What Happened to My Boat Motor?

10 secrets your mechanic may not want you to know.

Silence may sometimes be golden, but not when it should be pierced by the comforting purr of a boat motor. Thirty minutes ago my boat was humming along to that very soundtrack. Now, its silence is deafening, broken only by the occasional lapping of waves against a motionless hull. Judging by the lack of success of the few troubleshooting tricks I know, this issue may be serious. Time to call the mechanic. Yep, the mechanic. He could be a skilled technician, with plenty of knowledge of my particular engine. He could also be the type of shady dude who’s quick to diagnose a serious problem and hopes I won’t question his assessment, or the labor bill. Then again, he could be a really great guy — who just happens to be woefully underqualified for the job.

Whatever the case, I’m ready. A few weeks earlier I’d spent some time with Larry Hutt and Joel Hanks, two senior instructors at Florida’s Marine Mechanics Institute (MMI). This is where some of the nation’s top repair guys learn how to diagnose the basics before delving into overhauls. Hutt and Hanks have coached me on how to read the most common misdiagnoses. So, if this mechanic’s honest, we’ll get along just fine. But if he’s not, well, I know his secrets.

Secret No. 1: That overheating engine doesn’t call for a new water pump impeller.
Is the impeller really shot? You should be able to get about three years out of it on average. Keep good records, and note if things are prematurely failing. Hanks recounted several stories of engines overheating at higher revolutions per minute, and mechanics quick to change the impeller, when in reality the problem was a simple water restriction. In one case Hanks got tired of touching what he refers to as a “Chia Pet” on the drive. Turns out that the excessive growth was restricting the cooling passages, enough to cause overheating. A thorough scrubbing with a deck brush was all that was needed. Boat owners can also be fooled because of a faulty temperature gauge. Sloppy mechanics will trust the boat’s instruments, whereas skilled ones know to use only reliable shop tools, such as an infrared thermometer in this case.


Secret No. 2: Water on a plug doesn’t instantly mean a blown head gasket or cracked block.
Some mechanics, when finding water on a spark-plug electrode, will jump the gun and replace the head gasket or give the boat motor a complete top-end rebuild. It’s a huge expense. The cause, however, may be as simple as water in the fuel. Ask your mechanic about the integrity of what’s in the tank. Our experts have also seen faulty or inadequate gaskets on hatches that let rain leak directly into the flame arrester and accumulate in the engine. Loose exhaust bellows can allow water to backflow into the engine if there’s a highspeed shutdown, like when you drop a skier or back down on a fish, and an overloaded boat can lower the exhaust elbow height enough to allow water to enter.

Secret No. 3: You don’t need a valve job.
Cheap mechanics aren’t always the bargain they appear to be. Hutt recalls one customer who began to experience serious backfires not long after an oil change by a low-cost mobile mechanic. The same mechanic then diagnosed “a valve problem” and declared it outside his skill set. Fortunately, a reputable tech discovered the oil reservoir had been overfilled by about two quarts and was floating the lifters. “A disreputable guy would have gotten that apart, found nothing, sent the cylinder heads out to be reworked, probably put a set of lifters in it and handed the customer a $1,500 to $1,800 repair bill,” Hutt says. And ironically, he would probably think he had somehow fixed the problem, because he would have had to change the oil in the process.

Secret No. 4: Poor performance does not automatically mean you need a tuneup or a new prop.
There are many overlooked contributors to poor performance. Look for simple answers first, like water in the bilge. At nearly 8.5 pounds per gallon, undiscovered water can seriously sap a boat’s ability to get onto plane or reach top speed. Bottom growth is also a notorious culprit. While the incorrect prop can also seriously hinder a boat’s performance, be careful; our experts have firsthand knowledge of shops incorrectly diagnosing a prop change when the boat had only grown heavier from the reasons above, or from an accumulation of equipment stored on board. Multiple tuneups are often thrown at boat motors that are simply tired and in need of a reconditioning.


Secret No. 5: A misfire at high speed doesn’t necessarily mean the ignition is breaking down.
Your mechanic might say you have “major electrical component failure” when in fact a misfire could be the result of simple corrosion. “When you hear a misfire, the first thing that pops into a lot of people’s heads is maybe the ignition is breaking down,” Hanks says. “I had a guy come into my shop who had already been to four shops previously. He’d gotten a full tuneup, caps, rotor, fuel system and lots of diagnostic charges.” In the end, all the guy had was a bad ground. Check the battery, or any jumper grounds between engines, and make sure you have a solid ground connection. Terminal corrosion, a loose cable or corrosion in the wire can all result in similar problems. Another culprit could be spark plugs. Check to make sure they’re the proper heat range and type. Shady mechanics are notorious for using cheap plugs.

