Boat Speed Problems?

hi all,

I have 5 hours of break in time on my new 2016 alumacraft competitor 175 sport. This boat has a Suzuki DF140 and a Suzuki 9.9 kicker and a 24 volt trolling motor (so two batteries), and I feel like the boat is not moving as fast as it should be. Now im far from an expert on boats/motors/boat navigation so I am almost expecting some sort of user error here but I want to ask for feedback on what might be going wrong. The top speed ive been able to get on this boat with minimal chop conditions is around 38mph with my 110 lb wife in the boat and some fishing gear. From other forums and reports ive heard that this setup should run closer to 42-45 mph. After talking with a friend, on this last trip I trimmed the motor up a bit and was able to increase my previous high of 33 or so to 38 so that helped a lot. I run non-oxy gas. The trolling motor batteries are in the bow of the boat and so is some of the fishing gear so I feel that weight distribution shouldn’t be an issue…..

Thoughts?

More info please- -WOT rpm and redline for motor, prop whether alum or ss, dia/pitch, 3 blade vs 4 blade. Total loaded hull weight. Air/water temps are also determining factors. Too many factors involved to be able to dial in the perfect set-up right off the showroom. Time, miles and money will eventually lead you to what you feel is optimum performance for your new rig. My old barge won’t even come close to factory specs, but my big fanny, half the toys known to mankind, a prop that is special made to back troll with all contribute to its’ shortcomings. I always figure that there’s not many fish caught at speeds over 5 mph anyway jerr

What pitch prop do you have? My 17 ft Tyee with 115 merc 4 stroke and 16 pitch prop hits 40 with me and my 6 yr old. I do not have a kicker but when I get a few more people in fishing with me the 38 mph mark is regular.

I think you should keep increasing the trim while running wide open. Pay attention to the RPM gauge on the boat. The ideal rpms should be somewhere between 5800-6000. Once at those rpms check speed.
I was water testing a boat yesterday on the river and noticed 10mph difference and 1000 rpms difference between zero trim and max trim.
As you become more familiar with the how the boat runs, you will begin to get a feel for the boat and how it runs at different speeds.

Calvin Svihel wrote:

I think you should keep increasing the trim while running wide open. Pay attention to the RPM gauge on the boat. The ideal rpms should be somewhere between 5800-6000. Once at those rpms check speed.
I was water testing a boat yesterday on the river and noticed 10mph difference and 1000 rpms difference between zero trim and max trim.
As you become more familiar with the how the boat runs, you will begin to get a feel for the boat and how it runs at different speeds.

This^^^.

Also, your trim stop pin may be set too low so that you have to trim up excessively when under way. Ideally, you want your trim stop pin set at the “best hole shot” location and no lower to minimize the upward trim travel you have to apply to get to best trim for running. My guess is that from the dealer your pin is set at the lowest setting. The only way to determine this is by trial.

Grouse

I think with only 5 hours on the boat it will only get better. When I broke in my motor 5 years ago I never did any lengthy high speed runs with that little time on it. I believe the owners manual for my motor (Suzuki 150) said to keep it below a certain RPM level, but that was 5 years ago so I don’t remember.
At any rate, trimming the motor will make a huge difference. Start with the motor trimmed all the way down and go full throttle watching the peak RPM. It should hit the peak RPM and pretty much hold steady. Compare that # to what the operating peak RPM is from your manual. If the number gets too high, you need to go up in pitch, too low, go down. The higher the pitch you should get more top speed, but it will sacrifice low end performance so pick your poison there.
Once you are on plane, trim the motor up until it begins to catwalk. You should actually feel the boat lift off the water almost like you are in a plane.
Have your lovely wife drive your boat while on plane and then make your way to the back to check motor height. The cavitation plate (fins) on the motor should not be much below the surface of the water or its killing your top end. At least in my experience.
If you do not have a stainless prop on that motor I would suggest it. I know most 140’s do not come with one, but IMO it should be used on everything over 115. There is a lot of flex in aluminum props.
All in all, 38 is pretty respectable. I would bet you will get another MPH or 2 once its fully broken in without changing anything.
I find that I don’t even run my motor wide open anyway. I get about 45 MPH for my boat loaded up. 185 Tournament Sport with 150HP Suzuki. I had a taller prop on it when I first bought it and I was hitting over 50, but I didn’t like the trolling speed or holeshot so I dropped down.

thanks all. Ill have to gather more info for you guys as I don’t have the answer to some of the questions.

