What prop do you run on your 20'

[msojjo]

I am just trying to get closer to finding the correct prop for my 20 bowrider. I am still having a problem getting the boat on plane. I have a few items to correct on the motor that i will try this weekend. I had a vaccuum line disconnected from the throttle body, and i was running the motor on the dual batteries when i should be only running one, according to the manual. I'm running a 17 pitch ss michigan wheel balistic now. But i think i should be lower because with a 1/4 tank of gas and just me in the boat i can only get 4900 rpm wot and trimed up. Speedo says 55, so i'm guessing actual speed is 50 or 51, which is plenty fast for the lake that i do most of my boating on. The boat is 3300 empty so i add people gear and fuel i'm up to 4500 pretty easily. Anyone with a simular set-up?

 

[Tail_Gunner]

Re: What prop do you run on your 20'

Bear with us here and try to give as much info as possible..


ESSENTIAL DATA REQUIRED
When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions.
1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight
__________________

 

[Robbabob]

Re: What prop do you run on your 20'

You really have to answer everything possible from Tail Gunner's post.

Right off hand, I'd guess you have the right prop.... near empty load and probably just a hair over your WOT RPM spec. (just a guess), with a top speed that is probably ball-park for your boat. Do you think it should be faster top end as well as better off the line?

Since you are complaining about time to get on plane, are you sure your out drive is all the way down when you start? Some beginners start with a little trim up (that would be me ) and wonder why it takes so much longer compared to another operator (my girlfriend) on the same boat. Of course, that was a long time ago

Known engine problems should be corrected before any other set up is changed. By the way, I don't see what using both batteries would do to cause any issue with hole shot or overall speed.

Provide the rest of the info and you'll get some pretty good answers~

 

[msojjo]

Re: What prop do you run on your 20'

Bear with us here and try to give as much info as possible..


ESSENTIAL DATA REQUIRED
When posting a question about propellers, you cannot get a reasonable answer unless you provide the following information in your post: Items 1-4 are essential for meaningful response to most questions.
1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight



__________________

1) Trying to come out of the hole faster
2) Michigan Wheel Balistic 15X17 SS
3) 15X17
4) WOT 4900 at spedo 55mph, very light load 1/4 tank of gas and just me.
5) 350mag W/Bravo 1 1.5 gear ratio 300hp
6) 2000 Starcraft GT 2010, 20 feet and 3300lbs empty.

 

[msojjo]

Re: What prop do you run on your 20'

You really have to answer everything possible from Tail Gunner's post.

Right off hand, I'd guess you have the right prop.... near empty load and probably just a hair over your WOT RPM spec. (just a guess), with a top speed that is probably ball-park for your boat. Do you think it should be faster top end as well as better off the line?

Since you are complaining about time to get on plane, are you sure your out drive is all the way down when you start? Some beginners start with a little trim up (that would be me ) and wonder why it takes so much longer compared to another operator (my girlfriend) on the same boat. Of course, that was a long time ago

Known engine problems should be corrected before any other set up is changed. By the way, I don't see what using both batteries would do to cause any issue with hole shot or overall speed.

Provide the rest of the info and you'll get some pretty good answers~

I'm actually just under my wot, my max for my motor is 5000rpm. Top speed is great, i'm only guessing but if my spedo says 55, i think 51 or so is more accurate. I don't think that it should be faster top end, as i am only pushing a 17 pitch prop, i would just like more low end.

Ya, trim is all of the way down, i'm on my third boat now, been doing this for a while myself. This is just a new to me boat.

I'll be correcting my one known problem, my vaccuum line, and from what the manual says, it can interupt the ECM. It says and i quote "in either case, the ECM could shut off. When the voltage returns to the range that the ecm requires, the ECM will reset itself. The engine will now run normally. This ECM shut down usually happens so fast that the engine just appears to have an ignition miss." it says in bold letters "Do NOT operate engine with switches in Both or all position." I'm going to take it that that means something.

 

[Tail_Gunner]

Re: What prop do you run on your 20'

I'm actually just under my wot, my max for my motor is 5000rpm. Top speed is great, i'm only guessing but if my spedo says 55, i think 51 or so is more accurate. I don't think that it should be faster top end, as i am only pushing a 17 pitch prop, i would just like more low end.

