing epoxy work and having the stuff run everywhere. The OBW panels are 36cm wide, so I will have space to rotate the OB by about 30 degrees each side, i.e. 60 degrees rotation. That will give the motor capacity to rotate, because there is no prop wash over the rudder, helping steering.

Next time on the boat I will fillet the rest of the OBW panels, and epoxy in place a forward panel to contain water/waves, and a thicker panel to which the OB will be mounted. I have to determine how far forward/aft it will be, and how high it will be (for tilting). When I know that, I will be able to cut inside the slot, to allow the motor to rotate the 30 degrees left and 30 degrees right, and I will cut a slot in the transom so that I can pull out the motor with the propeller. I'd rather do that at the transom rather than lower down near the water line. The hull will not be cut further than the present 40cm because it interferes with tilting in the cockpit area.

The OB will not be permanently immersed. It will rest in the tilted up position, and will poke out the transom. And yes, Calavera, I will probably add the sliding screens around the leg to prevent following waves from washing in. It is a work in process, and I will think of that part once I have the OB mount sorted (i.e. how fore/aft, how high/low, how it tilts out the back).

To be continued next weekend.

[Phillip of ninoxyacht]

A few hours earlier in the week and today, I have epoxied the sides and front of the outboard well. I also epoxied and faired the rudder section and brushed runny epoxy over the shaft plug, to seal it really well.

 

Today I fit the motor in the well, and needed a new bulkhead about 3 inches in front of the other one, with enough room to tighten the screws/bolts to the OB timber pad. I also added backing pads for the windvane, measured for a ladder, polished the hull sides, then sanded the bottom of the boat, and gave it its first application of primer.  

The well is not perfect. It is not perfectly vertical and the epoxy is messy. But it is progressing. The tilt mechanism is still a thought in process, but I played around with the OB and saw the dimensions today. The wind vane will go ahead regardless of the tilting mechanism of the OB well. Otherwise I'd take forever in the slip yard, getting everything perfect.

[Phillip of ninoxyacht]

A few compromises are being made  to economise time and because of the dimensions of the well/lazarette and the length of the long-shaft motor.

Firstly, the length of the OB leg extends too far out the back, and I didn't want to extend the arms and legs of the windvane, as well as move my mainsheet traveller forward, because of the tilting of the OB motor leg and head, respectively.  So instead of extending these things, I will use the OB well as a well for a while to see how it goes.

If I like the above scenario with the leg and propeller poking out only about 10cm or so, then it is easier engineering, and the head of the OB looks like this:

And it's only 27kg. So it could be stored inside the yacht, or I build a box around it.

Here I have cut out a section for the propeller, as Geoff suggested. It is 23cm wide by about 6cm fore-aft, to suit my high-thrust propeller:

I also put on some brackets for the windvane.

And this is the well:

with the forward bulkhead and the extra bulkhead which takes the weight of the OB and the space between them is to tighten the bolt/screw things. It also gives room to tilt the motor. There is some room to swivel the motor left and right; there'd be more room if I lower the sides of the well by an inch, because I made it too narrow.

The next jobs are to antifoul the boat, to get the legs of the WV welded, and to epoxy the new cuts in the transom for the propeller and the new bulkhead.

If I don't like lifting the motor, then I can later (a few months time) extend the WV arms and legs, and move the mainsheet track to allow the OB head to tilt. But overall, I think the well installation brings the propeller about 70cm forward, (compared to an OB bracket) and that will mean less pitching and less times it will come out of the water on steep chop, as experienced in the past year.

[Phillip of ninoxyacht]

The yacht has been launched and I sailed the 20nm home.

Here are some statistics in the photo:

 The 63cm is from the painted antifoul line to the bottom of the OB motor, and 55cm is the real water line to the bottom of the OB motor. So the propeller is quite deep in the water.

36cm is the length and breadth of the OB Well, more or less. It is all the room I had in this yacht.

40cm is the present distance between the corner of the transom/hull to the shaft of the wind vane. It needs to be extended by another 10 or 12cm to enable the OB leg to click into the horizontal position, to eliminate drag, as per the next photo:

In my 20nm sail back to the mooring, I put the petrol tank above the motor well, and tied it down from moving. This stopped me from lifting the motor up (vertically) to eliminate drag. I think the better idea is to extend the wind vane another 10cm aft, so that the OB motor's leg can be locked into the horizontal position, and that will eliminate it's drag. And it means I will not have to lift the motor vertically. The drag on the leg (in the vertical but lowered vertical position) was too much, and it will be better to be able to pivot or lift the leg until it locks into a horizontal position clear of the water.

That will mean cutting the OB slot in the transom another 5cm higher, or so, and then moving the mainsheet traveller, probably. It will mean then that I will have to make new arms and legs for the windvane, to extend the WV the 10 or 12cm more aft. It is the better solution to eliminate drag, and still a good solution for the WV. All this can be done with the yacht in the water, and not at a slip yard.

The OB motor in the well was much easier to pull start, to stop, to change gear and throttle, than it was when it was out the back of the transom on an OB bracket. Also in the well, it will be much, much easier to clear the propeller of weed or to drain the float bowl or any other maintenance.

The WV extending and lifting the OB leg, will be done in the next few weeks. I hope you have learned something useful from my post, as much as I have learned from doing it.

[C30 Stargazer]

Hello. I've been reading your posts with interest. BTW, there is a yacht with an OB in a well that's been added I think, on the Central Coast near Woy Woy. I passed it in the Woy Woy channel a few weeks ago...

I think what you've done looks very usable. Personally I'd argue that you should seal the well from the rest of the boat - either with a bulkhead across the inside of the hull forward of the new well or seal the sides and front - whichever way, to stop water ingress from a following sea. In 35 knots or so on the weekend in Sydney harbour, the waves piled up behind my boat and flooded the cockpit via the cockpit drains in an impressive manner. Of course they weren't that high but at sea.....

I had a catamaran with a long shaft in a well and the well occasionally filled with water. Never drowned the engine but it was surprising what would surge up from underneath...

Bravo to you for your solution!

Bruce