1989 285 pro PTP question.

[jt1009]

I have a new to me 1989 285 pro with a mercury 150 xr4 with a 14.25x21 rapture stainless prop. Also has a 6" detwiller manual jackplate. I measured the ptp before making any changes and was at 4.75". From what i read the industry standard to start with is 3.5" and is what i set it to, when testing it seems to plane about the same to maybe a little improvement. Now when i try to reach wot it seems to be slipping alot. I could only get to 48mph at 5800rpm which is a little high i know for this motor. My question is if i went with a different prop say a tempest plus with same pitch would the results be the same meaning just wanting to have a lower ptp or would this change. I also have not tested full wot at original settings but when i did drive it i could get to 51 with more trim left and not sure of the rpm at that time as i was having a carb float issue in the beginning. In addition with original settings i could actually feel the motor pulling when accelerating where higher ptp was basically flat. Any advice or insight is greatly appreciated TIA.

[Coach185]

Our 93 Javelin 379 (18') with a Johnson FastStrike 150 run a Raker II 24P. PtP is set at 3 1/2" and has a older 6" jackplate. Jumps up on plane in 2 seconds.
My 2003 Stratos 185 with a Yamaha 150 runs a Mercury Tempest Plus 25P. PtP is set at 3 1/2" and gets up on plane in 3 seconds. It has a Vance 6" jackplate. Both props have been worked by Mark Croxton in Indiana and have some cup added to the blades.
Are you starting out with your motor trimmed all the way down and then slowly trimming up?
Can you tell us how you measured your PtP.
The title of your post indicates a PtP question, but your main question is about your Prop. I would suggest asking your prop question in the Prop section of the forum.

Welcome to the BBC

[jt1009]

For the ptp measurement i leveled the bottom of the boat at the rear and measured from the floor to bottom of boat, then leveled cavitation plate and measured from floor to center of the prop shaft and subtracted the 2 measurements. I measured in my storage unit figuring floor grade would not be a issue. From research i have read it just seems 4.75 is low and would i have same characteristics with a different prop. It is trimmed all the way in and does get on plane nicely, was just concerned with all the slip at wot at the 3.5 ptp setting or would a different prop allow me to run a higher ptp then the one i am running. I don't want to waste money on props if it just needs to have a lower ptp setting i guess. I have had pleasure boats in the past but this is my first bass boat and they are certainly different for me in a positive way.

[Coach185]

My Stratos 185 was set at 4.5 with no jack plate. Got up on plane in 5-7 seconds and had good top end speed of 60. Then reworked the 25P prop and gained a couple mph.
I would throw the question out in the props section as I would guess more pitch would help you out.
Your PtP procedure is spot on.

[BuzzB8]

The engine is too deep and once you begin to raise it you'll encounter more prop slip. I'm not a merc guy, so I'm making a guess here, 24 or 25 inch pitch prop, add a little more cup to the tips for bow lift, and raise the setback somewhere between 3 and 3.5 inches. That should get you a little more speed.

Find the prop and height that works the best for now. Once you're dialed in, contact the BBC prop guru (Mark) and let him b/b the prop. Then tweek your setup.

[jt1009]

Thanks guys, i have recently posted in the prop section as well.

[Les Young]

Our 93 Javelin 379 (18') with a Johnson FastStrike 150 run a Raker II 24P. PtP is set at 3 1/2" and has a older 6" jackplate. Jumps up on plane in 2 seconds.
My 2003 Stratos 185 with a Yamaha 150 runs a Mercury Tempest Plus 25P. PtP is set at 3 1/2" and gets up on plane in 3 seconds. It has a Vance 6" jackplate. Both props have been worked by Mark Croxton in Indiana and have some cup added to the blades.
Are you starting out with your motor trimmed all the way down and then slowly trimming up?
Can you tell us how you measured your PtP.
The title of your post indicates a PtP question, but your main question is about your Prop. I would suggest asking your prop question in the Prop section of the forum.

Welcome to the BBC

You're running a 25 tempest plus on a 150? The yamaha must have way different gear ratio then the merc. My buddys triton with a 200 optimax runs a 25. I've wanted to try a tempest plus on my 18 xl with 175 johnson & have a buddys 23 to try so may do that Friday night to see how it works, but i suspect it may be a little to small.

[Coach185]

Yes Les you are correct. The Yamaha V150TLRB has a 2-1 gear ratio and turns the 25P nicely. The Johnson FastStrike 150 has a 1.86 -1 and turns the 24P Raker II nicely.
If I understand correctly the Merc has a 1.83 - 1 .
My comments were meant as a comparison for him and hence my suggestion to post on the Props section.

Will the spline on my 25 fit your johnson? If it will, PM me

[Coach185]

Well Josh I would have thought someone in the Props section would have jumped in.
Our 93 Javelin 379 with the johnson faststrike 150 had slippage when I first started working on it. The prop was a out of the box Raker II. I sent the prop off to Mark Croxton in Indiana (Marks Performance Props) and he refurbished the prop and added some cup to the tips of the blades. Picked up some speed, but hole shot improved and slippage disappeared.
I would recommend you calling Mark and get his recommendations. He may suggest another prop or tell you he can refurbish and get your prop to perform to your specs.
Best of luck with your 285!

[jt1009]

Its ok, thanks for the recommendation.