"My boat should be faster!"
Thinking of buying more motor? Don't jump to that step just yet. There are a few small tweaks you can make to possibly get more from your current setup than what you are right now.
I'm a member of several fishing/boating forums on Facebook and one of the most common complaints is that their boat doesn't go fast enough despite having what seems like a more than adequate motor. It's surprising how many people start off with just being happy to be on the water but then wanting to wring every bit of speed out of their boats that they can. Unfortunately, many do not understand the "tricks" necessary to do this, and many just think the simplest route is to upgrade to a bigger motor.
Buying a new motor certainly is a way to speed up your boat, but it's the most costly and inefficient (and possibly illegal and unsafe!). It's expensive, it adds weight, and it may not fully address the problems that are slowing you down to begin with. And soon, you'll find yourself saying, "I have all this horsepower and my boat only goes 18 mph!"
In order to add speed to your boat, you have to take a moment to understand the causes that slow your boat down to begin with, and identify and fix those that can be corrected, and minimize those that can't.
Let's look at my boat in particular...a 1542 flat bottom jon. Big enough to fish out of comfortably, it just took a while to get anywhere on the lake with it.
I started a while back with a 7 hp motor. I knew it would never be a speed demon with this setup, but I was fine with that at first. So, off I went, Chinese motor on the back, and was happy. Until I realized I could not get away from the traffic near the boat launches, which were at either end of the lake. The middle was where you could truly fish privately and away from people, but with 7 hp moving at 8-9 mph, getting there was just not realistic unless I wanted to be out all day. 13-15 miles per hour would have definitely helped me get the boost I needed to reach the middle of the lake, but I didn't know if I could reach that speed on 7 hp. I knew it would be a lot to ask...
I tried everything to gain even a little more speed...new prop, raising and lowering the motor, trimming, and even a hydrofoil. The one improvement was a change in weight distribution, but it was obvious that the only real answer was an upgrade. So, I moved up to a 9.9.
This was much better, but still pretty slow. Top speed was about 9-10. So, I added a hydrofoil and that helped (sometimes they don't) and got me to 11 mph. It still took a long time to get to the middle of the lake.
Finally, I found a 9.9 Johnson with a 15 hp carburetor. This was much better. I was now able to top out at 15 miles per hour. The boat felt faster, and it was getting up on plane nicely. Which led to the first bit of tuning that I needed to do, and the most basic one that trips up a lot of boat owners.
Prop Pitch
It had an 8 pitch prop, however, and at times it ventilated and lost grip. The engine revved high and didn't really seem to make the speed it sounded like it should...lots of revs, not as much forward progress.
Think of prop pitch like gearing in a car. The lower the number, the lower the gear. Too low of a pitch is like trying to drive in 1st gear all the time. While you'd have incredible pulling power, you'd only be able to go 25 mph or so, and your engine would be redlining at that speed. Great for yanking stumps out of the yard, not so great for cruising on the highway.
I finally settled on a 9 pitch and this seemed to work best. RPMs dropped noticeably, and the top speed went from 16 to 18. I was very much happy with this setup, especially after jumping too far and trying the 10 pitch and actually losing a MPH because of it. But, in a minute you'll see why I might revisit that 10....
So, I ran it this way for a while until I decided to try something out...I also have a 12 ft flat bottom jon. I decided to do the foolish thing and put the 9.9 (remember, with a 15 hp carb) on the 12 footer, expecting it to tear down the lake like a scalded cat. Keep in mind that the 12 footer was rated for 10 horsepower, but I would be pushing it with at least 13-14 from the modified 9.9.
Surprisingly, it didn't go as fast as the 15. And at first, I couldn't figure out why. It topped out at about 16 mph, and when it did, I got tons of spray and the boat just generally didn't handle well at all. But, what I did notice was that when it hit choppy water, it seemed to be much happier. The hull was "sucking down" to the top of the surface and causing drag. When you hit the chop, it released and sped up.