Secret No. 6: Low fuel pressure? It could be something other than the fuel pump.
“I remember a guy in Miami who told me he could change fuel pumps faster than his dealer could,” Hutt recalls. “He’d gone through five in three years.” With Hutt’s assistance, the owner discovered it wasn’t the fuel pumps that were the problem, but a high fuel vacuum that was prematurely wearing them out. Again, keep track of how often items are replaced. Fuel pumps take their unfair share of the blame, but often the problem is a restriction somewhere in the fuel supply line. A new pump might overcome the problem while it’s fresh, making it seem as though it was the right fix, but eventually it will give out from the stress. Ask about the mechanic’s fuel vacuum reading; anything more than 2½ inches of mercury on his gauge is a sign of an obstruction, meaning the pump has to work too hard to pull fuel through the line.

Secret No. 7: The pricey transmission job could be an easy sell, and a bad call.
Both Hutt and Hanks have stories of customers devastated by a mechanic’s diagnosis of a pricey, lengthy transmission rebuild. “They hear clatter, clatter, clatter and are convinced the transmission is shot,” Hanks says. Ask about the condition of the oils. If there’s something wrong with the transmission, they should show signs of burning or charring. Water in the oil will turn it pink and milky. Silver flecks of metal in the oil are another bad sign. Both of my teachers know of transmissions that were making rackets on older engines because the engines were out of tune or, strange as it sounds, because the carburetors needed to be rebuilt.


Secret No. 8: Just because the motor won’t turn over doesn’t mean you’ve blown the engine.
Another common tale from both instructors is that of the “blown engine.” Inexperienced techs quickly diagnose it for one obvious reason — the engine is completely locked up and won’t turn over. The next steps see the tech drop the lower unit, set it in the corner and then start tearing apart a perfectly good engine, instead of simply trying first to turn the flywheel manually. “People take outboard powerheads off, saying they’re blown up, when actually they’ve got a lockedup gear case,” Hutt says. The problem can also happen on stern-drives and inboards. The motor is not necessarily blown; it simply won’t spin over because it’s coupled to the upper part of the frozen drive.

Secret No. 9: The ignition problem could be downright simple.
Hutt recounts the story of one customer coming from another shop with continuing ignition problems, and a long tale of replacing almost everything in search of a mysterious miss. The stator, trigger assembly, switch boxes and six coils had all been replaced by a tech chasing down the problem. The problem still didn’t go away. One look at the key switch told Hutt all he needed to know. It was green from internal corrosion. “I’m not saying I would have caught it initially either, but I don’t think I would have put 1,500 bucks’ worth of parts into it. Somewhere I would have stopped and asked, ‘What am I missing?'” Check that water doesn’t run into the ignition switch and that a rubber boot, if present, is intact. Hanks also suggests inspecting the safety lanyard. If water gets into the works, it can shut down the engine.

Secret No. 10: You might really need that rewiring job he’s trying to pitch you.
Many do-it-yourselfers make matters worse for technicians, especially when it comes to wiring up various electronics. Standards, like those published by the American Boat and Yacht Council (ABYC), exist for a reason. Scrimp, or deviate from the guidelines, and you may be throwing roadblocks in the path of a tech trying to diagnose a problem. “Many times I’ve explained to a customer what we need to do is get this back to proper standards, because I can’t see the problem through the problems,” Hanks says. “It’s hard for us to accurately make a diagnosis if there’s so much stuff that doesn’t belong there.”


So what happened to my motor? Well, before my mechanic even thought about taking it apart, he checked the obvious while I stood watch. Sure enough, he found a loose “wake-up” wire at the electronic control module (ECM). He tightened it up and secured it for $40 and a couple of cold ones. He could have tried to sell me on a new ECM or some phantom ignition part. lucky for him, he didn’t.

Looking For Mr. Reliable
He says, “Trust me.” But should you? Use this quick guide when you’re sizing up marine mechanics.

Ask Around. Word of mouth is perhaps the best indicator of who does good work in your area. Hanks offers this common-sense parallel: “If you had a child, you wouldn’t just drop him at a day care without talking to anybody.”

Don’t Feel Obligated to the Selling Dealer. You’ve already given him a sale. Now his shop has to earn your business. Don’t be afraid to check out which other shops in the area will honor your warranty. Choose who’s best based on service, not misplaced loyalty.

Drop In. Talk to the service manager and verify that the technicians are trained on your specific motor. Then check out the training certificate plaques on the wall. Dates should be current or, at the very least, up to the year of your particular engine.

Test the Waters. Try a mechanic for a maintenance item before you need a major repair. “I’d rather know what kind of work these guys do before I need something major,” Hutt says.

Appearance Counts, Sometimes. A neat shop doesn’t necessarily mean a good one. Likewise, a neat tech is not always a competent one. “What kind of work does he do?” Hanks asks. “That’s what you should be looking at.” How busy the shop is, however, often speaks volumes. A shop that isn’t busy at the height of the boating season is like an empty restaurant at dinnertime. It could be a red flag.

Accept Imperfection. No tech or shop is perfect, and even the best have a bad day. What’s important is to see how the shops handle mistakes. The good ones will promptly acknowledge a mistake and tell you how they’re going to make the situation right.

Appreciate a Showoff. A good mechanic will be proud to show you the work he’s done. Great ones, Hanks says, will make a boat better because they touched it. “I tell students if you do everything 100 percent, you take pride in your work and treat your customer right, why would the customer go anywhere else?”