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NickG

Hill Marine 4x4 prop on Sig 250

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Can’t find much info for my specific application, but I want to drop the cruise RPM range for my boat. I’m told the Hill Marine 4x4 prop will do just that. The pic shown is where my boat feels best, but I’d like to drop the RPM’s closer to 3500 at this speed (or whatever the true speed is when the speedo shows this).  Anyone have much to say about my setup?
 

2008 Chaparral Signature 250 (true 25’ hull with 2’ swim platform)

Mag 350 Bravo 3 with original 2.2 ratio and 3x3 22 pitch prop

Current read:

 

FBCAC54F-3BB2-4227-8DEA-A5E24BB7A957.jpeg

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Always need to juggle ......desired cruise speed / rpms....  WOT rpms.   

I like a boat that has about 32 mph & 3200 rpms.  Not always possible unless you have a lot of props to pick from.   Like a Alpha Drive.   Caution  That big of a spread might be a very slippy prop.  Not very efficient with the power being put into it. Is the hull free of ALL drag ? weeds & animals ?

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Hull is clean. Bottom painted with the good stuff. 
No way I’ll see 32 at 3200 with this single screw at 6900 lbs.  I’d take that in a heartbeat. 
 

I’ll give up top end for 30 at 3500

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 Get a good hand held GPS  for accurate speed.   Then get a  portable tachometer to Check your boat one against.  Crawl under your tachometer see if it has a small slide switch on the back of it. It may be set to the wrong number of cylinders..  4..6.. or 8 are the numbers of cylinders to pick from.

Lastly see if your prop has a solid bite.  Slowly trim the drive up and down to find the peak.  Can you reach a peak without going TOO FAR UP trim ?  Careful with that. You can destroy the U joints .    The bilge pump is keeping it reasonably empty when on plane ?  

Do you have another boater to run with you at cruising speed ?  Yes ?   Have him watch you boat angle at planing speeds it might look slightly wrong / causing loss of speed.

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I’m not sure what the issue here is.  Do those numbers look odd?

I also have the Mercury Smartcraft gauge and it pretty much coincides with the analog tach.  Speeds also are close to mobile device GPS readings. 

Those gauges are relatively accurate. The little bit of reading I found from others with my type of boat/power have similar numbers. 

Is there something wrong here?

43BF39B1-3C17-4FFD-B3E3-A3EA8EB01CE7.jpeg

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I used the hill marine 4x4 prop on my cruiser several boats ago. Stayed with the same pitch and the cruise rpm dropped a few hundred for the same speed. Holeshot and top end were not impacted. Responded to trim better, and held in the turns better. I was very satisfied. 
tried them on the next boat which was a 29’ open bow with a 496, they did not perform. Ended up with the Merc 4x3 for that boat which worked better.

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Nick, what is you WOT RPM now? If it's at or near rated rpm for you engine, then that is the first consideration before adding pitch, cup, or diameter. What you don't want to do is lug the engine as it needs to be between 3,100 and 3,450 for best cruise efficiency and longevity.  W

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Wingnut is correct (as usual).  Your boat needs to be propped so that WOT RPM’s are within the recommended range for your motor. If you add pitch to drop your cruise RPM’s you could drop below this range, and you will “lug” the engine, which leads to premature engine failure. You have a lot of boat for a 350MAG to push. With your 2.2 B3 drive ratio, 22’s sound about right. But a sea-trial WOT will tell the story...

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My 6.2L is very happy cruising at 3400 RPM. No clue what the speed is but the boat just feels right at that range. 

 

Call Hill and chat with them. They have a loaner program so you can give them a try. 

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Paul said rpms dropped but speed was the same

THat is ALWAYS a sure sign the original prop company made a very inefficient  /  slipping excessively prop.  Bad designed props can EAT horsepower very silently. Do a Phillbo . Get all the data ready .  Upper & lower   S D gear ratio. Present prop P & D & # of blades . Material.  

Are any of the props blades dented or bent?   Hill prop place needs all that info.  

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My WOT is right at 4800-5000, so a pitch change is not a goal. What I’m lead to understand is that the 4x4 prop at the same pitch will bite harder and give less speed robbing “slip” than the 3x3. 

I spoke to the older Hill in California and he suggested no pitch change and was adamant that, if I’m not looking for more top end and am happy with the hole shot, the 4x4 would certainly drop cruise RPM’s while the changes elsewhere would be insignificant. 

I was hoping to hear real world experience. Not really finding it with my exact setup.  

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1 hour ago, NickG said:

My WOT is right at 4800-5000, so a pitch change is not a goal. What I’m lead to understand is that the 4x4 prop at the same pitch will bite harder and give less speed robbing “slip” than the 3x3. 

I spoke to the older Hill in California and he suggested no pitch change and was adamant that, if I’m not looking for more top end and am happy with the hole shot, the 4x4 would certainly drop cruise RPM’s while the changes elsewhere would be insignificant. 

I was hoping to hear real world experience. Not really finding it with my exact setup.  

As I mentioned above, I stayed the same at WOT and hole shot was unchanged. I did go lower by a few hundred RPM for the same speed in the mid band.

27' Cruiser with 350 mag.

