Trouble-shooting your propulsion system’s mystery maladies

Everything checks out fine in your engine. Yet, you aren’t getting the performance you paid for — or worse yet, you aren’t even moving. What’s wrong?

Everything might look fine in the engine compartment, but that doesn’t mean there’s no mechanical problem capable of stopping you cold. Sometimes, problems lie beneath the surface — of the water, that is -- outside your boat.

For instance, take the story of one guy who moored his go-fast boat overnight in a marina, next to several 100 foot mega-yachts. All seemed well with this upscale picture until the next morning, when Mr. Speedy fired up his boat’s twin 454 stern drives, woke up everybody, shifted into forward and went ... nowhere.

It seems one of the mega-yachts hadn’t been properly grounded electrically. Mr. Speedy’s twin outdrives became sacrificial zincs -- and they parted company from the hull.

Before you start telling me the one about the guy who supposedly took off on a cruise in his trailerboat with the trailer still attached, I must tell you that the corroded stern drive story is absolutely true. Perhaps it’s unlikely this will ever happen to you, but your boat may experience related problems that keep it from moving.

Spin City

Most of the reasons a boat doesn’t move when urged to do so are pretty cut-and-dried. For instance, a propeller nut might have backed off: The propeller stays on while the engine is in forward gear, but it spins right off in reverse.

In this case, the importance of retrieving that prop is directly related to its cost. You wouldn’t believe the lengths people will go to when they want to locate a stainless steel prop — and you wouldn’t believe how many people think they can retrieve a stainless prop with a magnet because "it’s not aluminum."

Do You Have Cable?

Shift cables will eventually break, and they’ll do it right at that spot you’ve noticed getting more and more cracked.

Maybe in the back of your mind, you’ve meant to replace the cable, as shifting has become more difficult and erratic -- but your priorities got skewed. Better change them now: Otherwise, you’ll soon notice that the bow of your boat is measurably shorter, when the engine won’t shift out of forward gear and you hit that immovable pier.

Shaft’s Big Score

One interesting problem that’s now affecting many boaters stems from the quality of a few metal parts manufactured during the 1980s. During the "Me Decade," the quality of stainless steel used in some engine driveshafts was reduced, perhaps for cost reasons.

On driveshafts where this lower-grade stainless steel was used, you’ll notice that just below the water pump impeller, there’s a shaft seal that seems to score a circle in the driveshaft, not unlike a glass cutter. It etches and etches — then, at the worst possible time, you’ll accelerate and the engine will race, but you’ll go nowhere.

You’ll say to yourself, "The prop’s on, the gearshift works, so what the heck could be wrong?" All the while, you’ll notice that the pump is still pumping water: That obviously means the driveshaft’s intact, right?

You’d be wrong. The driveshaft broke, just under the impeller.

Happily, today’s driveshafts are crafted from a higher grade of stainless steel. If you replace the old one with a new driveshaft, you’ll probably never experience this problem again. The bad news is, you’re still looking at a $600 bill to replace the part and fix the problem.

When you’re looking for reasons why your boat won’t go, remember that not all propulsion problems start in the engine room. Take a systematic approach to trouble-shooting by investigating every major component -- from the starter to the powerplant to the prop.

MerCruiser 454 MAG MPI Horizon Stern Drive

When performance counts, MerCruiser’s newest stern drive delivers.

The 454 MAG MPI is the first of two new stern drives based on MerCruiser’s technically advanced Horizon engine. The Horizon series inboards have already proven extremely popular, thanks to their "hassle-free" design and minimal maintenance requirements.

Like its inboard cousins, the new 454 MAG MPI Horizon stern drive is billed as "virtually maintenance-free," requiring only periodic fluid checks and seasonal oil/filter changes. While most stern drives require periodic maintenance after every 100 hours of operation, the 454 MAG MPI Horizon stern drive won’t need to visit the shop for three years (or 300 engine hours, whichever comes first).

Available with a Bravo 1, Bravo 2 or Bravo 3 drive, the 454 MAG MPI Horizon produces 385 hp at the prop shaft. The Bravo 1 Performance drive -- developed for conventional and stepped hulls where drives are running close to the surface -- features low-water pickups that provide a steady, uninterrupted supply of water.

The closed cooling system offers long-life five-year coolant, ceramic-coated exhaust elbows and manifolds, an engine flush system and constant-tension stainless steel hose clamps.

For sure starts and economical operation in a wide range of conditions, the Horizon power-plant utilizes a digital ignition system and a high-output 65 amp alternator. Other standard features include platinum-tip spark plugs, high-temperature spark plug wires and stainless steel ground studs.

Buyers get a three-year warranty against corrosion, a one-year factory warranty on the entire engine and two years of extended Mercury Product Protection.

Contact: Cap Sante Marine, Ltd.; info@capsante.com