M aybe you’re a tournament bass angler, and every second counts. Perhaps there’s a thunderhead on the horizon, and you need to get home ASAP. Or, maybe you just plain like going fast.
Whatever the reason, many boaters are concerned with—possibly even obsessed with—getting their boat to run as fast as possible. And with a few simple steps, just about anyone can add a mph or three to their top-end. You say you like 50 mph a whole lot more than 48? Here are three things for you to consider.
Among all the variables that impact a boat’s top-end, weight is one of the most significant. That’s why builders split hairs to shave every pound possible from a boat, and it’s why you should too, if you want to maximize speed.
Let’s start off by recognizing that we all tend to load down our boats with a bunch of gear we think we need. But, just how much of it do we actually use on a regular basis? Do you really need to carry that second anchor? The box of bucktails you haven’t used since the 1990s? That extra case of chilled beverages? All that stuff adds up.
Now, consider some “fixed” poundage, which most boaters never even think about. Bottom paint, for example. A coat of bottom paint usually shaves about one mph off a 20-something boat’s top-end. Contrary to popular belief it’s not because the paint has a rougher surface than fiberglass—it’s because of the added weight. Or, consider seating. If two of you are going fishing and your boat has four pedestal-mounted seats, those two extra seats are hitting you with a weight penalty for no reason.
Finally, remember to account for “wet” weight. Things like full water and waste tanks, or livewells, may or may not be necessary depending on how and where you use your boat. If they aren’t, minimizing tankage can save gobs of weight. Remember, water weighs in at around eight pounds per gallon and fuel at around six pounds per gallon. That may not sound like such a big deal, but think about it. A full 20-gallon livewell adds a whopping 160 pounds to your boat’s weight.
Now add up all of the above, and subtract it from your boat. You could easily shed 200 pounds or more—and in doing so, gain at least a mph or two at top-end.
Propeller pitch is, to a large degree, what determines the maximum rpm your engine will turn. Before we dig into the why and what to do about it, let’s make sure everyone’s on the same page and understands exactly what pitch is—the theoretical distance a propeller would move forward with one rotation, if there were no slippage.
An easy way to visualize this is to think of a regular wood screw. Some have threads such that a single rotation will creep the screw deep into a board; others are threaded such that a single rotation only takes it half as deep. That’s a reflection of the screw’s “pitch.”
Of course, with a boat propeller there always is slippage. On top of that, boats have variations from one hull to another. After being purchased, a boat’s weight varies because of equipping, painting, and other factors such as those mentioned above. The weight differential also affects proper pitching. As a result, there are an awful lot of improperly-propped boats running around out there.
If your boat’s engine already spins up to the manufacturer’s maximum rpm rating (without any ventilation from over-trimming, of course,) then your prop’s pitch is right on target. But let’s say you have an outboard rated to spin between 5,500 and 6,000 rpm. At wide-open throttle it turns 5,600. That’s in the recommended range, sure, and won’t cause your engine any harm. But it’s on the low end by a long shot. You could subtract an inch or two in pitch, your engine’s maximum rpm would jump up by 150 to 200, and top speed would go up by another mph or two.
Trim is one of those things everyone thinks they understand perfectly, but is often misunderstood. When a boater is trying to milk each and every mph out of his or her rig the most common practice is to trim the engine up as far as possible, period. Keep on raising it until the prop starts grabbing air and howling, right?
Not so much. On some boats, yes, maximizing trim does maximize speed—but not on all boats, and not in all cases. You also have to bring sea state, weight distribution, and an individual hull’s traits into consideration. Trim also affects running angle, which is also affected by all of the above factors. And yes, running angle affects speed.
There’s no simple answer to the above equation, because it changes. Are you running into the seas? With them? Are they on the beam? Is it glassy-calm? Is your 300-pound brother-in-law Bubba currently sitting in the bow? All of these ever-changing influences play a role.
There is, however, one sure-fire way to find the right trim position to maximize speed. Step one is just what most people already do: find that point where your trim is maxed-out and prop starts ventilating, then drop the engine back down a notch.
But don’t stop there.
Click down the drive in the smallest increment possible, while eyeballing the GPS. Give it a few seconds to reflect any change in speed, then click it down another notch. Continue the process until your speed drops, then bump the trim back up a notch. This may happen at the first increment, or it may not happen until the fourth or fifth.
Along the way, your GPS will show you which trim setting maximizes your speed. Note: If you’re doing this in a high-speed situation, such as on a 60-plus mph bass boat, you should have a passenger watch the GPS for you, so you don’t have to take your eyes off the water.
You say yes, you want your boat to go faster? Consider these three factors, nail the throttle, and hold on to your hat.
Email Lenny Rudow at
Email Lenny Rudow at [email protected]