Considering outboard converson for my 23' Seabird
#1

I have a 1969 Seabird, and am considering upgrading to an outboard. The boat itself is in, for the most part, very good condition. Transom has been rebuilt, hull core is dry, Cockpit floor looks so so, however the layout works very well for me. The primary problems are 1.4 mpg, 65 gallon fuel tank, and the wet bilge causing more engine maintenance that ideal. Current engine is a Mercuiser 2006 350 Mag MPI Horizon which runs well.
Going to an outboard would save about 400 lbs., inc. the bracket weight. I would use the 300 Merc. SeaPro. I am slightly conerned as to whether the stability will be the same, as this 24 degree hull rocks badly at low speeds. This cockpit does drain to the bilge, which is a bummer, but raising it up 6" would cause stability problems.
Currently run at 3,300 rpm to 3,600 and only see about 20 knots. The prop is correct, as the previous prop had a more pitch and I warped some exhaust valves. Boat is pretty heavy, but I have not had it weighed. I am happy to run at 20 knots, as most of the time that is all the conditions permit where I am, 60 miles north of San Francisco. A friend has an Osprey 24 with Vovlo DP, he gets 1.8 mpg. So I think my 1.4 figure is reasonable. I need to some some fairing on the hull, as a layer of epoxy barrier coat went on too rough. I have considered upgrading to a Steiger Craft 23' or an Osprey 24, but my layout is better than either of these boats.
So the big question is what could I expect in fuel consumption? I would use the Merc. 300 hp SeaPro on a bracket. Upgrading would give me more range, less maintenance, more cockpit space and better safety.
Going to an outboard would save about 400 lbs., inc. the bracket weight. I would use the 300 Merc. SeaPro. I am slightly conerned as to whether the stability will be the same, as this 24 degree hull rocks badly at low speeds. This cockpit does drain to the bilge, which is a bummer, but raising it up 6" would cause stability problems.
Currently run at 3,300 rpm to 3,600 and only see about 20 knots. The prop is correct, as the previous prop had a more pitch and I warped some exhaust valves. Boat is pretty heavy, but I have not had it weighed. I am happy to run at 20 knots, as most of the time that is all the conditions permit where I am, 60 miles north of San Francisco. A friend has an Osprey 24 with Vovlo DP, he gets 1.8 mpg. So I think my 1.4 figure is reasonable. I need to some some fairing on the hull, as a layer of epoxy barrier coat went on too rough. I have considered upgrading to a Steiger Craft 23' or an Osprey 24, but my layout is better than either of these boats.
So the big question is what could I expect in fuel consumption? I would use the Merc. 300 hp SeaPro on a bracket. Upgrading would give me more range, less maintenance, more cockpit space and better safety.

Last edited by c1steve; 11-13-2020 at 04:48 PM.
Likes:
#2
Senior Member

Don't you think pulling a V8 and outdrive from low in the bilge and installing it higher and aft of the transom cause more stability issues? If it is a concern already, you are probably best to dump it and set up another boat the way you want it.
It sounds like this boat has a fairly good deadrise to the hull. Better cutting through rougher water but they do require a higher rpm (and more fuel) to plane. Also, will have more rock to them. Something else to consider.
It sounds like this boat has a fairly good deadrise to the hull. Better cutting through rougher water but they do require a higher rpm (and more fuel) to plane. Also, will have more rock to them. Something else to consider.
#3

Before I started anything too drastic with that hull, I would check out the stringers and the transom for any water intrusion. I think that might be a balsa-cored hull also, so there could be water-logging going on there also.
#4
Admirals Club 


That’s a nice looking boat .
I don’t know much about converting it to outboard with bracket,, but I think since you already feel it’s unstable with the low center of gravity with the inboard, you will just make it worse with the conversion. Raising it .?
You could however ,,,, convert it with a bracket, add as big a plane trim tab as possible , use the space where the engine sits for a new sea keeper, and boom!
You’re broke!
BS I like that boat
I don’t know much about converting it to outboard with bracket,, but I think since you already feel it’s unstable with the low center of gravity with the inboard, you will just make it worse with the conversion. Raising it .?
You could however ,,,, convert it with a bracket, add as big a plane trim tab as possible , use the space where the engine sits for a new sea keeper, and boom!
You’re broke!
BS I like that boat
#5
Senior Member

That’s a nice looking boat .
I don’t know much about converting it to outboard with bracket,, but I think since you already feel it’s unstable with the low center of gravity with the inboard, you will just make it worse with the conversion. Raising it .?
You could however ,,,, convert it with a bracket, add as big a plane trim tab as possible , use the space where the engine sits for a new sea keeper, and boom!
You’re broke!
BS I like that boat
I don’t know much about converting it to outboard with bracket,, but I think since you already feel it’s unstable with the low center of gravity with the inboard, you will just make it worse with the conversion. Raising it .?
You could however ,,,, convert it with a bracket, add as big a plane trim tab as possible , use the space where the engine sits for a new sea keeper, and boom!
You’re broke!
BS I like that boat

#8

When I bought the boat 20 years ago I had the transom rebuilt. The stringers/engine beds are good and the balsa cored hull appears to still be in good shape. There was a small amount of wet core at the toilet thru hulls, but I fixed that in the beginning. It is a 24 degree hull, that is an issue. If I knew of a similar boat that did the IO to outboard conversion and things were satisfactory, that would be helpful.
Brisboats is probably correct, the cons outweigh the pros significantly. I have been looking at a new Steiger 23 DV. Nice boat, but for that money I could buy a very nice larger boat.
Brisboats is probably correct, the cons outweigh the pros significantly. I have been looking at a new Steiger 23 DV. Nice boat, but for that money I could buy a very nice larger boat.