If you are thinking about repowering your boat, think carefully. This is not to say you shouldn’t repower, just that you should spend the appropriate time and effort understanding the scope of the project. Time spent in this evaluation process can save you thousands (often tens of thousands) of dollars and a great deal of disappointment.

Let’s agree at the outset that we’re not talking about home-brew restoration projects. The point of a restoration project is doing the restoration itself. Instead, we are talking about improving the power situation on your beloved boat.

Certainly, a repower project makes sense if (1) you have a deep sentimental attachment to the boat, (2) the hull is in great shape, (3) the loan is paid off and (4) you fully understand that on most inboard-powered boats the repower project will add little if anything to the boat’s resale value should you have to liquidate it on short notice, although chances are it will make it a more attractive purchase.

The case is slightly different when you are considering hanging new outboard motors because the motors are usually priced separately in the resale evaluation and replacing them can be relatively straightforward. We’ll return to outboards later in this column.

Back to inboards. Typically your boat will be 10 to 20 years old when you decide to repower, assuming you’ve kept up with routine maintenance along the way, such as changing the cooling system components before they’ve rusted out.

The least expensive part of the project may be the purchase price of the engines themselves. Once the old engines and transmissions have been removed (often time-consuming because the mounts have become rust balls), you’ll have access to the original fuel tanks. They are probably in need of replacement too. Chances are they are no longer stock items and will have to be made to order.

Next you may discover that the engine beds need replacing—especially wood beds or glass covered wood. The same is true of the tank mounting structures.
Certainly the engine harnesses should be replaced, and you may have to replace the engine instruments. And, as long as you are behind the panel anyway, you’ll want to clean up the rest of the DC electrics that have become a Gordian knot with all the tinkering you’ve done over the years.

If the boat has AC electrical power, you should also inspect the AC components and runs too. These should be brought up to modern ABYC and NFPA specs for safety. Most of the DC and AC electrical systems I’ve seen on 20-year-old boats don’t come close to meeting modern standards.

Sometimes just finding parts can be a challenge. A couple years back I was involved in a repower project on a 1968 Luhrs 32. Replacement engines were easy to find, but the Paragon V-drives were long out of production and switching to new drives would have required changing angles on the shaft log or lifting the deck. Finding someone who could recondition the Paragons (and finding a replacement water cooling case) took time and money. On this project we ultimately replaced the shafts and struts anyway. This is also a good time to replace control cables.

On older boats you’ll want to inspect carefully all the engine-related through-hulls and replace any gate valves. The same goes for the raw-water strainers.

And, of course, you’ll also want to pay close attention to the dimensions of the new engines and their cooling hardware. While blocks haven’t changed much over the years, the fully accessorized engines tend to be longer and higher. On the Luhrs project mentioned earlier, we had to notch deck support stringers and reinforce them with steel straps to provide room for the cooling elbows while maintaining deck strength.

You get the idea. Repowering an old inboard is a lot more complicated than simply dropping in new engines.

While all of this may sound a bit grim, it is not my intention to discourage you. The project can be fun. It will involve back-of-the envelope engineering, hunts for suppliers, decisions of the heart and pocketbook, and experienced yard personnel willing to work with you early on and keep you in the loop during the project.

Very few yards will give you a fixed price on the job, because they know they will run into the unexpected.

Of course, the younger the boat and the larger the original production run, the easier the repower. (But a recently manufactured, high-production boat shouldn’t need a repower unless it was winterized improperly or suffered some sort of catastrophic failure.)

Outboard Motors
Outboard motors usually are easier to replace, especially if you are staying with the same manufacturer and size. Two items can be problematic and must be considered. Older outboard-powered boats often have wet transoms—that is to say water has seeped into the mount plate holes and softened things up. Make sure your transom is healthy. If not, it must be repaired first.

If the make or model engine is changing, say going from Mercury’s Optimax to the company’s new four-cycle Verado, the mounts must be replaced. Also, a 225 hp Verado is about 130 pounds heavier than a 225 Opti. So upgrading to Verados from Optimax outboards can shift your center of gravity aft (unless you redistribute other fixed weight, like batteries) and that shift will change the boat’s static and dynamic characteristics. Those changes are not necessarily bad, but need to be understood.

So bottom line—do your homework. A repower project can be fun and it can give new life to that perfect old boat. Don’t be shy, ask plenty of questions, ask the yard for references and check them. Realize that the best yard isn’t necessarily the one that promises the quickest turnaround with the lowest shop rates. Your best choice will be the yard whose earlier repower customers were reasonably happy with their experience, had most of the possible downside items explained before work began and have had the yard’s support after the installation.