Surprisingly, it didn't go as fast as the 15. And at first, I couldn't figure out why. It topped out at about 16 mph, and when it did, I got tons of spray and the boat just generally didn't handle well at all. But, what I did notice was that when it hit choppy water, it seemed to be much happier. The hull was "sucking down" to the top of the surface and causing drag. When you hit the chop, it released and sped up.
So I figured the best course of action was to trim out, to try to get as much of the hull out of the water as possible. I went out two notches on the trim and this helped a bit, but not enough to make this a viable setup. 15 was about the max possible speed for this boat. A 9.9 is likely the best setup for this boat, hence the 10 hp rating.
Here's why...the first immutable law of boat speed: hull design.
Motor height also makes a difference. Finding the right driveshaft length to match your boat is important, and if there's a mismatch, the engine can sit too low in the water, causing excess drag, or it won't reach deep enough into the water, causing prop ventilation, cooling issues, and other problems. A jack plate can correct for a driveshaft that is too long, but may bring its own set of problems.
All of this illustrates how much each of the factors depend on one another, and also illustrates how much you have to be a tinkerer to get the optimal setup from your engine.
Sometimes people see my minimal setup on my boat and tell me, "You need to add a casting deck to that! You need to permanently mount your swivel seats!" Or some other such suggestion to improve my boat to suit their needs. There's a reason I don't do that...
Another thing that will speed up your boat is to get rid of anything unnecessary that you're carrying with you. I used to carry a bunch of extra stuff that I found I never used...a whole milk crate full of "fishing equipment" most of which never got touched. A set of scales, three marker buoys that I never used, extra fishing reels, etc. Granted, it is better to have and not need instead of need and not have, but if you're selective with your equipment, there's no need to weigh your boat down with unnecessary gear.
No chance of rain? Leave the extra rain gear home. Plan on staying in motion most of the time? No need to take the anchor. Staying near the launch and using your trolling motor for the entire trip? Leave the kicker at home. Only fishing for bass? Don't bring the box with the muskie lures.
Lithium batteries are almost always lighter than lead acid, and these days, not much more expensive. Further, a lead-acid's capacity-to-weight ratio is not even in the same ballpark as a lithium.
Here's why...the first immutable law of boat speed: hull design.
Hull Design
On paper, the lighter-weight 12 footer should be faster than the 15 with the same engine, but it's not. Remember, the 15 was able to achieve 18 mph (and the gains are not over yet) with the modified Johnson 9.9, but the 12 struggled to reach 16. That's because a larger percentage of the hull was dragging in the water.
In the pic above, both boats were photographed from the same distance, so the size should be relatively to scale. Starting at the stern and drawing an imaginary line across the bottom of the boat, almost as much hull is "in the water" on the 12 as there is on the 15. The bow rise on the 15 is much more gradual and starts further back on the hull. The 12 is rather abrupt and leaves a lot of the hull in the water.
That's an easy problem to identify, but not an easy one to fix. The 15 is literally designed to be fast. The 12 is not. So, a decision must be made...can I be happy with what I have, or is it time to trade? Since I got the 12 for tiny creeks and rivers, occasionally being pressed into service on one of the local lakes, I am very happy with the 15 mph "comfortable" top speed, especially since I have the 15 footer as my main boat. I plan to find an 8 or 9.9 hp to use on the lakes with the 12 footer eventually, but there's really no hurry.
After experimenting with the 12 footer, I put the Johnson back on the 15 footer and the next week, took it out on the lake. When I opened it up to full throttle, something seemed different. It seemed...faster. A check of the GPS had confirmed it...I was now going 20 mph. Of course, I was happy, but how did this happen?
Remember when I adjusted the trim out, trying to get the hull of the 12 footer out of the water? Well, I never put it back...
