Hurricane Sundeck 217 with Merc 125 Prop confusion

[rgiordano73]

I own a 2001 Hurricane Sundeck 217 with a Mercury 2-Stroke 125 and I need to replace the prop and I'm greatly confused. Right now my top speed on the boat is about 22 and I'd like to get more speed out of it. Does anybody have a set up like this and could you recommend a propeller and what would be the proper pitch.

 

[Bob_VT]

Re: Hurricane Sundeck 217 with Merc 125 Prop confusion

I will move this to the propeller section.

Welcome to iboats.

Read the sticky posts in the prop section which will help!

 

[rgiordano73]

Re: Hurricane Sundeck 217 with Merc 125 Prop confusion

I will move this to the propeller section.

Welcome to iboats.

Read the sticky posts in the prop section which will help!

Thanks.

So now having read the sticky. Here's the rest of the story:

2001 Hurricane Sundeck 217 with a 2001 Mercury 125 2+2 saltwater, which was rebuilt last year.

As for the current prop on the boat, I'm not sure at all, I know it's aluminum and the boat came with an old prop which is 13.25 x 17 so I suspect is the same.

the WOT RPM is 5250 and usually I have about 700 - 800 lbs aboard the boat.

I'd like to get more speed out of this boat as of now the top speed is about 22 mph.

Any help would be appreciated.

 

[jestor68]

Re: Hurricane Sundeck 217 with Merc 125 Prop confusion

You have a 20'10" 3400 lb boat being operated with 55% of it's rated power(225).

Dropping pitch to next lower size(15) will gain 300-400rpm and possibly pick up a little top speed, as well as helping all around performance.

But the real answer is more power.

 

[rgiordano73]

Re: Hurricane Sundeck 217 with Merc 125 Prop confusion

You have a 20'10" 4400 lb boat being operated with 55% of it's rated power(225).

Dropping pitch to next lower size(15) will gain 300-400rpm and possibly pick up a little top speed, as well as helping all around performance.

But the real answer is more power.

So heres an update: I bought a new 13.25 x 17 Black Diamond Prop and put it on the boat. Put the usuall load on the boat and went for a spin, no increase in speed but I maxed out at 4000 RPMs at WOT. So now I'm more confused. Same specs as the old prop, different maker but lower RPMs and the same speed.

I'm thinking of putting on a 15 pitch propeller as it seems I have some extra RPMs to give.

Any thoughts?

 

[jestor68]

Re: Hurricane Sundeck 217 with Merc 125 Prop confusion

If the rpm was 5250 before, and putting a 17" on it dropped it to 4000; that means the previous prop was something less than a 17". It's possible it was a 13"? Because 5250 is an acceptable rpm with a load of 3400 lbs.

Since each 2" of pitch change result in 300-400 rpm change, putting a 15" on there should result in about 4400 rpm at WOT. Since this is the bottom of your Merc's rpm range, it will be necessary to drop lower than 15" to get the rpm up where it should be.

I suggest you remove the extra weight from the boat and test with a light load to achieve an rpm that's near the top (5500rpm)of it's range. Then when loaded, it will pull it down a few hundred, but still be around the middle of it's rpm range(5000+/-).

Double check the accuracy of your tachometer.

Since you're dealing with a situation of being under powered, you may be hard pressed to achieve 30mph with that load. The important thing is for the motor to be able to spin up to the proper rpm.

 

[rgiordano73]

Re: Hurricane Sundeck 217 with Merc 125 Prop confusion

If the rpm was 5250 before, and putting a 17" on it dropped it to 4000; that means the previous prop was something less than a 17". It's possible it was a 13"? Because 5250 is an acceptable rpm with a load of 3400 lbs.

Since each 2" of pitch change result in 300-400 rpm change, putting a 15" on there should result in about 4400 rpm at WOT. Since this is the bottom of your Merc's rpm range, it will be necessary to drop lower than 15" to get the rpm up where it should be.

I suggest you remove the extra weight from the boat and test with a light load to achieve an rpm that's near the top (5500rpm)of it's range. Then when loaded, it will pull it down a few hundred, but still be around the middle of it's rpm range(5000+/-).

Double check the accuracy of your tachometer.

Since you're dealing with a situation of being under powered, you may be hard pressed to achieve 30mph with that load. The important thing is for the motor to be able to spin up to the proper rpm.

jestor,

Thanks for the advice. I've checked the old prop and it's a 17, so I now suspect that my tachometer might not be giving me a good reading. I plan on switching props to the old prop and seeing what the tack reads.

I also took out the boat and did a GPS speed test with the new prop and I'm getting 26mph out of the boat at around 4000 rpm (but that may be a bad tach).

Any thoughts on how I can check the accuracy of the tachometer?