19 pitch prop on 50hp evinrude update!

[michaelj1978]

Well the prop was a success. I took it out saturday night for a run at the lake. First with the 15pitch prop, then the 19.<br /><br />Boat is a Fisher Marine 18 foot flat bottom aluminum. Interior is fully decked out(storage/seating) and we had myself (200lb) my friend (230lb) and all of our gear, including a big cooler full of beer. Also there are 3 batteries and a topped off 6 and 2 gallon tank to give you an idea of the weight of the boat. <br /><br />I also hooked up the GPS (eagle 320) with the hotmaps which worked great. If you don't have GPS and a map like this get one!<br /><br />With the 15 pitch I was only able to hit 19.3mph without the motor starting to over rev. Took off the prop and threw on the 19 pitch and we topped out at 26.9mph. I don't think this boat's ever been that fast! Felt like a whole new boat. Motor ran great and sounded like a motor should. We had no problem getting the boat to plane and once up, tilted the trim back and skimmed the rear 1/4 across the water.<br /><br />Water temps were also in the low 50's and we had a little wind. I think on a warmer day with less wind, less weight in the boat, I might be able to hit 29-30mph.

 

[angus63]

Re: 19 pitch prop on 50hp evinrude update!

The most important part of the equation is what rpms were you turning at WOT??????

 

[michaelj1978]

Re: 19 pitch prop on 50hp evinrude update!

6000

 

[angus63]

Re: 19 pitch prop on 50hp evinrude update!

Difficult to achieve your numbers with a 50 HP turnin' a 19" pitch on a loaded 18' boat and a WOT of 6000 rpm. Something tells me your rpm's are off by about 1000 (more likely your turning 4600-4800 rpm). I would verify tach before settling on that prop. 19" seems real steep for your setup.

 

[ob15]

Re: 19 pitch prop on 50hp evinrude update!

I agree with angus63. I'd be interested to see how much the rig weighs. I have a 15' deep vee (15 degrees) with a 50hp & 17" prop. I need a 19" to drop rpms to an acceptable number. When I first mounted the motor (with the 17") I was amazed it shot above 5900 real quick & good thing I caught it and pulled the throttle back (although the rev limiter would have kicked in). BTW, I'm using a tiny tach so I know it accurate.

 

[walleyehed]

Re: 19 pitch prop on 50hp evinrude update!

Your tach is INCORRECT or you still have MASSIVE ventilation.<br />6000RPM on that engine with a 19 pitch prop equates to approx 48.6MPH..<br />Your 26.9MPH with a 19 pitch equates to right at 4000RPM, just a tad less.<br />You have a Major problem you need to figure out now before you ruin your engine.<br />You're talking my specialty here, and I'm tellin' ya you have a problem.

 

[steviecops]

Re: 19 pitch prop on 50hp evinrude update!

My boat is comparable to yours, so you might be interested in this.<br /><br />I run a 17ft tri hull boat that weighs around 1000lb, with a Johnson 55 on the back. With 2 adults, fishing gear, fuel, batteries and auxillary motor, I could only get about 5200 rpm with a 17 pitch prop. I changed over to a 15 pitch and now I get 5800 and an extra 2 knots. Gets up on the plane quicker too.<br /><br />With a 19 pitch prop on my boat, I doubt it would get on the plane with a load up.

 

[ledgefinder]

Re: 19 pitch prop on 50hp evinrude update!

Note the 50 has a VERY low ratio gearbox. 2.66/1 if I remember right, as opposed to 2/1 for the V4s. <br /><br />What year is the 50? I'd believe a 1986+ 50 would do it, given it's a flat-bottom aluminum hull.

 

[Dhadley]

Re: 19 pitch prop on 50hp evinrude update!

I'll stick by what I said in the other post. And what Walleyehed said. Somethings wrong. The gear ratio is, I believe, 2.42 so that figures out at 40% slip if the tach is accurate. Doesnt add up.

 

[michaelj1978]

Re: 19 pitch prop on 50hp evinrude update!

It's a 1995