do i have the wrong prop pitch??

[Jgothing]

hey guys, been a while since I have been on here, busy with life and all.. So ill cut right to the chase, i have an 1989 Bayliner Sunbridge 2455, 24 FT. replaced the motor over the winter, and took it out for a test run this past weekend, run great. hooked up the threw hull exhaust ports, turns heads when it starts, the motor is a GM 350, bored .030, comp cam, high rise intake, 600 cfm carb, and the out drive is alpha one. the prop on there is a stainless 3 blade, 15p, which is the pitch im guessing, i dont recall the exact numbers, but its 19***** 15p. so what my concern is, is how long the boat takes to plane out. almost embarrassing to have a nice sounding boat, and it cant get up , im usually and where from 2/3 to 3/4 throttle, and it takes a but to finally get up, and once its donse, its at 4500-4600 rpm, and runs about 30mph, so is there a different size prop i could try to get up faster, maybe have a faster top speed? i can rebuild motors all day, but im unfamiliar with the prop sizes, and what to look for, and what to compare with as far as prop size to engine size ratio. thanks for the help! im hoping i can look around and find some used ones maybe and see how they work over the next couple weeks, thanks again!

 

[dingbat]

Is this a new to you boat?

My boat has a great hole shot and it would take a while to get my boat out of the hole at 2/3 to 3/4 throttle. You need to dump the throttle, then back it off as you come up on plane.

No HP to prop ratio. The weight of the boat and hull type is a bigger contributor.

What is your WOT RPM and speed?

 

[Jgothing]

no its not new to me, i have owned it for 3 years this years, first year i had it, i put the motor back together, and it ran great from what i can remember, than shortly it stopped running good, no power, would not rev past 2500 rpm at WOT in drive, and would not get up, so all last year we just camped on it at the slip, but i wanted to fix it, and so i dropped a fresh motor in it, this past winter. i cannot for the life of me remember top rpm and speed from the original motor, but this weeked, my top speed was 32, and my max rpm was 4600-4700. ohhh ok, ive never just dumped the throttle maybe ill have to try that instead, i was going slow and taking it easy with the new motor and having people on board and what not. ill have to try it, full send. as far as the hull weight? i have no clue. ill have to toss is on a scale, on the trailer, then re weigh the trailer, and subtract the difference.

 

[QBhoy]

Hi. You may get a couple more mph out it but not much. Mid 30’s would be good going I’d say. Are you trimming the drive up at full throttle ? Trim tabs up and out the way at full throttle ? They can slow you down loads.
I also know from having a 2255 previously and being on a few 2455...that they are poorly designed in terms of weight distribution. Mainly in terms of the big fuel tank and all passengers being towards the rear of the boat. The difference in planing time with a full tank and a 1/4 full tank was huge on mine.

not sure if your gear ratio, but I know loads of guys that run either a big 16x16 black max prop or a normal 14x17 black max prop on similar boats with the 350 and alpha leg.

 

[dingbat]

no its not new to me, i have owned it for 3 years this years, first year i had it, i put the motor back together, and it ran great from what i can remember, than shortly it stopped running good, no power, would not rev past 2500 rpm at WOT in drive, and would not get up, so all last year we just camped on it at the slip, but i wanted to fix it, and so i dropped a fresh motor in it, this past winter. i cannot for the life of me remember top rpm and speed from the original motor, but this weeked, my top speed was 32, and my max rpm was 4600-4700. ohhh ok, ive never just dumped the throttle maybe ill have to try that instead, i was going slow and taking it easy with the new motor and having people on board and what not. ill have to try it, full send. as far as the hull weight? i have no clue. ill have to toss is on a scale, on the trailer, then re weigh the trailer, and subtract the difference.

Selecting a prop isn’t rocket science and you don’t need to know the weight if you have current performance as a reference point.

Typically you prop to achieve the mfg’s WOT rpm with your typical load on board. Need to be able to run the boat hard to get good numbers. Probably best left until your done with break in.

info you need:
What is your motors recommended WOT?
What WOT rpm and speed are you getting with your current (15 pitch) prop?

Unless your pumping out significantly more HP than before, probably not going to see much of a speed improvement.

I suspect in the end you’ll end up keeping your current prop. Your rpm and speed reconcile Pretty closely with the 15 pitch prop I’m running on my boat.

 

[jimmbo]

I suspect the Cam you picked for the motor is a grind that is not good in a Marine engine. The take forever to Accelerate but eventually getting near the WOT rpm range, is one symptom.

I hope the rest of your choices for Carb, Distributor, Starter are all Marine Certified.

 

[H20Rat]

bored .030, comp cam, high rise intake

I don't even know enough about engine rebuilding to be dangerous, but doesn't a high rise intake increase top end horsepower at the expense of low end torque? If that is happening, that is exactly the opposite of what you need for that boat. On a big heavy boat, torque is everything.

 

[racerone]

Step #1 would to weigh this boat.

 

[Faztbullet]

hooked up the threw hull exhaust ports, turns heads when it starts, comp cam, high rise intake​

These are your problems....
Thru hull does not exhaust out prop so you have no ventilation on blades...slow hole shot
High rise intake good for top end killed bottom end...slow hole shot

 

[Jgothing]

holy moly i didnt even think to consider all these ideas. this is all awesome stuff thats been brought to my attention, i have some homework do to. this is super helpful stuff. thank you guys so much. !

 

[jimmbo]

A High Rise Intake Itself isn't a Torque Killer, in fact the slightly longer Runners help Low end, though large Runners(volume) will.reduce low speed Torque. Any Single Plane Intake, would really kill the Low End