The Right Prop??

[iwldntli2u]

1981 Mercruiser 120 4 cycl inboard w/ Mercruiser 1/R stern drive. Stern drive has a sceg. Currently i have a 13 3/4 P19 prop. I get about 3900 - 4000 RPM at 36 or 37knts. Can anyone suggest a prop or does the prop i have go with this setup. Looking for a new prop and getting alot of different stories<br /><br />Thanks-

 

[Dhadley]

Re: The Right Prop??

Since the I/O does not have the ability to raise the X dimension easily you are limited to prop changes to get your rpm changes. I'm guessing you want to increase rpm's.<br /><br />Tell us more about what youre looking for (in rpm) and your present prop. 13 3/4 Is kind of an odd diameter for a 3 blade, is it a 4 blade?<br /><br />Good luck!

 

[iwldntli2u]

Re: The Right Prop??

I am looking for more RPM. The current prop boggs the engine to much. My current prop is a around 13 at a 19 pitch. I talked with some other boat fellows and they suggest i go to a 16 ro 17 pitch and around 13 in diamater. Does this sound right?

 

[DJ]

Re: The Right Prop??

Ski Rob,<br /><br />You can figure 200 RPM (up or down) for every inch in pitch. A 17" sounds just about right.

 

[adrew]

Re: The Right Prop??

I agree. Even a 15 inch pitch with a "cup" on it might be good if you want to ski or get a good hole shot. Just be careful to not over rev the engine.

 

[Dhadley]

Re: The Right Prop??

Lets get to the basics. Is it a 3 blade or 4? Is it stainless or aluminum? What brand? Is the motor running correctly (including timing)?<br /><br />let us know!

 

[Bondo]

Re: The Right Prop??

The basics are you need more rpms... go to a 17" prop... The Dia. is figured out For You(the engineers figure this out when they design the prop, you Don't get to pick, or choose)... Just drop down 2" in pitch, In a prop of the same style as you have now....<br /><br />Or, go to the beach with your buds, borrow their props,+ test them till you find one that gives you the results you're looking for... Then go buy a copy of that one for yourself....

 

[Doug Durako]

Re: The Right Prop??

Ski Rob----there are three or four other prop threads out here if you want to read more discussion.<br /><br />I agree with Bondo----find someone with your rig and borrow. Go with stainless steel if you can, but at 300 to 400 bucks a pop, I like to try before I buy.

 

[iwldntli2u]

Re: The Right Prop??

Dhadley- My current prop is a mercury stainless steel with 3 blades. As far as i know the motor is running fine. I will check the timing incase.<br />thanks for yours and everyone elses help.

 

[Dhadley]

Re: The Right Prop??

Ski Bob - let me know how you make out. As a performance center we do work with folks on getting the right prop. Most shops want to sell you "a prop" and hope youre happy. A performance center will make SURE youre happy. And yes there are choices on diameter as well as pitch.<br /><br />Keep us informed!

 

[iwldntli2u]

Re: The Right Prop??

do you have any sugesstions for this setup-<br />Thanks-

 

[Dhadley]

Re: The Right Prop??

Once we verify the motor is running correctly (test wheel) I would try some props in the 15" to 16" range. There are some "over/thru" props that allow the prop to vent or slip slightly when getting on plane. This allows the motor to get into the "power band" quickly. This is particularily helpful when the power to weight ratio is down. <br /><br />Then we would look at the type of prop. Obviously a prop with a lot of lift will carry the hull better which reduces drag and increases speed and rpm. There are specific props made for I/O's that run deep as compared to an outboard that has the ability to change the X dimension and get the prop closer to the surface.<br /><br />The most difficult thing is trying to compare one brand or style to another. A 19" Stiletto may perform differently than your 19" Quicksilver. It will definately not be the same as a Turbo 19".<br /><br />I know all this sounds a bit complicated but after you determine the motor is CAPEABLE of more rpm its really easy. Just make sure the motor isnt whats holding back the rpm's.<br /><br />Good luck!