How fast should I go

I have a 56 Alumacraft Open C(15 footer), and A '62 Evinrude 28hp Speeditwin. Figuring in my weight and all my gear is around 400lbs. How fast can I realistically expect it to go?

my guess is 25-30 mph..

Well you and gear 400lbs, boat 300-400lbs and motor 100-120lbs, total 800-900lbs so I would guess 25mph would be the best case scenario. That 62' 28hp motor would be lucky to put out 25hp at the prop.

I have a 1652 with a 20 hp and with me and all my stuff I run around 23-24 mph at WOT the best I have done is 25 1/2 mph these figures come from the gps on my phone.

Wow, you guys are getting great results.
I used to have a 14ft lund, 2 guys, gas, trolling motor, battery, 2 anchors, fishing gear, etc., 15 hp mariner, top speed was 13 mph.
Now I have a 16.5 ft fisher sv2 with a 1988 48hp johnson, 2 batterys, gas, 2 guys, trolling motor, 2 anchors, fishing gear, etc., top speed is 29.1 mph.
I guess losing weight is a good idea.
Tim

I have a '82 Grumman Sportsman 4.6 (15' (Side console, full deck))with a 35hp full gear including trolling motor, batteries and a cooler full of barley pop. A very large me so I count that as two people and my wife. We do about 26mph per GPS at WOT with an 11" pitch. When I go it alone with nothing other than a small bait cooler and my tackle box I switch over to a 13" pitch and do about 34mph as per GPS.

15 ft john boat here with a 25hp souped up to 35 hp, and I get 32mph with the wind at my back...

As always tight lines, cold beer, and Go Gators!

my build...https://www.tinboats.net/forum/viewtopic.php?f=3&t=25183

I get about 20-25 mph (unofficially) in a '59 14', semi-V tinny with a '66 20 hp Johnson with a light load, and I would think that you could expect anything in the 25-30 mph range. Bare in mind that on vintage model outboards the hp was rated differently (at the drive shaft rather than the propshaft like modern motors) as a result, vintage motors tend to have about 5 hp less than there modern counterparts. So my '66 20hp is really more like a modern 15hp. However, just as important as raw horsepower is proper engine trim/tilt, height and prop. For best performance and decrease drag, you want the anti-vent plate found just above the prop to be level, or 1"-2" above the keel (bottom) of the boat. The plate should just barely break the surface of the water when on plane. Also, vintage OMC motors had sort of an odd leg length of about 18", which put them in between a modern 15" short shaft and a modern 20" long shaft. As a result, they often require a jackplate to raise the motor to the optimum height. Racers used to use shims as small as 1/4" to squeeze the most out of their motors. I didn't go quite that crazy, but I did clamp my motor as high up on the transom as I safely could. It raised the motor a couple inches and greatly increase my performance, particularly on the top end. I could buy/build a jackplate if I really wanted, but I'm pretty happy with it as is.

Thanks for all you input guys. That is a little faster than I was expecting. I have her just about ready to go and hopefully I can post a GPS confirmed speed sometime in the next 2 weeks.

I snagged the wife's GPS unit the other day so I could test this out. I have a 79 15hp Evinrude, and I got just over 25 mph on the Garmin. I had a trolling motor, battery, 2 anchors, 2 tackle boxes, small cooler, and me at 200lbs. I'm pretty happy. I'm assuming that in calm water I can get around 27 mph. I was getting a little bit of air with the chop on the lake, and though I like having PFD's I prefer not using them.

The real test is to have another guy sit up front, but I'm pretty happy about the results.

You will find that most boats will actually go fastest when there is a little chop on the water. Flat calm, glass like conditions will usually cause more drag on a boat. A small ripple on the water is actually perfect for optimum speed. This can be verified with a tach and GPS. I run 50-100 rpm more and about 1 mph faster with a small chop or ripple.

just got my boat back from having the 1989 johnson 25hp engine fixed....took it to the lake and ran 39.6 according to gps....my boat is a 2008 tracker grizzly 1448, trolling motor, 2 batterys, 3 gallons of gas, fishing gear and my 200 lb but.....i was pretty amazed at how fast this lil boat went.....didn't believe the gps on my fish finder so double checked on my phone and it was **** near identical readings.....the wind was blowing about 15 mph so there was some chop on the water......needless to say i was pretty happy! also this was the first time i took this boat out with that motor on it.....boat is brand new and the motor came from my old alumacraft bandit 17 footer with full wooden decks and loaded to the gills. and the motor pushed about 31mph...........awesome little motor it is!

I am sorry but I am not buying 39.6mph with a 25hp johnson unless it is on a hydroplane with a different gear ratio turning a racing prop.

