[Dubhicks]

Need your help guys

I have an 2004 14' skiff that has an Evinrude 15 4 stroke that I picked up recently. Fires right up first pull and idles like a champ. The previous owner installed a solas 4 blade prop right before he sold it to me and never water tested it. Took the boat out with a friend and twisted all the way open I was lucky to make 7mph (GPS). My initial thought was that it was over propped for the weight. Keep in mind the vessel is rated for 4 people or 500 lbs. with us and a little equipment, we were right at 500. So I installed the old prop (9X11 I think) and installed a tiny tach to see where I stood.
Took the boat out this afternoon for some test running. Cranked it up and checked idle, was 625+-50 (didn't realize I had it on the wrong setting (180° instead of 360°)). Twisted it open to full throttle and got on plane ok, checked the tach and it wasn't going any higher than 2600rpm (again, wrong setting). So I doubled that in my head and I assume it was running around 5200ish.
Thing is, this thing doesn't scream like I thought it would at full throttle. It actually doesn't seem like it's struggling at all, I just can't crank it any further. Maxed out at 13 mph with just me! WTH!
When I got home I checked the emissions sticker and it is suppose to idle around 1000 rpm. With a quick setting change on the tiny tach, presto-1000 rpm.
I am only use to running 2 stokes and familiar with the way those things scream when at WOT. This is my first 4 stroke and I feel lost. I feel I should be getting way more than 13 mph with me in this small boat. I had an old jon boat with full decking and a wide beam with an 83 Johnson 15 2 stroke that would do close to 20 mph with me, my wife and kid.
Please help me get this figured out guys.
Thanks

 

[Brett]

What hull, hull weight?
Is the butterfly opening fully?
Prop pitch/diameter?

 

[Dubhicks]

The hull is an 04' sundance k14 skiff, open tiller.
The butterfly (when viewed from intake) goes completely horizontal
Prop-9"X11 pitch
If I had to guess, boat weighs between 3-400lbs.
Rated for 700lbs persons, motor, and gear.

I'm now wondering if the timing belt may have jumped a tooth at some point? Idles fantastic and drives out ok, just doesn't feel like it has any balls.

Model #E15R4SSE

Solas prop was 9.25"X9 pitch

Hope this helps

 

[Dubhicks]

Oh, and I've tried every trim position available (manual tilt) and the 13 mph was in the best setting, one up from the bottom. Also, cavitation plate sits 1/4-1-2" below the bottom of the transom.

 

[Brett]

Hull weight is killing your outboard.
K14 is a 500 lb hull from the spec sheet.
Minimum recommended hp is 25.
That's why you aren't getting any speed.

Load is total weight of hull, outboard, gear, fuel and passengers.

Horsepower to load ratios that I use:

1 hp for every 40 lbs of load will get you there. :-[



1 hp for every 30 lbs of load will get you there pretty quick.

1 hp for every 20 lbs of load and you'll be pullin' hang time. [smiley=carcrash.gif]

 

[Dubhicks]

But it also has a max hp rating of 30 Not sure if there is much more I can do. I always thought that the motor should be at or around 70% . With a 15 being 50%, I would think it should move better than jogging speed.
And, I thought the rule of thumb was 1 hp for every 50lbs, which would equal out about right for a 500lbs hull, 190lbs person, and 104 lbs motor. Keep in mind, this last test I ran bare bones with 2 gallons of gas.

But, if it's the best I can do, I can deal with it.
Thanks for your input.

PS Know anyone wanting to trade a 25 for a 15 lol

 

[Brett]

Quick way to find out if it's hull weight or engine problem.
Hang it on an aluminum 14 foot jon boat and see if you get the same results.
The K14 has a foam filled area under the cockpit sole, wonder if it's gotten wet.
That'd jack up your hull weight to where it'd affect speed also.

 

[Dubhicks]

I can lift the boat up off the bunks with the motor still attached, so I don't think I have water ingress in the foam. Don't have an aluminum boat to test. Those are great tips, I sure appreciate it.
If I'm getting the right rpm's, and the throttle is all the way open, then I have to assume that you are correct and the hull is too heavy for motor. Must be getting some serious slip