Repowering Your Boat

Consider these factors when replacing old outboards with newer models.
Fishing boat with Yamaha engines
New outboard engines can provide a world of difference to your favorite fishing boat. Courtesy Yamaha

It’s rare to hear starters grinding or see clouds of blue smoke at coastal marinas and boat ramps these days.

That’s because there are very few carbureted outboards hanging off transoms. Granted, those simpler mechanical engines helped catch a lot of fish over the years, and many are still running strong. But even bulletproof designs wear out eventually. When that happens, you’re left with an important decision: rebuild, re-power with fuel-injected technology or buy a new boat. Before you decide, consider all the variables.

Should I Buy A New Outboard For My Boat

“The first thing I ask customers is if they really love their boat,” says Craig Freeman, the sales manager of ­Barrier Island Marine in Charleston, South Carolina. “If you don’t absolutely love it, it usually doesn’t make sense ­financially to re-power unless it’s a classic Whaler or something that’s been in the family for years. With common hulls, you just can’t get that added cost back out whenever you do sell it.”


Freeman has an extensive checklist he goes through with customers to evaluate the feasibility of repowering. One of the biggest considerations is the extra weight of a four-stroke engine compared with the original. That can impact the ability of the boat to self-bail, and often requires trim tabs to offset the stern sitting lower in the water on initial acceleration. Notched or lower transoms are also problematic with the added weight. Soft or rotted transoms will have to be repaired first. Fuel tanks on older boats should be thoroughly inspected. Batteries might need to be replaced to ensure proper voltage for computerized engines or they might have to be moved to offset the change in weight distribution.

“I never give a quote until I actually see the boat to figure out what else might be involved,” he says. “And I have turned down some repower requests. I don’t want the customer to be surprised or not be able to meet their ­expectations.”

New Outboard Engines Are Heavy

Brett Shields, president of Shields Marina in St. Marks, Florida, is another dealer who pays special attention to the weight factor. He sells Evinrude direct-injection two-stroke outboards, along with Honda, Yamaha and ­Suzuki four-strokes, plus Angler and Sundance boats.


“The biggest question is: Can a boat originally designed for a two-stroke handle more weight?” he says. “As ­four-strokes became more popular, builders changed hull designs accordingly. They added a couple of inches of gunwale height in ­order to raise the deck three inches to ­offset that extra weight. So that can be tricky with an older hull. An extra hundred pounds or more can really affect attitude and overall performance.”

Best Horsepower Options

Matching horsepower is another variable in the repower equation. Shields compares cubic inches rather than horsepower ratings when dialing in a replacement. He also takes into account performance. “I’ll typically ­suggest going to a 115-horsepower four-stroke on a boat with an original 90-horse two-stroke so the hole shots and top end are comparable. The midranges aren’t much different. I do feel the horsepower ratings (on the yellow safety placard) on most boats these days are too high. Think about it. Do you really need to go 70 miles per hour in a 22-foot boat?”

Boat owners who are considering replacing dual outboards have yet another decision to make: Stay with twins or go with a single, ­larger-horsepower engine. Both Freeman and Shields favor the single­ application.


“Today’s outboards are so much more dependable that I’m comfortable recommending a single 300 rather than twin 150s, even for going offshore,” Freeman explains. “The typical problems encountered now are ­ethanol-related fuel issues or hitting something. A single engine costs less initially, it has fewer parts, and it requires less maintenance. The major advantage of twins is better maneuverability, so if that’s critical, stay with dual outboards.”

Labor Costs to Rig an outboard

The labor costs of rigging a new engine vary. If no unexpected problems arise, removing the old engine and mounting the new one can usually be done in a day. A typical labor bill at Shields will run $450. However, material costs for fly-by-wire systems can add as much as $2,500. If the transom needs fiberglass work, the rigging tubes are full, new gauges and controls have to be mounted, or similar scenarios come up, the extra labor required adds up fast. Freeman likes his customers to leave the old engine on the boat so the original wires can be used to pull new harnesses.

So when’s the best time to buy if you do decide to repower? Anytime the manufacturers are running incentive programs, Freeman and Shields say. Historically, turnaround time is shorter in the winter when service ­departments are less busy. There are price differences between brands, so it pays to shop. Extended warranties are now mostly standard. If you do switch from the original manufacturer, plan on replacing all the gauges, controls and key switches, since the old ones are rarely compatible. And according to Shields, outboards are no longer designated by model years, so close-out bargains are a thing of the past too.


It’s a reassuring feeling to step aboard your pride and joy, turn the key and have the engine fire off without ­hesitation. But there are also circumstances when it might be better to say goodbye to an old friend. By ­approaching repowering objectively, you can see if it’s the right choice for you.

Boat Repower Checklist

  1. Crunch the numbers. Does a new engine(s) make financial sense?
  2. How’s the transom? Is it notched or does it show signs of rot?
  3. Does the boat have trim tabs? If not, plan on adding them.
  4. Inspect the fuel tank. Remove any old gas and refill tank before running the new engine.
  5. Calculate the weight differential.
  6. How old are the batteries? Will they need to be moved?
  7. Will the old propeller work?
  8. Plan to replace gauges, control boxes and key switches.
  9. Will wiring harnesses have to be replaced or added? How accessible are the rigging tubes?
  10. Plan for the unexpected when calculating labor costs.