In order for you to hit 39.6 mph with your 89' 25 that has a 2.15:1 gear ratio you would have to turn a 15 pitch prop at 6100 rpm with ZERO prop slip! Not even theoretically possible, I'm sorry your GPS must not be correct.

So what pitch prop are you running and what sort of RPM are you turning. More realistic numbers would be 29-32 tops with that engine and gear ratio. Unless like mentioned above you have it on a 100lb hydroplane

don't know what size prop it is but two differant gps units said the same thing....

You may want to find out what prop you have and what the RPM's you are turning. This is important to the longevity and health of your engine. The 89' 25hp is only supposed to run at 5000-5500 rpm.

Average prop slip would be 7-12% and at 5500 rpm on say a 15 pitch (which I doubt is on your motor, prob 13 or an 11) at your gear ratio of 2.15 would put you at 32-33.8 mph. And the 33.8mph with a 7% slip at 5500rpm with a 15 pitch would be awesome numbers and are rarely seen unless you have a very good prop and a very light setup.

But I doubt your 25hp can turn a 15 pitch at 5500rpm. And hypothetically speaking to get an 11 pitch to hit 39.6mph with your gear ratio you would have to get your RPM to 8200 with ZERO slip. And zero slip is not possible. A 13 pitch would be 7000 with zero slip. So you can see that it really is not possible to hit those numbers with your engine.

I can turn a 14 pitch SS prop at 5740 with my 88' 30hp and a light load in my 14' tin. Total weight around 800-850lbs, my prop slip is 13-14% and I hit right at 31mph which is fast in a little tin. Fast enough to make your kidneys bleed in rough water lol......

djchris said:

just got my boat back from having the 1989 johnson 25hp engine fixed....took it to the lake and ran 39.6 according to gps....my boat is a 2008 tracker grizzly 1448, trolling motor, 2 batterys, 3 gallons of gas, fishing gear and my 200 lb but.....i was pretty amazed at how fast this lil boat went.....didn't believe the gps on my fish finder so double checked on my phone and it was **** near identical readings.....the wind was blowing about 15 mph so there was some chop on the water......needless to say i was pretty happy! also this was the first time i took this boat out with that motor on it.....boat is brand new and the motor came from my old alumacraft bandit 17 footer with full wooden decks and loaded to the gills. and the motor pushed about 31mph...........awesome little motor it is!

Click to expand...

Would a 15MPH tail wind make his numbers possible? Could be an explanation.

djchris said:

don't know what size prop it is but two differant gps units said the same thing....

Click to expand...

39.6 out of a 25HP on a 1448 grizzly does sound high. Was your GPS set to km/h? 39.6 km/h is equal to 24.6 MPH, which seems more likely.

Bigkat650 said:

djchris said:

just got my boat back from having the 1989 johnson 25hp engine fixed....took it to the lake and ran 39.6 according to gps....my boat is a 2008 tracker grizzly 1448, trolling motor, 2 batterys, 3 gallons of gas, fishing gear and my 200 lb but.....i was pretty amazed at how fast this lil boat went.....didn't believe the gps on my fish finder so double checked on my phone and it was **** near identical readings.....the wind was blowing about 15 mph so there was some chop on the water......needless to say i was pretty happy! also this was the first time i took this boat out with that motor on it.....boat is brand new and the motor came from my old alumacraft bandit 17 footer with full wooden decks and loaded to the gills. and the motor pushed about 31mph...........awesome little motor it is!

Click to expand...

Would a 15MPH tail wind make his numbers possible? Could be an explanation.

Click to expand...

A 35mph tail wind would not even cause numbers like this. It at some point it cancels out when you reach the speed of the wind. Now a 70mph tail wind, could be possible? :shock:

Having GPS on km/h sounds much more reasonable as Ictlarus stated.

1448 MV with 2009 Yamaha 4stroke 25hp (bought new in 2011) - With me (210lbs), 2 X 20lb anchors, drift chain (about 8lbs), 3 batteries, trolling motor, deck, tackle and rods, 3 seats (2 are the oversized seats), empty bait tank (11gallon about 25lbs), fishing bow and arrows, 6gal of gas......26.5mph, 27 will a little push from wind/current.

Fill the bait tank up with water and add another person about my size.....22-23mph

gps was not set to km/h.....im not doubting what you guys are saying but i am going off of what 2 differant gps said.....it was scary fast. i will re-check tomorrow when i get my boat back from the mechanic again...(whole other issue) anyways it may have been a screwy reading but 2 differant gps read the same numbers.....so who knows.