Hi, new to the forum, in fact I havnt owned a boat since I was 20 years old. (Please don’t ask how long that was)

Anyways, I bought a 25’ Formula with a single big block. I love the boat and it runs great. I’ll be running this in a big bay and on the intercostal.

I was thinking of bolting some kind of small transom on the back. Maybe a fold out design to except a small outboard. I could keep the small motor in a case in the cabin. I’m talking like 3-6 hp. It would be just emergency. I know it would be very slow, but better than swimming.

Is this crazy? Is 3-6 hp too small to push a 5000# boat? I’m kind of thinking there must be something wrong with this idea or it’s allready been done.

Totally separate question. What is the consensus on the “one way” drain plugs?

Also, do I need a separate cooling system because of breckage water? Is it practical to install on an older boat?

If the idea was a good one, you'd see other people doing it. You see it once in a while, but its usually like a 20hp+ and on fishing boats. Get a Sea Tow membership.

I don't know any specifics about the one way drain plug, but I've never seen a regular drain plug fail.

Brackish water??? It will eventually take its toll on on the exhaust and engine internals. If the boat is getting pulled out of the water or put on a hoist, flush it with fresh water.

Actually, I was hoping no one would see it. If the transom would fold up under the swim platform and the motor was in the cabin. (Maybe in a pelican case) 20 hp would be probably getting pretty heavy to handle, but maybe. One reason I think you never see it would be most people would just get a twin engine. I’m going to look into the sea tow thing, but that’s kind of like AAA membership. You call them and a tow truck shows up in 5 hours.

When I went for a test drive of my boat, the owner left the plug out. So yes, the plug didn’t fail.

My boat will mostly sit tied to a dock. The guy I bought it from said they have heat exchangers that keep the sea water out. He also mentioned a port that you can wash the engine with it in the water. I’m not talking about the little muff that clamps on the lower unit. He said it is up in the engine bay. Anybody got opinions on that setup?

Closed cooling is a wonderful upgrade.

I don’t want to dampen your enthusiasm but keeping that boat in brackish water will be a huge headache for you. Rot in the motors, transom assemblies, drives, etc……. I would get a boat with outboards and ensure you have the BEST boating experience you possibly can. If you’re keeping it in the water I’d get a SeaTow membership - rigging something up isn’t a solution. No idea about one-way plugs but a good old fashioned brass plug will last longer than you……

Is the boat at least bottom painted??

Sure, they have heat exchangers aka closed cooling systems. They cost about 3-4k plus install labor Marine Closed Cooling Systems

I would definitely NOT go with a flapper valve, or any type of "one way" drain valve, if you are keeping the boat in the water. It WILL fail at some point. IF the boat get's water in it, it's not going to push it's way out. If you are going to keep a boat in the water, which really isn't a great idea with a typical performance boat...
...you need good strong batteries to power the bilge pump. Shore power to keep them charged, or perhaps solar charging.

Follow up question, the bilge pump on this boat works great…….when I turn it on. It turns off when I turn it off. I was led to believe it was automatic. Was I misled? I will have shore power and water on my dock. The boat came with a slick trickle charger installed. So in theory, the pump could keep it empty, but I can’t leave the pump run dry. The pump has a round disc that is wired to it that looks like some kind of solid state sensor, but apparently doesn’t do anything. Am I missing something?

Do your local waters have either Sea Tow or Boats US tow services? The price of a small outboard kicker may pay for a couple years of memberships for you.

There should be a float switch in the bilge that turns the bilge pump on in addition to the manual switch on the dash.

That sounds like a float switch. Throw some water in the bilge with the switch turned off and see if it comes on. Boats used to have a switch on the dash for the bilge pump with the indicator manual/off/automatic. Now days it’s on/ off, with the automatic float sensor wired directly to the batteries so there isn’t too many connections to fail.