Is there anything wrong with being under proped?

[Equis]

Hello,<br /><br />I have a 2003 115hp Merc on my new boat (well, new to me)<br /><br />I read the max rec rpm is between 4750 - 5250 rpm<br /><br />Before I knew this handy piece of info, I ran it up to 5500rpm<br /><br />Someone told me to try with a full load so I had 8 people & heaps of gear in the boat and still got to 5250 (had more to go)<br /><br />The boat can do 65kph and is really fast to plane/plain? , I also get really good fuel economy.<br /><br />Would it be worth it to change the prop to a higher pitch?<br />Would I gain much speed or lose fuel economy or power?<br /><br />If I keep this prop would it do any harm if I didn’t run above the rec rpm’s?<br /><br />Thanks for all you help <br /><br />Rhys<br /><br />P.S when the engine is trimmed all the way down it works harder and sounds quieter so I was thinking more pitch would also make it work harder/run quieter, not sure about this one though..

 

[WillyBWright]

Re: Is there anything wrong with being under proped?

I'd go to a higher pitch. You can always keep that one for a spare or as a good pulling prop. Those motors don't tolerate overrevving too well. Shoot for 5250 with a "normal" load at full throttle.

 

[Clams Canino]

Re: Is there anything wrong with being under proped?

I'm with Willy.... those four cylinder 115's don't like to be overreved and have a nasty little habit of breaking crankshafts as the prefered method of complaining. <br /><br />I know you say you're gonna watch the tach.... watch it well then and be carefull.<br /><br />-W

 

[JasonJ]

Re: Is there anything wrong with being under proped?

I'd reprop. There is going to be that day when someone else will drive it, and will just run it wide open because there is an unfortunate amount of people who think that is what you are supposed to do in a boat. Better safe than sorry.

 

[tibb]

Re: Is there anything wrong with being under proped?

My humble opinion is to compare the price of your motor to the price of a new prop. Hmmmmm.<br />Sounds like a no brainer to me. <br /><br />Heat is a huge enemy to these cylinders and running a motor, even near it's max rpm, decreases the hour-life of the motor considerably.

 

[bigbrownbuku]

Re: Is there anything wrong with being under proped?

sounds like you could drop 2 inches and still reach max rpm easily. its like you say, as long as you keep an eye on the tach you arent doing any harm. the day will come when you arent the driver however.<br />you should have your tach checked also. seems to me the rev limiter should be hit by then.

 

[Winger Ed.]

Re: Is there anything wrong with being under proped?

If you're really serious about using your new boat, you'll need at least 6 props, and 4-5 more as spares along with a garage full of other bare necessitys we can get into later.<br /><br />For now though:<br /><br />I'd get a prop with 2 more inches of pitch, and check the tach's accuracy. If its as new as the engine- it should be real, real close if not dead on. Run it with a normal (for you) load in the boat, and go from there.<br /><br />Your speed may or may not change. But running that engine for extended periods above its recomended WOT will kill it.

 

[Equis]

Re: Is there anything wrong with being under proped?

Thanks Heaps for all your advice!<br /><br />Yep, I'll start saving up for a newie, sounds like the best plan <br /><br />6 Props? Ummm, your yanking my chain yes?<br /><br />Thanks<br /><br />Rhys

 

[Equis]

Re: Is there anything wrong with being under proped?

Was doing a Google and came up with these, anyone used one or are they crap?<br /><br /> http://www.boatpropellersaustralia.com.au/ <br /><br />Plastic or something...

 

[Clams Canino]

Re: Is there anything wrong with being under proped?

Originally posted by Equis:<br /> Yep, I'll start saving up for a newie, sounds like the best plan <br /><br />6 Props? Ummm, your yanking my chain yes?

You can get good used props cheap on Ebay. 6 props is kind of a joke, but the true disciples prolly have 3 or 4 - I know I do. Prop depends on my plans for the day.<br /><br />-W

 

[phatmanmike]

Re: Is there anything wrong with being under proped?

anyone used one or are they crap

you answered it yourself

 

[Winger Ed.]

Re: Is there anything wrong with being under proped?

Originally posted by Equis:<br />[QB] 6 Props? Ummm, your yanking my chain yes?<br />/QB]

pretty much, but you'll be amazed at how stuff accumulates,,,,,