Prop Pitch Question

[KFS]

Boat is a 19' Chaparral 1930 ss Sport - weight lists as just under 3000 pounds.
5.0/305 Mercruiser Alpha Outdrive
3 fin
Alum
14.5 x 17 Pitch [Additional Info Added/Corrected]
New (to us) so Performance Numbers as yet unknown.

In looking at our new (to us) boat a knowledgeable friend expressed surprised that our prop has such a low Pitch? Said that was extremely low and that we would have to watch not going full throttle for danger of some damage to motor? (Forgive me, I'm way in over my head here can you tell? Husband is out of town and said "ask your people" -- so now I have "people"

Is this an issue or not? Would you change it? Live with it?

Forgive us. We just bought this boat yesterday and it checked out beautifully at the mechanic inspection but we are being obsessive. We have purchased a beautiful, healthy boat and we are pretty committed to not doing anything to screw that up.

 

[Maclin]

Re: Prop Pitch Question

The 16.5 number sounds more like a diameter to me. Pitches are rarely in half inch increments.

What brand prop, how many blades, aluminum or stainless steel, what are your performance numbers it achieves now, like WOT RPM and MPH.

 

[KFS]

Re: Prop Pitch Question

The 16.5 number sounds more like a diameter to me. Pitches are rarely in half inch increments.

What brand prop, how many blades, aluminum or stainless steel, what are your performance numbers it achieves now, like WOT RPM and MPH.

Will check that and report back. We just bought the boat yesterday and are still in the "getting to know you" phase. Right now she's parked next to the swimming pool as if poised for a particularly ill-advised launch. We did get a test drive and mechanic's check but we want to be sure we are starting out right.

 

[Maclin]

Re: Prop Pitch Question

Best thing to start with is what RPM does the engine get to at WOT (wide open throttle), and what MPH the boat gets to when trimmed properly at that WOT RPM. If those are in line then just keep on playing...

 

[jestor68]

Re: Prop Pitch Question

Since the largest diameter propeller that will fit on the Mercruiser Alpha drive is 16 inches in diameter, it appears someone is not reading the numbers correctly. As others have mentioned, diameters can include fractions of an inch(14-1/2, 15-1/2) but standard pitch sizes are whole numbers(15,17,18,19,etc).

Somewhere on the prop should be stamped diameter and pitch; example 14-1/2 X 19. It may be necessary to remove the prop(depending on brand) to read the numbers. Sometimes they're stamped on the end of the propeller hub, covered by the washer and nut that hold the prop on.

If you took it for test ride, did the seller run it wide open(full speed)? If not(or you didn't notice the rpm) the first thing you'll need to check when you run the boat yourself is the full throttle rpm as indicated on the tachometer. Do not exceed 4800-5000 rpm. As long as the engine stays within it's full throttle operating rpm range (4000-5000rpm), you're fine. Ideal would be 4600-4800 with a "normal" load in the boat.

 

[KFS]

Re: Prop Pitch Question

Since the largest diameter propeller that will fit on the Mercruiser Alpha drive is 16 inches in diameter, it appears someone is not reading the numbers correctly. As others have mentioned, diameters can include fractions of an inch(14-1/2, 15-1/2) but standard pitch sizes are whole numbers(15,17,18,19,etc).

Somewhere on the prop should be stamped diameter and pitch; example 14-1/2 X 19. It may be necessary to remove the prop(depending on brand) to read the numbers. Sometimes they're stamped on the end of the propeller hub, covered by the washer and nut that hold the prop on.

If you took it for test ride, did the seller run it wide open(full speed)? If not(or you didn't notice the rpm) the first thing you'll need to check when you run the boat yourself is the full throttle rpm as indicated on the tachometer. Do not exceed 4800-5000 rpm. As long as the engine stays within it's full throttle operating rpm range (4000-5000rpm), you're fine. Ideal would be 4600-4800 with a "normal" load in the boat.

Thank you! Will double check the numbers in daylight but I suspect he just read them wrong. I appreciate the prompt replies. DH and I didn't think it sounded right but we didn't want to damage anything - or anyone - through ignorance.

 

[KFS]

Re: Prop Pitch Question

Best thing to start with is what RPM does the engine get to at WOT (wide open throttle), and what MPH the boat gets to when trimmed properly at that WOT RPM. If those are in line then just keep on playing...

That's what we wanted to hear. Thank you!

 

[Maclin]

Re: Prop Pitch Question

From your other posts in the Boating section, I think you got a really good boat and I tend to think you are good to go, just watch the tach until you get used to everything

 

[spdracr39]

Re: Prop Pitch Question

Just an FYI I have a 5.0/genII my outdrive ratio is 1.5 and a 17 pitch prop is perfect for me. If you have a 1.62 it may be a little low.

 

[KFS]

Re: Prop Pitch Question

From your other posts in the Boating section, I think you got a really good boat and I tend to think you are good to go, just watch the tach until you get used to everything

Thank you! We think we did too and we don't want to be the ones to ruin that

Just an FYI I have a 5.0/genII my outdrive ratio is 1.5 and a 17 pitch prop is perfect for me. If you have a 1.62 it may be a little low.

Thank you. Experienced input very much appreciated!

 

[pvieira]

Re: Prop Pitch Question

I already have bowrider sea ray 200 year 2002 with mercruiser alpha 1 sterndrive and 5.0 mpi 260 hp.
They have a serious poor boat perfomance.with mercury veneance ss prop 3 blades pitch 19",take a lot of hours,the
boat to plane on the water,loaded with half gas tank and 5 adults and 1 small kid.no towing anybody.if there any solution. Baottest.com said that for this boat with standart package ,top end speed is over 51 mph.
Do i have to change propeller for a mercury high five ( 5 blades) ss with same pitch (19) im thinking also to add cavitation plate " stingray" for help the boat ,loaded with people and gas,for better plane and do it quickly as you push the throttle. Stern drive is alpha 1,62 gear ratio. Also have to come down in ptch 17" always in high five for better results.
.thank for your advise.

Pablo

 

[spdracr39]

Re: Prop Pitch Question

Don't be a hijacker. Start your own thread or you will get no answers.

 

[pvieira]

Re: Prop Pitch Question

Don't be a hijacker. Start your own thread or you will get no answers.

spdracr39 first of all i?m not a hijacker of nobody and nothing.I think this is a public forum to help boaters all over the world
who friendly wants to share their boating experience and help to solve similar navigation troubles with other boaters.Thats because I expose my problem to the forum,thru this question because i think of good faith somebody could advice me on
a similar navigation problem as you could have.Now I have two things clear : I DONT WANT YOUR HELP AND I DONT LIKE THIS SYSTEM. BYE,

 

[steelespike]

Re: Prop Pitch Question

Pablo Hopefully your still around.S 39 could have been more subtle.
You need to do your own thread it gets very confusing when they get mixed imagine what it would be like if you had 3 or 4 problems in the one thread.
You will get clearer, faster responses in your own thread. There is a new thread tab at the top of the prop forum.