I hate to ask.. But i got to

[Tommywalton]

Ok here goes, i read sticky and tons of other prop threads.
1. 2300 (23') chaparral with 5.7, maybe 250 horse. Good ignition good running engine and its in time.
2.unknown weight
3. Omc cobra 800 outdrive
4.stainless Michigan 14"x19" pitch three blade prop. Good condition
5. With 2 people the boat pull hard and planes quickly for a boat this size.
With proper trim it tops out at 48 mph gps around 4200 rpm

The problem is when i load it like today with 7 people it takes FOREVER to plane and puts engine in a strain the whole way. After it gets to 40mph, top speed loaded, engine is at 3900rpm.

I want to tow more than cruise. And right now it wouldnt tow a turd on a kite string. Pathetic. Also at 20mph, wake oarding speed its between planing and off plane. Im thinking of buying a prop from here aluminum, 14.5x17 4 blade. What are your thoughts? Im totallyo ok loosing top end if i can have great power down low. Is this 4 blade good for me? Going fro 3 blade to for i read i should go down 1" pitch to keep the same reaults. I want tow boat. Should i go 4 blade 16" pitch?

 

[steelespike]

Re: I hate to ask.. But i got to

Good job but we need the year.
A 16'4 bld. seems reasonable though a light load may put you over 4600 but you can control that.
You should stick with same material and brand for more predictable results.
If it makes 4600 at 10% slip speed would be about 44.
But should have good hole shot and stay on plane easier at reduced throttle.Responce
around the dock should be better.Keep in mind prop selection isn't carved in stone.

 

[Philster]

Re: I hate to ask.. But i got to

steelespike owns this forum; he's a stickler for details alright!

I'm just chum here, but I will add this: 19p seems right for fresh from factory. 7 people is a LOAD. You are pretty much required to find this setup (so I am not bucking steelespike here. But when you come back with all info, keep this in mind):

When you get it set up right, you can't be tinkering with seven people on board, so fill the tank, have all your gear on board, and you'd better be shooting for the redline (not the minimum RPM within the max RPM range). You, your fuel, and your gear should be getting that engine near redline... so...

...then, when you add your full load of people, the max engine RPM will probably drop near the bottom of the acceptable RPM range at WOT. That is acceptable. With seven people on board, I would say you are best to manage the throttle and not try to push it. Sort of like a truck pulling a large boat: take it easy. Boats have one gear. You need to minimize the suffering the engine takes, because their is no transmission to do that for you.

 

[steelespike]

Re: I hate to ask.. But i got to

I am by no means "the guy" I do spend intirely too much time here. Just hope in the process I can help out.
The year can help confirm the gear ratio. In this case I just checked the first 800 series 5.7 I saw in 1984.
1.41 ratio
Philster makes some very good points.I hope he doesn't hesitate to add his take on a problem or solution.

 

[Tommywalton]

Re: I hate to ask.. But i got to

Sorry, its a 1988. And btw it came with a 21" aluminum 3 blade. The original owner did say that on the first trip to the lake he tried to pull up his 80lb son on 2 skis and it wouldn't. Thats when he bought the michigan 14x19 back in 1989. Oh also i ground the prop up on the hwy rewelded to add material and polished it down so i know its garbage now. But these problems im speaking of were before the repair. The engine is a gmpp crate 350 rated at 260hp. Very mild factory cam. This motor came out of my other boat. 1986 bayliner 1950. It had the same problem when i got it to. 21" pitch. I bought a piranha kit with 19" and 17" blades. I never ran anything but the 17

I can handle the high rpm issue. If i want to clown and haul butt i will just run the 19.
Any other info you guys need?

 

[Philster]

Re: I hate to ask.. But i got to

I'm confused. We'll blame you. Haha.

19P is too much when you are hauling seven adults -- right? Okay, it is better to be propped so that there are times when the engine has the potential to be over-revved than it is to be prop so that there are times when the engine has the potential to be lugged (strained/stress to the point it can't reach max RPM range w/given load).

Personally, on a 23' boat, I'd think seven full-sized adults is pushing it, no matter what the capacity plate says. But, back to the point I was making....

If you want to under-prop your boat because you will carry a huge load from time to time, then as long as you are smart enough to be your own rev limiter, I say to go ahead and drop pitch. Every time you don't have that big load, you will pay for it, because the boat will have a lower top speed (limited by you, the human rev limiter) and you will burn some modest am't of extra fuel (maybe not too bad really).

None of this is odd or bizarre. Hundreds of thousands of cars out there can blow the redline. They are all 'under-propped' (under-geared) in all of their lower gears, and the ones without electronic rev limiters have human rev limiters.

And... I just read your info again, and it doesn't sound like you should even be running the 19 w/light load.

 

[steelespike]

Re: I hate to ask.. But i got to

It seems we're working with "best recollection" specs or those coming from your admitted "Garbage prop".
If actual specs from your garbage prop the numbers are pretty good.Except as already stated not good for a big load.
If numbers are best recollection they may be a couple of hundred rpm off + or -.
A 16 may not be accurate.

 

[Tommywalton]

Re: I hate to ask.. But i got to

Im sure im to blame! I think im going to go with a 17" pitch. The whole deal with the 16 is that i read on this forum in more than one place when going from a 3 blade to a 4 drop 1 inch pitch to keep the same results with top speed. Do you see what i mean? If i put on a 18 pitch 4 blade it will be almost identical to my 19 3 blade. So thats why i asked about the 16. I want a 4 blade not a 3. Also why not just build a bulletproof forged crank, roller 350 with 400hp and 6k redline? Add about 150 hp. I know how all this works on the street but ive learned in the water is not even similar.

 

[steelespike]

Re: I hate to ask.. But i got to

Biggest problem with high performance on the water is rpm.On land a typical motor is at peak rpm for a few seconds.On water could be hours for those with a lead foot.Thus the 4600 to 5000 typical max rpm
for an I/O on the water.
The 1" drop is to maintain rpm.Yours is a little low now if your often running a heavy load with recreation.
Seems to me a 16 would do better at keeping rpm closer to that required.Unfortunately the 16" likely
will have fewer selections available and you will need to watch rpm carefully with a light load.
Some folks run 2 props for ideal numbers under both requirements.

 

[Tommywalton]

Re: I hate to ask.. But i got to

My thoughts exactly on the 2 props. I used a 19 and 17 on my other boat. A piranha. Changed in the water often. Keep extra nuts!! I will tow most of the time and keep the 19 on hand for quick change. I think i will go with a 17" 4 blade first. On the engine deal i mentioned it because im going to rebuilt it this winter.

It has a noisy wrist pin so if it makes it all summer its getting built. This is a whole other thread but im thinking, vortec heads, dual plane with marine carb and marine new distributor with timing shunt, 9.5 compression. I live 60 miles from memphis so i will get comp or crane to grind me a cam for 4500 peak with smooth curve. Oh and roller valve train. I may get 375hp through those risers