What to do about missing inboard motor?

[Shaun R.]

Recently acquired a 1981 Sovereign 7.0. The boat had the option inboard motor, but as you can see in the picture there is no motor there. The boat also has an outboard mount and I plan on outfitting it with an outboard 4 H.P. motor. I plan on sailing in the lakes of Idaho and as of now, not planning on installing an inboard motor. What concerns should I have with an 18" x 13" hole by my transom?

I was thinking either placing a box over the hole or mounting a cooler down inside. Is this hole sound for sailing? Will my aft end just sink into the lake? The three holes towards the transom, guessing those were for fuel, power, and cooling? Should I plug those? Forgive me, lots of questions.

 

[MikeHoncho]

I’m confused by the picture. Could you post more and maybe some back a bit for orientation?

 

[Shaun R.]

Sorry, I took a screenshot of a video I made. I'll post a shorten version of the video focusing just on this hole.

 

[Shaun R.]

Inboard Motor Hole

Uploading to share on forums.

rumble.com

 

[kloudie1]

Stuff to review:

Sovereign Yachts

Information about the Sovereign brand of sailboats

sovereignyachtcorp.com

Little Gypsy: August 2016 (svlittlegypsy.blogspot.com)

 

[PaulK]

The photo looks like it is a setup for an inboard-mounted outboard. You clamp the outboard to the forward edge of the box and let it stick down through the hole into the water. The holes at the aft end are for fuel lines, battery cables and possibly cooling water exit. This arrangement keeps the prop in the water much better than having the outboard mounted on the transom. The cutouts on the sides of the box may allow the motor to turn, increasing maneuverability, though it makes things a touch more complicated. The recent Flying Tiger 10 has a similar outboard - through-the-bottom setup.

The hole in the aft section of the hull (not in the transom) does slow the boat down when sailing. So does having the engine's lower end dragging in the water all the time. People often remove the engine and put it in the cabin once they're sailing and sometimes there are doors or plugs that cover the hole to improve hydrodynamics. If you like fishing you could put a screen across the bottom and use it as a live-bait well. But you'd have to figure out where else to mount the motor.

 

[jssailem]

@PaulK identified the design and function of the hole in your boat.

What you do with it is pretty much about how you plan to use the boat and what conditions in which you plan to sail.

Boats with such designed outboard in the hull often are used under power. I have seen many boats on the Chesapeake, used for fishing, that have this design. With all the engine controls inside the boat, the use and service of the motor is easier, than hanging out over the transom to do such work. I had a transom motor on my trailer boat. It worked to move the boat in and out of the launch ramp. I would take the 60lb motor off the transom and store it in the cabin, when I was out sailing. It just reduced my sailing pleasure.

That said there are draw backs for a sailboat. The hole will catch that swell or chop you just ran over and water will slop up into the hole and perhaps the cockpit. You can fashion a plug to help keep the water out of the cockpit. Perhaps a cooler can serve as your plug. Your creativity is being challenged.

The hole will be a source of hull drag when sailing. From a design perspective, you do not see racing boats with holes in their hull. It is perfectly all right to accept it and move on to play on the water. You could say, I do not want a hole in my boat. Then you would flip the boat over and put on a fiberglass patch, resolving the issue.

You could also go electric and use the hole for your battery/electric motor mount.

So many options. It is your boat and you get to create it as you envision.

 

[rgranger]

You could put one of these over the hole

Just kidding of course...

 

[Ralph Johnstone]

You could put one of these over the hole

That's never going to work. You know some fools going to come along and lift the lid and then it's all over except for the last few bubbles marking where the boat went down.

You need a lid locker:

Always safety first.

 

[rgranger]

That's never going to work. You know some fools going to come along and lift the lid and then it's all over except for the last few bubbles marking where the boat went down.

You need a lid locker:

View attachment 207685



Always safety first.

View attachment 207686

My stomach hurts

 

[Shaun R.]

You could put one of these over the hole

View attachment 207677

Just kidding of course...

That was actually my first thought... lol

 

[Shaun R.]

The photo looks like it is a setup for an inboard-mounted outboard. You clamp the outboard to the forward edge of the box and let it stick down through the hole into the water. The holes at the aft end are for fuel lines, battery cables and possibly cooling water exit. This arrangement keeps the prop in the water much better than having the outboard mounted on the transom. The cutouts on the sides of the box may allow the motor to turn, increasing maneuverability, though it makes things a touch more complicated. The recent Flying Tiger 10 has a similar outboard - through-the-bottom setup.