Ya, trim is all of the way down, i'm on my third boat now, been doing this for a while myself. This is just a new to me boat.

I'll be correcting my one known problem, my vaccuum line, and from what the manual says, it can interupt the ECM. It says and i quote "in either case, the ECM could shut off. When the voltage returns to the range that the ecm requires, the ECM will reset itself. The engine will now run normally. This ECM shut down usually happens so fast that the engine just appears to have an ignition miss." it says in bold letters "Do NOT operate engine with switches in Both or all position." I'm going to take it that that means something.

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I'll be correcting my one known problem, my vaccuum line, and from what the manual says, it can interupt the ECM. It says and i quote "in either case, the ECM could shut off. When the voltage returns to the range that the ecm requires, the ECM will reset itself. The engine will now run normally. This ECM shut down usually happens so fast that the engine just appears to have an ignition miss." it says in bold letters "Do NOT operate engine with switches in Both or all position." I'm going to take it that that means something

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At what rpm does this split second miss occur?

Nice combo you have there....What performance character are you looking for

1. Total top end speed...5% of your boating occurs at 5200 rpm... that is..i hope.. only 5%

2. Hole shot and midrange punch..95% occurs there..

3. I am not opinionated...

 

[msojjo]

Re: What prop do you run on your 20'

Between 2500 and 3000 rpm. That's when i'm trying to get up on plane. and i can peg it at 3000 and it stays there until the boat is up, and it seems to take a bit longer when that miss occures. In a previous post i thought it was a dead spot, in the throttle range.

 

[Tail_Gunner]

Re: What prop do you run on your 20'

Is this a Throttle body motor or multiport...

 

[msojjo]

Re: What prop do you run on your 20'

Multi port fuel injection.

 

[Robbabob]

Re: What prop do you run on your 20'

Your engine is rated for 4600 to 5000. To gain better hole shot, you can pitch down an inch and watch yourself when you're light weight on the top end. Loaded, your WOT rpm should stay within spec.

As a reference to answer your actual thread title:
We have the CC Concept 21 Cuddy, which is 21' 9"
3,100 pounds dry
4,000 wet (usually 2 of us, full tank gas and lotsa bourbon/coke)
5.0 EFI 230 HP V/P engine (4400 to 4800 rpm)
prop is SS 14.25 X 21+

We push 4800 rpm half empty on glass
Average around 4600 RPM gased up and maybe others on board
top speed of 53 on speedo, haven't checked gps on phone
achieved same speed with additional 250 pounds at reduced rpm

Dual batteries in back
2 spare anchors in back
Ice chest behind passenger seat (farther back than we want)
Clothing and dry gear up front

Top end only for fun on glass to show off to guests on board. Else, we run around 3000 to 3500 rpm, 30 - 35 or so mph.

EDIT:
I see about 4 new posts and a lot of new information. This is a little old, but probably still on track toward end solution.

 

[Tail_Gunner]

Re: What prop do you run on your 20'

Multi port fuel injection.

Have you been in the I/O section and described this issue...The vacum line from the ecm to the intake is very simple. Have you confirmed the issue..I ask only because that is a lot of motor on a 20 and a 17 should pop you out of the hole..serious

 

[msojjo]

Re: What prop do you run on your 20'

Your engine is rated for 4600 to 5000. To gain better hole shot, you can pitch down an inch and watch yourself when you're light weight on the top end. Loaded, your WOT rpm should stay within spec.

As a reference to answer your actual thread title:
We have the CC Concept 21 Cuddy, which is 21' 9"
3,100 pounds dry
4,000 wet (usually 2 of us, full tank gas and lotsa bourbon/coke)
5.0 EFI 230 HP V/P engine (4400 to 4800 rpm)
prop is SS 14.25 X 21+

We push 4800 rpm half empty on glass
Average around 4600 RPM gased up and maybe others on board
top speed of 53 on speedo, haven't checked gps on phone
achieved same speed with additional 250 pounds at reduced rpm

Dual batteries in back
2 spare anchors in back
Ice chest behind passenger seat (farther back than we want)
Clothing and dry gear up front

Top end only for fun on glass to show off to guests on board. Else, we run around 3000 to 3500 rpm, 30 - 35 or so mph.