Trim is the angle of the boat's motor in relation to the hull. Trimming the motor in lowers the bow, trimming it out raises it. Generally speaking, raising the bow gets more of the boat out of the water, resulting in more speed. Of course, if you go too far, then the boat will plow with the front way too high. Like anything, you can have too much of a good thing. I had messed with the trim before, but never with this prop.
 |
| 15 top, 12 bottom |
That's an easy problem to identify, but not an easy one to fix. The 15 is literally designed to be fast. The 12 is not. So, a decision must be made...can I be happy with what I have, or is it time to trade? Since I got the 12 for tiny creeks and rivers, occasionally being pressed into service on one of the local lakes, I am very happy with the 15 mph "comfortable" top speed, especially since I have the 15 footer as my main boat. I plan to find an 8 or 9.9 hp to use on the lakes with the 12 footer eventually, but there's really no hurry.
After experimenting with the 12 footer, I put the Johnson back on the 15 footer and the next week, took it out on the lake. When I opened it up to full throttle, something seemed different. It seemed...faster. A check of the GPS had confirmed it...I was now going 20 mph. Of course, I was happy, but how did this happen?
Remember when I adjusted the trim out, trying to get the hull of the 12 footer out of the water? Well, I never put it back...
Trim and Height
Trim is the angle of the boat's motor in relation to the hull. Trimming the motor in lowers the bow, trimming it out raises it. Generally speaking, raising the bow gets more of the boat out of the water, resulting in more speed. Of course, if you go too far, then the boat will plow with the front way too high. Like anything, you can have too much of a good thing. I had messed with the trim before, but never with this prop.
When I put the motor back on the 15 footer, I was now running two notches out on my trim, which made an incredible difference. The boat starts accelerating and it seems like it will keep going faster and faster. Some people prefer "hole shot"...trading top speed for acceleration. Since I spend more time running than I do accelerating, I'd rather have the top speed.
Motor height also makes a difference. Finding the right driveshaft length to match your boat is important, and if there's a mismatch, the engine can sit too low in the water, causing excess drag, or it won't reach deep enough into the water, causing prop ventilation, cooling issues, and other problems. A jack plate can correct for a driveshaft that is too long, but may bring its own set of problems.
All of this illustrates how much each of the factors depend on one another, and also illustrates how much you have to be a tinkerer to get the optimal setup from your engine.
Sometimes people see my minimal setup on my boat and tell me, "You need to add a casting deck to that! You need to permanently mount your swivel seats!" Or some other such suggestion to improve my boat to suit their needs. There's a reason I don't do that...
Weight
Another thing that will speed up your boat is to get rid of anything unnecessary that you're carrying with you. I used to carry a bunch of extra stuff that I found I never used...a whole milk crate full of "fishing equipment" most of which never got touched. A set of scales, three marker buoys that I never used, extra fishing reels, etc. Granted, it is better to have and not need instead of need and not have, but if you're selective with your equipment, there's no need to weigh your boat down with unnecessary gear.
No chance of rain? Leave the extra rain gear home. Plan on staying in motion most of the time? No need to take the anchor. Staying near the launch and using your trolling motor for the entire trip? Leave the kicker at home. Only fishing for bass? Don't bring the box with the muskie lures.
Lithium batteries are almost always lighter than lead acid, and these days, not much more expensive. Further, a lead-acid's capacity-to-weight ratio is not even in the same ballpark as a lithium.
If you're only going a short distance, carrying 3 gallons of gas is much lighter than carrying 6. If you're running ethanol fuel, you probably don't need to keep more than 3 gallons on hand anyway...
And probably the hardest payload of all...your own gut. As a big boy, I would see videos of boat after boat being propelled along on 6-8 hp and marvel at the fact that they could go so fast...then the dude turns the camera on himself and he's 98 pounds soaking wet, and that would prompt me to say to myself, "Maybe I could stand to skip a meal." It's not a fun thing to think about, but one that absolutely makes a difference.
