A25: Emergency Propulsion/Kicker Motor

[Cappuccino]

Hello to all and happy holidays!
Just like the topic says I am about to convert my 1972 A25 displacement hull trawler from a single diesel trawler to dual power; diesel + outboard trawler. My A25 currently has a Vetus M4.14 32hp diesel with about 400hrs in excellent condition. My plan is to add an 25hp four stroke outboard (143lbs) to the transom of the boat for both emergency and kicker use. The plan also includes adding the controls of the outboard to the helm; electric starter, throttle/gear level, rpms, etc. I also intend to modify the linkage of the rudder and have the outboard also steer with the steering wheel. My A25 currently has a 3ft long custom made fiberglass swimming platform which will be modified in order to adapt the new outboard motor. The plan is to make a hole in the swimming platform in order to pass the new outboard shaft thru it. The outboard motor will be in the centerline, not to one side. I am going to extend the platform about 8 inches more (3'-8") and also extend the hull lenght to the new swimming platform's new length. The hole that is going to be made into the swimming platform for the shaft of the outboard to go thru is going to be sealed so that the swimming platform provides extra buoyancy. The aft section of the swimming platform, which in this case would be the end of the hull will be flattened hence converting the displacement hull to semi-displacement, or at least that is my intention. And finally the cowling of the outboard is going to be covered with a custom fiberglass stair cover. The idea is that when the boat is out for the water you will only see the propeller and lower unit of the outboard hanging beneath the swimming platform. And when the boat is in the water you'll only see a nice swimming platform with a nice fiberglass stair complete with teak steps and all.
So, after all this is done I should end up with a 27'sh lenght waterline (added speed), a semi-displacement hull (flattened transom), added buoyancy in the aft, with about 57hp in combined power and best of all an emergency power option for when the diesel decides to quit or the propeller decides to catch some debris or ropes floating in the water.
I have some questions or doubts that are still floating in my mind...
1) Will I be able to hit say 10 to 12 knots with this setup?
2) Will the extra 25hp of the outboard plus the 33hp of the diesel be enough to get to 10 to 12 knots?
3) I know that true planning will be impossible or near impossible with that extra horsepower but maybe plane a bit?
4) Will the turbulence of the diesel prop affect too much the prop of the outboard even though they will be both deep enough with no air? And if so, could I reduce the rpms of the diesel enough to make the boat go to a certain speed and use the outboard as a kicker/main power and thus extending the life of the diesel?

Here are some pictures of the A25 with the current swimming platform and one with how it should look like when is finished.

[Dieselram94]

Did you build the current swim platform yourself? Maybe best to start all over with a new platform? It will definitely be a challenge to get the outboard to turn with the rudder while mounted in the center. Interested to see how you solve that…

[Cappuccino]

Did you build the current swim platform yourself? Maybe best to start all over with a new platform? It will definitely be a challenge to get the outboard to turn with the rudder while mounted in the center. Interested to see how you solve that…

Hi,
Yes I did the platform myself. The platform was done very heavy duty with 8 layers of fiberglass, very thick, very strong.
I will be doing the mold for the lower hull extension with the added length and joining everything all together. For the linkage that is actually going to be the fun part, no biggie, what I do really hate is working with fiberglass .

[DesertAlbin736]

Very nice looking swim platform, although I would hesitate to go with a 25 HP outboard. 143 lbs is a lot of weight to add to the stern in addition to the weight of the swim platform. I'm now a boatless ex-Albin 25 owner, but before that I was a 'rag bagger' with a Catalina 25 sailboat, which with its 1,750 lb lead wing keel weighed more than an Albin 25 and had a similar waterline length and hull speed. It was outboard powered with an 8 HP long shaft Tohatsu 4 stroke outboard which was plenty to propel it to hull speed. 8 or 9.9 HP Tohatsu motors weigh in at about 95 lbs, 50 lbs lighter than a 25 HP and are electric start. I'm pretty sure it's possible to mount throttle/shift/start/stop remote controls up by the helm. Then again I would consider a small portable motor for a dinghy that could double as your emergency propulsion. If you maintain your main diesel engine you should have little to worry about breakdowns. A BoatU.S. tow policy would be worth having. As far as gaining an extra knot or two, Albin cruising is about enjoying life in the slow lane and seems hardly worth the effort to go a lttle faster. Even the 2nd gen De Luxe 'semi-displacement' variant isn't that much faster than the 1st gen full displacement hull.

Here's the outboard setup we had on our sailboat. the bracket mechanism was spring loaded so the motor could be lifted out of the water with minimal effort. If weren't for the fact that the mast was such a hassle to step and unstep for trailering we would have kept that boat.

IMG_5432.JPG

[tribologist]

Very questionable project. There is a gen 1 albin in sweden “Victoria” that have an extended rear and he did not get any higher speed. If anything you probably will reduce the speed by adding weight to the rear. Hard to say since it add displacement too. Even the weight of a full water tank makes it run much better. You could possibly get a few knots out by converting it to a deluxe by building up the hull infront of the transom. There is a drawing on Sjohistorisa.se showing the difference. The lines are available for the original hull and i have converted both hulls to 3D models. I could understand adding a bracket that could hold a 5 hp light engine for emergencies if one had a worn out AD21 with plugged cooling passages or similar. Keep fuel clean, maintain hoses and electrical system and there is 0 need for an extra engine, add rope cutters and keep an extra prop if you are concerned over that but a A25 is not usable as an offshore boat anyway. So many better ways to spent time and $. Getting AC, hot water, bowthruster, autopilot, modern gps and radar, AIS, diesel heater, upgraded trailer. That swim platform looks awesome by the way!