The hole in the aft section of the hull (not in the transom) does slow the boat down when sailing. So does having the engine's lower end dragging in the water all the time. People often remove the engine and put it in the cabin once they're sailing and sometimes there are doors or plugs that cover the hole to improve hydrodynamics. If you like fishing you could put a screen across the bottom and use it as a live-bait well. But you'd have to figure out where else to mount the motor.

Thank you for the information. I read on Wikipedia Sovereign 7.0 - Wikipedia that it was offered as an option with an inboard diesel motor. I like the idea about moving the outboard - inboard. I want to sail, not burn fuel so using a small motor to get me away from the docks is all I want.

 

[Shaun R.]

@PaulK identified the design and function of the hole in your boat.

What you do with it is pretty much about how you plan to use the boat and what conditions in which you plan to sail.

Boats with such designed outboard in the hull often are used under power. I have seen many boats on the Chesapeake, used for fishing, that have this design. With all the engine controls inside the boat, the use and service of the motor is easier, than hanging out over the transom to do such work. I had a transom motor on my trailer boat. It worked to move the boat in and out of the launch ramp. I would take the 60lb motor off the transom and store it in the cabin, when I was out sailing. It just reduced my sailing pleasure.

That said there are draw backs for a sailboat. The hole will catch that swell or chop you just ran over and water will slop up into the hole and perhaps the cockpit. You can fashion a plug to help keep the water out of the cockpit. Perhaps a cooler can serve as your plug. Your creativity is being challenged.

The hole will be a source of hull drag when sailing. From a design perspective, you do not see racing boats with holes in their hull. It is perfectly all right to accept it and move on to play on the water. You could say, I do not want a hole in my boat. Then you would flip the boat over and put on a fiberglass patch, resolving the issue.

You could also go electric and use the hole for your battery/electric motor mount.

So many options. It is your boat and you get to create it as you envision.

I will definitely try and plug this spot with a cooler to start. I work with a crew of plastic fabricators, so I have ideas. I am considering patching it with fiberglass, but I want to get it out on the water a couple of times to see if the drag bothers me or not.

Really appreciate the inputs from everyone.

 

[MikeHoncho]

Don’t be fooled by the idea that that a gas outboard burns less fuel than a diesel. But if all you want is mobility to and from a dock then a small outboard on a transom mount is the cheapest. My Yanmar 2gm20f rated at 18hp is currently burning .44 gallons a hour pushing a 10,000 30ft Hunter at 6 knots.

 

[Ralph Johnstone]

My Yanmar 2gm20f rated at 18hp is currently burning .44 gallons a hour pushing a 10,000 30ft Hunter at 6 knots.

Hi Mike, what RPM are you pushing for 6 kts ? I figure my fuel consumption at 2800 RPM and 5 .5 kts is close to 1 l/hr. which is 0.264 USG/hr. And it's certainly not due to clean living on my part.

 

[garymalmgren]

Atom has been very serious about well mounted outboards.
Maybe a little over the top for your needs but worth checking out.

The Improved Outboard Well – Atom Voyages

 

[shemandr]

The Hobie 33 had an outboard motor well - with a hole thru the hull which the shaft of the motor would protrude. The intention of the design was to pull the motor up and slide the shaft into the compartment for sailing. There was a plug for the hole in the hull. Surprisingly not very much water would come in because that part of the hull is barely, if at all, underwater. In my opinion, it was a PITA to do but you couldn't argue with the sailing performance.
When sailing outboard driven sailboats, (C&C 25, Ranger 23, Mark 25) in races that counted to us we would take the motor off the transom and put it on a tray in the cabin. That was a PITA too. And as backs got older we took the engine off less.
But I'd encourage the OP to take a look at the Hobie 33 design to see what can be learned from it.

 

[MikeHoncho]

Hi Mike, what RPM are you pushing for 6 kts ? I figure my fuel consumption at 2800 RPM and 5 .5 kts is close to 1 l/hr. which is 0.264 USG/hr. And it's certainly not due to clean living on my part.

I hit a log that threw my variable pitch prop out of balance so I have been motoring at 2800 and that is what the calculations are on. I normally motor at 3000-3200 and at 6.0-6.5. I’ve been pretty heavy on this trip with provisions and water for two weeks . This calculation includes motor sailing. Tacoma to Nanamio hitting all the stops on the way back. Just crossed the strait.

 

[MikeHoncho]

Hi Mike, what RPM are you pushing for 6 kts ? I figure my fuel consumption at 2800 RPM and 5 .5 kts is close to 1 l/hr. which is 0.264 USG/hr. And it's certainly not due to clean living on my part.

Outboard?

 

[Ralph Johnstone]

Outboard?

I think it's an inboard. Nothing hangs over the back end that I can see..

I've got to do my callcs again as either my tape measure is short or someone is adding small amounts of diesel fuel every day just to drive me nuts.