Engine well 101

I'm looking for information on constructing an engine well. I tried searching here but found very little. Is there any literature on this subject?
Thanks.

 

Meaning what ? A well inside a boat an outboard engine fits into ? You need to give some detail

 

+1 re Mr E's request for more details please.
What type / material / / power / size of boat will you be constructing the well in?

 

Sorry yes a 28' trimaran 3500lbs. I believe the original plan used the lazarette aft the cockpit. Im not sure what size engine but guessing a long shaft 9.9?
The boat has a deck that goes across the hulls so a sled may not be possible?
I found Atom's website that shows the outboard tilting up through the transom I'd like to use a transom hung rudder so I guess it needs to slide up. Ideally all the way out and then plug the hole.
Thanks.

 

Might you not save yourself a lot of work by just bolting one of these a little off centre on the transom? Cutting a hole for a well isn't too hard,nor is building a few panels to line it.It is however quite hard to create a well that doesn't add a fair bit of drag-unless you slot in a plug conforming to the original hull shape when the motor is stowed.

 

Wet feet I don't think I can squeeze the outboard and the rudder on the transom. Definitely would want to use a plug to reduce turbulence.
The other option wind be a spade rudder and mount the engine as you suggested but only if this option isn't workable. Thanks for the input.

 

If this is to be used other than on small lakes, you need a fairly well engineered and though-out well. Twenty eight feet will need the OB in a well forward of the transom in order not to lift the prop in a seaway. The power head needs to be slammed all the way down to the waterline. There are aftermarket extra-long shaft conversions that are worth the price. They come with a new shaft, new shift link, and about a 5 inch spacer.

Since the power head is slammed down, it can't tilt clear into the hull with the normal pivot. Depending on space you either need to build a pivoting plate for the bracket to mount to, or use a jack plate mount.

The motor doesn't have to tilt straight back. If you have a transom hung rudder, you can build the mounting plate at a 30 degree angle and have the motor kick up to the side of the rudder. This lets you kick the prop up outside the transom in a slot to the side of the rudder, and it saves you a couple feet of precious space. And it's arguably the simplest of installations and has the smallest volume wet well. My Cal 28 monohull had a Mercury 15 extralong shaft with the bottom of the engine cowl 1 inch above the waterline in the well, and it lasted twenty years in tropical salt water. I pulled it once a year for 2 hours of maintenance and put it back.

It's surprising how quiet the water is at the well, even when anchored in storms. I briefly owned, but long knew, a 36 footer that had an outboard well in the middle of the aft cabin. The well lip was three inches above the waterline when sleeping in the aft cabin, and it housed a 40 hp outboard, so the hole was about 2 feet square. There was no isolation - it flooded the entire hull if that lip went under. This thing went though countless hurricanes in the Florida Keys and never sunk in all the years I was there. Not that I recommend such a setup, but they work better than they ought to.

With fourstrokes, check the crankcase and fuel system integrity when tilted way up. This and the turning angle is what usually constrains the geometry of these sort of wells. They have to be designed around a particular engine if you want a space efficient design. You don't want gas pouring out of the carbs into the engine or into the boat. Most have an "up" side for laying the motor on it's side. That has to be respected when kicked up.

 

I hadn't considered angling the engine mount to clear the rudder .. so once tilted can the area below the waterline be plugged?
Is sliding the engine up out of the well not a good option?
Is the 9.9 the right size? I see there's also a 6hp tohatsu with a big prop. It weighs about 40 lbs less.

 

It probably depends on the charging system you want. The bigger ones have a useful charging system for house loads.

Sliding it up tends to interfere with stuff, but it depends on how much volume you have in the back. And the 9.9's weigh north of 100 pounds now. That takes a tackle to lift, or a hefty spring-loaded transom bracket. And when you actually go through the design process, lifting doesn't seem to have much of an advantage over tilting vis a vis space savings. Routing the electrical and fuel lines can be a bit of a challenge.

 

Why would a sled not be possible? Hang it under the deck with the engine projecting behind it, it's the simplest option. If you make the sled arm out of a pipe you can use that as your gas tank.

 

Rumars the back of the boat is decked across the hulls so I don't think I could go the sled route. I'm thinking the simplest approach is a vertical slide? Seems it would have the smallest hole and could be plugged while sailing. Since this would be in the lazarette if I used the 6 hp would pulling it all the way out and hanging it on the pulpit be possible? I can (currently) manage 60 lbs. Thank you for the input!

 

The sled projects behind the deck and puts the motor after the deck edge between the hulls. All you need are two brackets under the deck, a shaped arm to take the outboard, and a lifting arrangement. Illustrated here by the guy who popularized the arrangement.

 

I see that looks doable for sure. No hole in the boat either. Any idea where to find details on the design of the sled? Thank you.

 

John Marples still sells plans for Searunners, contact him and ask how much for the sled plans only. Searunner Multihulls - Home https://www.searunner.com/index.php

 

Thank you Rumars. Mr. Marples provided the details free of charge. What a classy guy.