Building My Dream Yacht From Scratch Pt 5 - Innovative Inboard-Outboard Engine Mounting!

In todays episode we've got 500HP worth of outboard engines were going to mount inboard our pontoon yacht! What could go wrong!?

Music:
Fareoh - Cloud Ten

[timothymccloskey]

Mechanical design engineer here. I work in the steel industry. We have a little saying: “don’t make bathtubs” - means never weld something that could potentially pool water without putting in a drainage hole.
Your engine mounts look nice and sturdy to me, but I’d put a little drainage hole in the bottom there.

[johnlayl]

Don’t forget to put something like Tef Gel or Anti Seize on the bolts used to mount your outboards. Aluminum and steel will create galvanic corrosion.

[tomspontoons]

Hey!! Thanks for the shout out guys! I’m here if you ever need some help with the project.

[lukeeverett]

Hey Legends, I'm was a Marine Engineer in the Australian Army, I worked quite a lot on out open water dual hull SharkCat. It had twin Mercury Verados as well.
I would investigate the FSU (Fuel Supply Units) on both engines before you launch into the water. This job is not too hard to swap the FSU out, but you need to be on dry dock.

[gladius_]

Chris I think this build is awesome but I would recommend a bow thruster. It going to make moving that beast in tight areas.

[ryancollins]

Just a thought Chris, you should consider mounting a bilge pump inside the hot tub compartment before you mount the hot tub shell. I think your future self will thank you for providing a way to vacate the water that may or may not get in there.

[denontour]

Hi Chris, I think that a Transom Plate across the entire rear would be the way to go, since this will transfer the pushing force of the engine to the boat more evenly. Single transom plates will cause more stress on your structure ...

[taconerd]

Im a marine outboard technician. I wouldnt have gone with used mercs but thats more of a personal preference. Make sure all the services are done. Id go down the service chart and do each and every thing regardless of the previous owner or seller said they were done. Id also get in contact with a merc dealer and make sure all the recall work was done. Also idk what the salt content is in the water over there, but id also replace every anode.

[RachaelSA]

You could add a "skid plate" along the whole bottom, joining the 2 inner pontoons from the hottub enclosure all the way to the transom at the back, and it would add a lot of buoyancy, stability and storage, and it would be a big flat trimaran and give you a better flow of water over the propellers.

[bendooley]

Make sure your hot tub has its own bilge under it. Nothing like getting a leak you dont know about to ruin your trip or your boat.

[wingshonda]

Don't forget drain hole on bottom of engine mount

[davessparetime]

I still think you should finish weld the bottom strakes that don't connect between the pontoons. Buy two engines setback brackets and tie both engine mounts to each other as a solid Transom. You need a good two to three inch thick transom that ties to all four of the pontoons.

[nick-hq]

200kW per engine is a lot of power. Don’t want to sound pessimistic, but in my case 150hp (100kW) engine ripped out a similar welded-in engine mount from my “conventional” alu-boat after a few years. I’d really consider additional struts and braces to ensure the lower weld seam does not crack the pontoon. Thinking out loud.

[TGoff-fzyh]

It's like the flybridge off a yacht, on a dock, with motors. Admittedly, the flybridge is always the best place to be.

[kevinsellsit]

Always a pleasure to be here and glad to see you hot glueing more Aluminum and horsepower to (our) party boat.

[JoakimBergh]

You should look into maybe getting a manual or a hydraulic jackplate for your outboards. If you want the pontoonboat to go faster, that might be needed.

[Alex.]

As a marine technician, all I can say is good luck with two 1200 hour verados. Not the move I would have made, but, it'll make for good content 😂

[DonFarmer-hqsw]

This stage would be an excellent opportunity to create some plates that lock all four pontoons together then. Mount the engines 😊

[raptorheli]

You can buy the steering system from seastar to have them go whatever direction you want independently fyi.

[walterscott]

Your lower cavitation plate should be 1/2 to 1 inch above the bottom of the pontoon. Make sure the TOP of your motor mount is very strong.