How to Repower and Revive That 'Old Boat'

With a technology upgrade, "I feel as if I have a new boat."

October 31, 2025 By Brenton Roberts

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Coolers were loaded, truck packed, just needed to trim up the motor... no dice. The inner mechanic went to work: Battery good, relay good, trim pump… not good, a pain of a fix on my particular outboard. Luckily, a friend loaned us his boat and saved our vacation, but this is when I knew it was time for repower. The engine on my 2004 Hell’s Bay Whipray was 21 years old, becoming one problem after another. Reliability just wasn’t there anymore.

My boat is a technical poling skiff, specially designed for the shallow water fly and light tackle fishing I like to do. It’s powered by a 40-horsepower outboard. But even on a rig this simple, there’s background assessment and research to undertake before swapping out for a new powerplant.

First, on any older boat, is to determine if the hull is still structurally sound. Closely inspect the transom and the rest of the hull, looking for stress and spider cracks around the engine mounting bracket, warping, evidence of delamination or anything else that suggests structural trouble. Don’t forget to look inside the bilge, too. How do the stringers look? What’s the condition of the fuel tank? Anything in question should be assessed and repaired by a professional.

Yamaha outboard motor. — The writer’s selection of new power for a 21-year-old skiff took weight off the transom while restoring reliability and performance.

Once determined that your boat is ready for new power, it’s time to decide the route you want to go. It’s hard to go wrong with any of the outboard brands nowadays; all manufacturers make a good product. Start with considering your application and how the motor will fit your needs. Looking for high performance to be the first to the fishing spot? Looking for the best fuel economy for long-distance runs? Do you fish solo? Or is the boat often at full capacity? Maybe you need to go up in power, maybe even down. For me, I was going to stick with a 40-horsepower engine. The lighter engine, the better, when it comes to my application, so shaving weight was the goal all the way through. More weight on the transom will increase draft, which I want to avoid.

I ultimately went with the Yamaha F40, trimming 34 pounds off my transom from the previous motor. It doesn’t sound like much, but every ounce counts when your hull only weighs 500 pounds.

Another thing to consider is controls. If sticking with the same manufacturer, you may be able to use the same controls. If switching brands, controls will need to be replaced. Many new controls have integrated technology that syncs with your new motor, making the switch mandatory. Steering must be included in your repower assessment. In my case, I had cable steering originally, a common system in 2004. But times have changed, and hydraulic steering is much smoother.

If planning on sticking with your steering, give it a close inspection. How do your hoses or cables look? Any corrosion around the ram or at the helm? How about the fittings? And the biggest to consider, will it fit your new outboard?

It’s worth consulting a professional if you plan on ordering your new steering kit yourself, as hose length, ram mount and other factors play a role in the fit. The shop installing your new motor will get you taken care of. Not only was my cable steering on the way out, but it wouldn’t fit my new motor, anyways. I opted for a new, all-in-one BayStar steering kit, tailored for my class outboard. The switch was easy.

Prop selection is another vital part of the repower process. To start, take note of the dimensions and pitch of your previous prop. These can be found on either the prop barrel or the hub. The first set of numbers is the diameter, the second is the pitch. You may be able to even keep this prop, depending on the hub splines. If not, you have a baseline for selecting your new prop.

Let’s break down pitch. Pitch is the number of inches a prop would theoretically move the boat forward in one rotation. For example, a 12-pitch prop will move the boat 12-inches in one rotation. This will affect the rpm’s your motor can turn. A lower pitch is like a low gear on your bike: acceleration will be significant, but top end performance may be lacking. This is flip-flopped for high-pitched props. The correct prop should allow your rpms to fall within the manufacturer’s recommended wide open throttle range, which can be found in the owner’s manual. Yamaha suggests between 5,000 and 6,000 rpm for my motor, so aiming for 5,500 was ideal. Lots of advice can be gleaned online, but don’t neglect to consult your local certified outboard mechanic to help select your new prop. There’s a good chance they’ve repowered a boat like yours and can give an idea. If you’re lucky, they may even have a few props on hand that you can try, to help find the correct one.

With the boat in the shop, it’s worth looking at updating other systems. To start, the electrical system is a good thing to check out. Corrosion common in the saltwater environment can cause shorts, issues with electronics and worst case possible, a boat fire. Replacing battery cables and battery switches is a very smart move on any 20-year-old boat.

With a new motor on the back, I felt obliged to update the outdated motor on the front. Sticking with the times, I replaced an old hand-control Minn Kota Riptide trolling motor with a new Terrova Riptide and shaved off another 15 pounds. I’m usually a man of simplicity, but boy is that Spot-Lock technology nice to have, especially in high-current situations. Keeping with the premise of saving weight during this refit, I knew lithium batteries were a necessity.