With your 21 pitch prop does it take a while to get out of the hole? We are at about the same amout of weight, and i have more horsepower with a much lower pitch prop and i'm still not getting out like i should.

 

[Tail_Gunner]

Re: What prop do you run on your 20'

Lets try to focus on the starcraft just for a sec:

• Manufacturer:Mercruiser
• Horsepower: 300 HP
• Years: All Years

• Model: Bravo One 350 Magnum Sterndrive
• Specs: Thru Hub Exhaust & 15 Tooth Spline, 4-? Gearcase
• Max RPM: 4800-5200 RPM

Those are the specs for a 2000 350 mag...But more importantly here is a miss....with the engine under a heavy load and sluggish out of the hole...You maybe be experiencing predetonation or knocking. This will severly cripple your boats performance..aka the ecm retards the timing down making the boat develop far less tourqe and hp



IT actually sounds like a interupt swiltch is engaging at 3000

 

[msojjo]

Re: What prop do you run on your 20'

Have you been in the I/O section and described this issue...The vacum line from the ecm to the intake is very simple. Have you confirmed the issue..I ask only because that is a lot of motor on a 20 and a 17 should pop you out of the hole..serious

It appears from a diagram of the vaccuum lines that it is going from the fuel pressure regulator to the throttle body. This is why i'm concerned, it's alot of motor with a very low pitch prop and still having trouble.

 

[msojjo]

Re: What prop do you run on your 20'

Lets try to focus on the starcraft just for a sec:

• Manufacturer:Mercruiser
• Horsepower: 300 HP
• Years: All Years

• Model: Bravo One 350 Magnum Sterndrive
• Specs: Thru Hub Exhaust & 15 Tooth Spline, 4-? Gearcase
• Max RPM: 4800-5200 RPM

Those are the specs for a 2000 350 mag...But more importantly here is a miss....with the engine under a heavy load and sluggish out of the hole...You maybe be experiencing predetonation or knocking. This will severly cripple your boats performance..aka the ecm retards the timing down making the boat develop far less tourqe and hp



IT actually sounds like a interupt swiltch is engaging at 3000

What is an interupt switch? Why would i be experiencing predetonation? How do i solve it?

 

[msojjo]

Re: What prop do you run on your 20'

By the way, yes i did post this in the merc section, but have no responses.

 

[Tail_Gunner]

Re: What prop do you run on your 20'

Take the issue to the I/O section..You will get some good info there. Try to be very spefic...Yr of the engine...Multiport ...mercruiser....slight hesitation at 3200 poor whole shot..No that is a slow and hard to plane problem...One on plane does it act smoother.. Good luck

 

[Tail_Gunner]

Re: What prop do you run on your 20'

By the way, yes i did post this in the merc section, but have no responses.

Its back to the top...lets stir the pot and see what we get

 

[QC]

Re: What prop do you run on your 20'

4900 RPM, 17 inch pitch, 1.5 ratio, 56 MPH = 4% negative slip. Something isn't right there. Period. Sort of impossible . . .

My guess is the tach is off, or the pitch is mismarked and I don't trust the speed either. This stuff has to be accurate or we can't dial this in.

 

[msojjo]

Re: What prop do you run on your 20'

4900 RPM, 17 inch pitch, 1.5 ratio, 56 MPH = 4% negative slip. Something isn't right there. Period. Sort of impossible . . .

My guess is the tach is off, or the pitch is mismarked and I don't trust the speed either. This stuff has to be accurate or we can't dial this in.

Well, the speed is on the speedo, not gps, haven't gotten a gps out on the water, i'm guessing i'm doing high forties, low fifties, the tach is brand new this summer, old one was jumping around on me, and the pitch on the prop is marked, and was not reworked. The prop is a michigan wheel balistic 15 x 17 three blade ss. I guess my speedo could be way off, maybe even cruising in the mid forties i guess. It sure feels like i'm flying though. But your right i don't think that i should be getting that much top end on a 17 pitch prop.