Prop pitch question on Johnson 50HP on a LOWE 1648 aluminum boat

[bigd5656]

I recently ruined my prop on my Johnson 50hp engine. I took the numbers off the old prop and ordered a new 11 3/4 x 17 replacement. I took it out this weekend and could not plane off and had no power. Apparently I'm going to need to reduce pitch size but don't have a tach. I was thinking of going down to a 12 or 13 pitch was was wondering if anyone had a similar setup that could recommend a pitch starting place? My engine is a Johnson 50HP on a LOWE 1648 aluminum boat. Any help would be appreciated.

 

[steelespike]

What year boat and motor? Is it a bare bones tiller setup?What numbers are on the old prop? Is it a 17" pitch?
If it's a bare bones it should be near flying with a 17.

 

[bigd5656]

It was doing pretty good with the old prop. The numbers on the old prop are 11 3/4 x 17. I used these to purchase the new Hustler prop. The motor is a 1990 50hp 2 cylinder. The boat is a 1998 Lowe 1648. This weekend was my first time out with the new prop and the engine struggled to push the boat.

 

[bigd5656]

I forgot to mention that it's got a steering wheel rather than a tiller setup.

 

[steelespike]

In 98 there are 16 models based on the 1648 model number.Weights are all very close at about 285 but for 2 that
are L1648 MPT at 370 lbs These all seem to be rated for 25 hp.
My 18 ft Crestliner bare utility is 335 lb 1,000 lbs all up weight with a 88 50hp tiller Evinrude. running a 19" prop.
It is a bear, instant leaping on plane speeds close to scary. Still strong hole shot with 1000 lbs load in the boat.
If your boat struggles with a 17" prop you probably have a motor issue possibly the setup.
Usually the Hiustler props it is suggested to decrease pitch 1" but I feel your boat with a light load should do well unless it was struggling with the old prop.

 

[lmuss53]

You don't mention how the old prop got damaged, the damage didn't go further than you think did it?

My older 55 with a 13p on it is just right for my 20 foot pontoon, the 17 should be popping up out of the water and running way wound out on your 16 foot boat.

 

[bigd5656]

I got in some shallow water and hit some rocks which destroyed my old prop. I believe my problem is unrelated to prop pitch and likely related to spark. I think I may have been running on one cylinder. I'll check spark over the next few days to confirm.

 

[steelespike]

You wouldn't be a first with throttle linkage problem from contact with rocks.