“All in all, 38 is pretty respectable.”

I agree, and I don’t really have much of a desire to go faster my main concern really is that I want to make sure nothing is wrong with the motor in case I need to contact the dealer. If the motor is fine I am more than comfortable going 38mph for top speed I just want to make sure there isn’t something wrong with the motor, but as I can tell by the responses, there is a whole lot that factors into a boats performance

crappie55369 wrote:

thanks all. Ill have to gather more info for you guys as I don’t have the answer to some of the questions.

Here is a link to a performance test with a 140 and a 175 Trophy. I know its not exactly your boat, but it should be comparable.
In this test they use a 14×22 Stainless prop. I think that makes a big difference IMO.
Also pay attention to the mounting location of the motor. Which hole its in and compare that to yours.

http://www.suzukimarine.com/~/media/Marine/BoatBuilders/TestResults/A/Alumacraft/Alumacraft%20Trophy%20175%20DF140.ashx

Need prop info, pitch, number of blades, stainless steel, aluminum. Which holes the motor is mounted in. Max rpm you are getting at full throttle. Full windshield or bubbles????????? 38mph sounds like it is in the ballpark so it shouldn’t take a whole lot more tweaking to get it right.

I agree with the others. Prop pitch, blade numbers and material along with max rpms will help a lot. A general rule of thumb is once you’re on plane, trim up until it does one of two things
1. Blows out, if this happens note where on your trim gague it happens, so you can use that as your max trim reminder
2. You over-rev (if this happens, you can probably get by with a higher pitch prop).

Agree with everything people have said except one thing. When trimmed out and on plane your cavitation plate should just be out of the water.

Jonesy wrote:

Agree with everything people have said except one thing. When trimmed out and on plane your cavitation plate should just be out of the water.

X2. Anti Ventilation plate is useful during acceleration but should be out of the water slightly at WOT. SS props work best for high HP motors. I had a Trophy 175 w/ 115 Etec that did 40 mph GPS with an aluminum prop at optimal rpm 5750 in 2007. I had a lighter kicker than you but a heavier boat. Engine was at second highest position. Dealer set it at a lower position and many of them do. learn to trim your motor up until it starts to let go and then trim down enough to just hook back up. good luck.

I have a 2015 175 competitor sport with a 115 merc 4 stroke and a 8hp kicker. With 2 guys, full live wells, half tank of gas I am running 41 to 42 in calm conditions. This is with a 17 pitch aluminum prop.

My old naviagator 175 sport had the motor mounted to low from the dealer. Raised it up two holes to where it belonged and picked up 2 mph and had better handling. Changing to a stainless prop added another couple mph, and getting the pitch right added one more. Top-end with a 150 e-tec was right around 51 mph. I would expect you should see a higher top-end than 38.

It amazes me how many dealers have no idea what they are doing when they setup their boats. I bought a used boat this spring and right away I noticed the boat would only turn 5200 rpm’s at WOT. Should be turning 5600-5900. It was also running at 52 mph. The dealer had a 25 pitch prop. Seemed way too much. Re propped to a 21 pitch but larger diameter and ran the same 5200 and 52 mph. I called and talked to the manufacturer and he asked what level the motor was set at. I said it was one up from the bottom. He said that with a 200hp motor it should be set on the top hole. I moved the motor up and ran it today. Now I am hitting 5800 RPM’S and 59 mph. Just another reason to buy a boat from a dealer that knows what they are doing. I know that the Skeeter boat center and rapid Marine both know what they are doing. It seems the majority of others in the area don’t have a clue.