Bass Boat Prop Selection

[RMG75]

Hello all,

I've seen a lot of good info on here from knowledgeable people, so I thought I would give my delima and hopefully get some good feedback.

I have a 1989 Bass Tracker 1600TF fiberglass bass boat that I just put a 115HP Evinrude 2 stroke on. The motor came off of a bigger bay cruiser boat (for lack of a better term), and the prop is size is nowhere near what I need. The prop size is a 15.5X13 pitch. Lake testing the boat a few days ago I found the bow rise at take off was wayyy extreme, with a top speed of only 33mph and it porpoises like crazy, even trimmed all the way down. Two people were in it.

After using a prop selection chart online it says the prop I need is either a 13.25x19 or 13.25x 21. I know a SS prop is the way to go for best performance, but I'm thinking of just getting an aluminum prop for now. Starting with an alum prop should at least give me an overall average performance.

So I guess my question is.. does that prop size should like a good starting point? Or does that should way off? Any feedback would help.

 

[Sea Rider]

Welcome to Iboats,

Current prop is your starter prop, post wot rpm achieved on flat calm no wind water cond as loaded. Compare reading to factory min-max wot rpm range. Will know how far off from at least middle to max wot rpm range that OB runs. From there can go for a prop maximization. OB should be trimmed for boat to run parellel to water level once on plane, usually trimmed at 90?. OB/transom height is key for best water performance.

Any other prop you choose must be water tested as currently loaded, this is not rocket science...

Happy Boating

 

[RMG75]

W.O.T. operating range is rated @ 5250-5750 rpm.
Current prop WOT is at 5400 rpm.

The porpoising I'm hoping can be solved with a different prop. I'm hoping it is falling off plane due to that. I had the motor mounted by a marine shop so it's mounted at the right height. It's not rocket science I understand but with the research I've done it's safe to say that when choosing a prop there's no silver bullet carved in stone fix all. There's a lot of trial and error. A 19 or 21 pitch seems like a starting point.

 

[Sea Rider]

I've seen lots of "Pofessional OB Installations" done by OB delaers as well by three shade mechanics that weren't so once combo was running on water at speed. Going for the AV plate even with rear hull/keel does not always dials sweet OB/transom height when doing a dry installation.

Need to water test combo to fine tune OB/Transom height if wanting boating perfection, aside from a prop maximization if needed. Was 5400 wot rpm achieved with current prop while lightly, medium or heavily loaded ?

Happy Boating

 

[RMG75]

I get what you're saying. I'm hoping it doesn't turn into too much of a pain in the butt.

I'd say it was medium-heavy loaded. Had no tackle, anchors etc in the boat. Had 2 guys,two batteries, 22-25 gal of fuel and some misc lightweight things. I weigh 180 and my friend that was with me weighs 220ish probably.

The place that installed the motor is going to put a 14.3X21 on for me to take out and try. So I guess I'll start there and hope for the best.

Thanks again, I appreciate your input.

 

[Sea Rider]

For the record, report back if newer prop solved the porpoising problem. If not, could be a bad OB/Transom height match that needs to be corrected. It's done once, once dialed can go boating happily for ever.

Happy Boating

 

[RMG75]

Will do. I expect to give it a go Friday or Saturday.

 

[RMG75]

Took it out today with the 14.3X21. Same weight in the boat. Same 2 people. It really helped. The bow rise at take off wasn't near as extreme and had plenty of trim to play with without porpoising at top speed. Top speed was 47mph, water was choppy.

When I get around 30mph the boat falls off plane and starts to porpoise. I'm thinking a hydrofoil may help with that. And as luck would have it, my tachometer wasn't working so don't know what the rpm's were. Gotta get that fixed before I go out so I can see if I'm in the range I need to be.

 

[Sea Rider]

Ideal is to make water trials at early morning when water is flat and non windy. Testing can dial best OB/Transom height under those conditions. If installing a doel fin combo, AV plate must ride parallel to water level, if not doesl will achieve water drag and slow combo a bit.

If say you leave trim set at 90?, distribute deck weight evenly, go full throttle on flat calm no wind water, how's hole shot, does combo porpoises same ?

Happy Boating

 

[walleyehed]

Took it out today with the 14.3X21. Same weight in the boat. Same 2 people. It really helped. The bow rise at take off wasn't near as extreme and had plenty of trim to play with without porpoising at top speed. Top speed was 47mph, water was choppy.

When I get around 30mph the boat falls off plane and starts to porpoise. I'm thinking a hydrofoil may help with that. And as luck would have it, my tachometer wasn't working so don't know what the rpm's were. Gotta get that fixed before I go out so I can see if I'm in the range I need to be.

I can help you with this but the 47mph means absolutely nothing without an accurate rpm. porpoising at 30mph is normal for an incorrect blade design. Lots of questions here.. Pad bottom? Trim stop hole used? Mounting height?? lots of things to look at on that type of hull. Whale-tail on a Bassboat is a band-aide for other problems.