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Todd in NY

Selecting The Right Prop

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I bought my 1988 Crestliner Sabre a few years ago with a 1989 Evinrude 150. The prop was a 15x17. It was my opinion that the boat was sluggish to get on plan with a full load, and I ran this prop for 2 full seasons. So I researched some prop selector tools online and they recommended a 15.25x15, based on the weight of my fishing gear and people on board (heavy load). Both props are aluminum 3 blade. It seems that heavier loaded boats require a smaller pitch prop, such as a 15 pitch instead of the 17 pitch I started with.

 

Now I feel that my boat gets up on plane more smoothly, and my top speed is slightly faster at 34 and some change. That's close to 2 mph faster at 5200 rpm wot. I also think the motor is burning less fuel. I'll have to check my owners manual for my motor wot rpm range, but iirc 5200 rpm is in the ballpark.

 

Just wanted to pass this along because I had asked the question before, on which prop to choose, and I couldn't get a straight answer.

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Usually you go by your rated max RPMs for the engine ,what you are achieving with a normal load ,then go up or down in pitch based on that. Yes you will get better fuel economy , better speed and less wear on the engine if propped correctly. In your case you will also troll slower at the same rpms you were at before the new prop.

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I just recent spent this season trying to find the correct prop for my rig. I recently  completely had my 4.3l rebuilt and swapped my OMC drive to an Alpha 1 Gen 2 unit. with that said there was no prop with the new unit so i started with the old OMC prop that was on the old drive.  15x17 was my starting point. i recorded my speed and WOT rpm then went to that same site. I found the dry weigh of my boat and entered in all the information. I think the initial. recommendation was a 14x17 if i remember however it was not even close is wa at the MAX RPM of the engine recommended by the builder at WOT and on plain. OMC recommend the WOT should be at 4600 rpm. for every inch in pitch the rpm decreases about 150 rpm for every inch of diameter the rpms should decrease 500rpm. I found there are way too many factors to follow a chart. I suggest weighing the boat empty first  then add all your gear you normally would put  in on a trip add in the weight persons on board on a normal trip and tune the boat with that weight on at time of testing. You boat will perform different when your are alon than when 4 people are onboard. props are give and take, you cannot have a holeshote and ttop speed at the same time. In my case I started at a 14x17 and went all the way up to a 14x 21 and finally settled in at a 14x19. Turning Point recommended the 14x21 but it just didn't work the way i liked. I went with the 4 blade aluminium basically i wanted the 4 blade torque to have punch in the waves on the ocean however i didn't want to  give up a bunch of top end. I didnt even venture into SS props as i am know to tear up several per season. this summer alone i had 3 strikes on my blades that i never saw the submerged objects 2 I felt as i passed over them but the 3rd may have been a sea creature as the blade was trashed but no signs of impact wothe the normal hard object. I fish river where they are tidal waters and the amount of [email protected]#t floating is amazing. In the end i settled with a TP Hustler 4 blade 14x19 prop the plains quickly and i still can get 30 to 34mph top speed at 4600RPM WOT properly trimmed. BTW the prop calculator indicated a top speed of 45MPH LOL not even close!

 I hope this hepls

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Thanks for the feedback, dbitting!

 

The prop calculator is a good starting point, but there are far too many different factors to consider with each individual boat, which makes any prop calculator just a ballpark suggestion, as you pretty much stated above.

Edited by Todd in NY

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