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30 minutes ago, paulswagelock said:

As I mentioned above, I stayed the same at WOT and hole shot was unchanged. I did go lower by a few hundred RPM for the same speed in the mid band.

27' Cruiser with 350 mag.

I love this encouragement!  

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4 hours ago, cyclops2 said:

Finding a more efficient prop is not really that easy.  

 

Which is why I’m making phone calls, asking questions on a boating site where someone might be familiar with my boat, and listening to advice.   It’s a lot to learn. 

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The Hill 4X4 props have a great reputation.    
But i don’t think you are going to see that much drop in RPM at a given speed, but if that is your goal, the 4X4’s are the way to go. I had my factory B3 props redone by Bronson Hill Marine in 2005 when the boat was new. I gained 3 mph in speed at cruise RPM’s and increased 200 RPM at WOT. Seat of the pants says it was more, but I was happy. 

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I can say there are  /  is a  lot of luck with finding a ............SATISFYING .........prop.  

My 2002  186 SSI with the 305 V8 220 hp carb engine in that heavy wide hull had the right SPEED prop with just me in it. Revlimiter holding 4800 rpms &  GPS first spring run with no painted bottom . Trimmed out perfectly for straight ahead.      WAAAHOOO  !

But the prop " blew air instantly if floored under a full planning speed.  NO grip at all. I blew completely out if turned suddenly at  almost any planing speed.  I think the Planing Pad helped a great deal for a great WOT speed.  But created the blow outs all the time.      So what do I do to stop the blow outs.   Over size the daylights out of the prop ?    Here comes my favorite saying............ Better to be lucky than have a lot of wisdom.....................I called Prop Gods in 2006 ?   Old mind.   He recommended 2 series of props. What did I know about Power Tech Props ?  NOTHING  I then called Power Tech directly & finally got to Technical Support. I asked for the most experienced person to handle my problem.  The person First asks me how much speed I am willing to lose.  Odd I thought. I said take it all if it stops BLOW OUTS completely.  He was very persistent about losing top speed . I agree to the most grippy style.  

I floor the engine idling in gear.  It almost stalled the great running engine. I had gone from a instant BLOW OUT to almost  stallingthe motor.  2 more prop swaps with just shipping charges. I was racing & turning with most  PWC nuts.  BUT  I was now down to 45 GPS & 4400 rpms wot . Excellent fuel mileage.   I could turn the boat so sharp & fast that the G force compressed the air in my lungs enough to force a gasp out of me.

The prop has  RIDGES on the edges of the blades. Looks like a total  REJECT.  But does what I want perfectly. Pure luck.

Props are just like tires on a powerful car.  Critical.   Who do you believe when wanting a great handling tire ?

Get lucky.  Be persistent  On getting the percent of slippage the props have.

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I had a buddy with a cruiser that had to run pretty much WOT to stay on plane. He went with the Hill 4 blade props and loved the improvement. 

 

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10 hours ago, Phillbo said:

I had a buddy with a cruiser that had to run pretty much WOT to stay on plane. He went with the Hill 4 blade props and loved the improvement. 

 

I have not heard a bad thing about them and I like this from a cruiser perspective.  

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13 hours ago, cyclops2 said:

I can say there are  /  is a  lot of luck with finding a ............SATISFYING .........prop.  

My 2002  186 SSI with the 305 V8 220 hp carb engine in that heavy wide hull had the right SPEED prop with just me in it. Revlimiter holding 4800 rpms &  GPS first spring run with no painted bottom . Trimmed out perfectly for straight ahead.      WAAAHOOO  !

But the prop " blew air instantly if floored under a full planning speed.  NO grip at all. I blew completely out if turned suddenly at  almost any planing speed.  I think the Planing Pad helped a great deal for a great WOT speed.  But created the blow outs all the time.      So what do I do to stop the blow outs.   Over size the daylights out of the prop ?    Here comes my favorite saying............ Better to be lucky than have a lot of wisdom.....................I called Prop Gods in 2006 ?   Old mind.   He recommended 2 series of props. What did I know about Power Tech Props ?  NOTHING  I then called Power Tech directly & finally got to Technical Support. I asked for the most experienced person to handle my problem.  The person First asks me how much speed I am willing to lose.  Odd I thought. I said take it all if it stops BLOW OUTS completely.  He was very persistent about losing top speed . I agree to the most grippy style.  

I floor the engine idling in gear.  It almost stalled the great running engine. I had gone from a instant BLOW OUT to almost  stallingthe motor.  2 more prop swaps with just shipping charges. I was racing & turning with most  PWC nuts.  BUT  I was now down to 45 GPS & 4400 rpms wot . Excellent fuel mileage.   I could turn the boat so sharp & fast that the G force compressed the air in my lungs enough to force a gasp out of me.

The prop has  RIDGES on the edges of the blades. Looks like a total  REJECT.  But does what I want perfectly. Pure luck.

Props are just like tires on a powerful car.  Critical.   Who do you believe when wanting a great handling tire ?

Get lucky.  Be persistent  On getting the percent of slippage the props have.

All I know is that I want to go for a ride in your boat now. I want to feel those G’s!  

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