Spend the time deciding what you will need (and what you will not need) and adjust accordingly. Before you know it, you'll have saved a significant amount of weight, because all of the individual choices you make add up.
Don't discount weight distribution as well. Even small movements front to back can make a big difference. With the aforementioned 7 hp China motor, moving my weight to the center (by rigging up a Rube Goldberg level steering/throttle/kill switch device) increased my speed by 2 mph, and I actually saw 10 mph a couple of times out of that setup.
Ironically, some of the same people who buy a small 14' jon boat and build casting decks out of 2x4's and 3/4" plywood covered in foam will then complain that they can only get 12 mph out of their 9.9 hp motor. Casting decks, consoles, permanently mounted swivel seats, etc, are nice, but in the end, they do cost a significant amount of weight. For some, it's a worthwhile trade-off, but for me, I like things to be simple, modular, and lightweight. I like things to be able to be moved from boat to boat. I also like for this boat to be as lightweight as possible for use on shallow rivers. All of that precludes heavy, permanent installations.
From the time I first tried the Johnson 9.9/1542 jon boat configuration, the top speed was somewhere around 15 mph. Through this series of tweaks, I have gained about 30% more speed than that setup. On almost every boat, the first trip is a starting point and you are nowhere near your optimal configuration. So, there you have it. Start by making the free adjustments you can do today and see if they make a difference. And don't forget to revisit often. You may find that changing one thing leads to other changes as well. In the end, you may find no need to trade up to a bigger motor in order to gain a significant amount of speed.
And probably the hardest payload of all...your own gut. As a big boy, I would see videos of boat after boat being propelled along on 6-8 hp and marvel at the fact that they could go so fast...then the dude turns the camera on himself and he's 98 pounds soaking wet, and that would prompt me to say to myself, "Maybe I could stand to skip a meal." It's not a fun thing to think about, but one that absolutely makes a difference.
Spend the time deciding what you will need (and what you will not need) and adjust accordingly. Before you know it, you'll have saved a significant amount of weight, because all of the individual choices you make add up.
Don't discount weight distribution as well. Even small movements front to back can make a big difference. With the aforementioned 7 hp China motor, moving my weight to the center (by rigging up a Rube Goldberg level steering/throttle/kill switch device) increased my speed by 2 mph, and I actually saw 10 mph a couple of times out of that setup.
Ironically, some of the same people who buy a small 14' jon boat and build casting decks out of 2x4's and 3/4" plywood covered in foam will then complain that they can only get 12 mph out of their 9.9 hp motor. Casting decks, consoles, permanently mounted swivel seats, etc, are nice, but in the end, they do cost a significant amount of weight. For some, it's a worthwhile trade-off, but for me, I like things to be simple, modular, and lightweight. I like things to be able to be moved from boat to boat. I also like for this boat to be as lightweight as possible for use on shallow rivers. All of that precludes heavy, permanent installations.
Buying a New Motor
In the end, you can't cheat physics. If you have a top speed in mind, you need to compare that to see what other users are getting out of similar setups. If everyone you know is getting 18-20 mph out of a 15 horsepower on a 14 foot boat, and you're only getting 12 mph, the problem is likely NOT your motor. Conversely, if your 14 foot boat is cruising at 12 mph on 6 hp, you've pretty much maxed that out and the only answer is to upgrade. But, upgrading your motor should never be the first solution to this problem...you need to address your setup before blindly throwing more power at a bad configuration.
The results
From the time I first tried the Johnson 9.9/1542 jon boat configuration, the top speed was somewhere around 15 mph. Through this series of tweaks, I have gained about 30% more speed than that setup. On almost every boat, the first trip is a starting point and you are nowhere near your optimal configuration. So, there you have it. Start by making the free adjustments you can do today and see if they make a difference. And don't forget to revisit often. You may find that changing one thing leads to other changes as well. In the end, you may find no need to trade up to a bigger motor in order to gain a significant amount of speed.
0 $type={blogger} :
Post a Comment