A photo boat gets fitted with a SeaCore-protected MerCruiser 496 Mag HO and IMCO Marine full hydraulic

Story: Gregg Mansfield
Photography: Bryan Linden

For more than 12 years, the engine in Powerboat's photo boat had provided dependable service. Whether it was for a photo shoot on the Pacific Ocean or ferrying a safety crew on a local lake, we could generally count on the big-block to do the job.

But it was around 1,000 hours on the 502-cubic-inch engine where it began to make some unusual sounds. The smell of fuel was a little stronger, and old reliable was, well, just old.

Finding parts to repair the engine was like discovering a shipwreck in the middle of the Atlantic. And judging by the extensive rust on old faithful, it was only hours shy of needing a complete rebuild.

Practically speaking, it was better to spend the money on a new engine and drive rather than try to salvage the stern drive that rolled off the production line when Joan Rivers' number of plastic surgeries was still in the low single digits.

The next engine would need to match the horsepower (at least 400), and the package would have to be durable enough to withstand frequent use in the ocean. When evaluating various engines on the market, one engine stood out: the MerCruiser 496 Mag HO and Bravo One X with the new SeaCore system.

Ideal for anyone who boats in a state that borders the ocean, the SeaCore system is well worth the extra $2,500. Mercury says it does a hard-coat anodizing of the drive and the running gear. Even if the drive is scratched, it will inhibit corrosion, the company says. The package also features stainless-steel components and the motor has a closed cooling system to reduce potential for rust.

Replacing the engine in the 23-foot Nordic photo boat was going to be pretty standard, considering the old motor was built by MerCruiser and had a similar style drive. But every engine swap has its share of minor problems, and this one was no different.

We turned to Teague Custom Marine in Valencia, Calif., to handle installing the new SeaCore MerCruiser. Rigger Dorian Gros did the work, which also included the installation of a new Livorsi Marine throttle/shifter and gauges.

Out with the Old

One look at the engine compartment of the photo boat, and it was obvious the runabout was used as a workboat. The bilge was dark from a lack of cleaning and the compartment wiring had little sense of order.

The first step was to disconnect the boat's batteries and remove the upholstered engine hatch. From there Gros took off the outdrive, which was in adequate shape considering the boat's hard use over the past 12 years.

Gros then methodically removed the fuel line and other lines and wires attached to the engine. With that cleared, the rear bolts that hold the back of the motor to the transom plate were removed. Other supports also were unbolted.

About 4 1/2 hours later, Gros finally had the old engine pulled from the compartment. With the motor gone, he noticed the fiberglass near the motor box on the port side was breaking away. That meant an extra day of grinding, new fiberglass and gelcoat in the spot.

"It could be wear and tear, and it just popped free," he said.

Checking the Systems

With an empty engine compartment, Gros started checking for dry rot and thankfully didn't find any. He also used the opportunity to inspect the wiring and test the boat's bilge pump and blower. Gros removed some extra wiring that must have been left over from a previous repair.

"It's better to do it now instead of having to be a contortionist later," he said.

Gros swapped out the old exhaust tips for a switchable exhaust muffler system from Teague Custom Marine. He rigged all of the wiring so when the engine was installed it was a simple connection.

We also had Gros look at the batteries to find out why they were draining so quickly. It seemed no matter what event we went to, the batteries needed a little extra charge.

Our drivers were pretty good about turning off the batteries, but something in the system was draining them. The rigger couldn't find an easy answer, so we opted to replace the batteries.

The battery of choice was two 1500 Odyssey batteries from West Coast Batteries. With 1,500 cranking amps, the days of wondering whether the boat will start should be a thing of the past.

Steering Clear

We expected the repowered boat to run in the low- to mid-60s, and although it's certainly not the fastest boat on the water, those speeds required a better steering system.

The old system was cable to hydraulic, which meant you could turn the wheel a half-inch before the drive would respond. Our technical editor and lead test driver Bob Teague thought it was best that the boat have full hydraulic steering from IMCO Marine.

With the old engine out and the new one going in, it was a perfect time to add the steering system. Gros had to run lines from the steering wheel at the center-console under the sole (the other method is through the gunwales) to the engine compartment. He also had to drill two small holes on the transom to accommodate the hoses.

All in all, the steering was a fairly trouble-free addition, which will make a dramatic difference when operating the boat.

"The boat is very responsive," Teague said. "That's what you need for a (photo) boat."

Gros also knew that the rams for the hydraulic steering on the drive would bump into the boat's brackets that support the swim steps, so he modified them to allow the drive to move freely.

Power Ready

Now the boat was ready for the MerCruiser 496 Mag HO to be installed. The existing motor mounts were perfectly positioned and in good shape, so Gros bolted down the rear main mounts, and then tightened up the feet.

The main concern was making sure the engine was properly aligned so it could accept the new outdrive. With the motor in its correct place, the drive was installed but not before Gros had to resin the transom cutout to prevent dry rot. Aligning the engine and drive is where do-it-yourselfers tend to get into the most trouble.

"It depends on how much knowledge you have," Gros said. "You have to have the right equipment and knowledge or you can mess stuff up."

With the MerCruiser firmly in place, Gros started making the electrical connections to the engine. He got the fuel line hooked up and then turned his attention to the exhaust.

The exhaust for the new engine was offset differently, which meant Gros had two options: He could either drill new holes in the transom and patch the old ones, or he could create new S-pipes to get rid of the exhaust.

Gros wisely picked the latter and mocked up some pipes. Using old pieces and a tack welder, he created a sample pipe that he was pleased with. Then Teague Custom Marine custom made the S-pipes from stainless steel. The connection from the header to the switchable exhaust went without a hitch.

"Connecting it can be a bear, but if you've done your work right, it's pretty simple," Gros said.

From there it was pretty routine as Gros bled the steering lines, reconnected the batteries and put the upholstery back into place.

He double-checked the MerCruiser engine and IMCO Marine steering to make sure nothing was overlooked.

Old Reliable

Once we fired up the photo boat on Arizona's Lake Havasu, it was obvious that "old reliable" was back better than ever. Gone were the strange noises that we took for granted with the old engine.

The new 425-hp engine delivered smooth and consistent power, pushing the V-bottom to a top speed of 67 mph on GPS. And we had no more worries about the engine starting or even giving out while running it for photography.

The change in the steering was very noticeable. At speed, the full hydraulic steering from IMCO was silky smooth and instantly responsive. With a large metal tower on the Nordic, the boat has a slight tendency to wander. Thanks to the steering system, it was easy to put the boat back on a straight course.

Repowering the photo boat wasn't cheap, but it was money well spent. We expect the boat should provide us another 12 years of worry- and trouble-free service. P

Click to enlarge.