Prop for 3.0ltr ALpha 1 on Maxum 1800SR

[donie]

Hi all<br /><br />Can I get some advice on prop selection please. I have actually bought a prop with a 15 degree pitch for this boat as I'm using it for wakeboarding at 20mph. It pulls lovley with this prop.<br /><br />My problem is, what happens if somebody powers it up. How do I work out the max rpm I should pust this prop to. What effect has the WOT rating on the prop selection. I think the 3.0 ltr has a WOT of 4800. Somebody correct me if I'm wrong.<br /><br />Thanks for any help<br />Donie

 

[rogerwa]

Re: Prop for 3.0ltr ALpha 1 on Maxum 1800SR

I have an 3.0l and my WOT is 4200-4600. Depending on the year of yours it may be as you suggest.<br /><br />Regardless of your prop, you should not exceed your recommended WOT. If you prop will do 5200, don't let the driver do 5200. In fact, I rarely do WOT because I don't want to shorten the life of my engine. I try to stay at 3/4 of recommended WOT.<br /><br />The RPM rules are consistent. If you are underpropped, you will just go slower for the same RPM.

 

[donie]

Re: Prop for 3.0ltr ALpha 1 on Maxum 1800SR

Thanks for that.<br /><br />I think I understand now that the WOT rating is the max rpm that the engine is rated for and pushing it beyond that is not good sense. <br /><br />So for my prop selection the load on the engine is lighter so the WOT rpm will obviously be higher. <br /><br />I presume you can get devices to limit the WOT rpm but is it just down to trusting the driver and watching the rpm gauge. Or should I adjust the the trottle to go to max 4800. I presume this doesn't work too well depending on how the boat is loaded?<br /><br />Thanks for the help<br />Donie

 

[rogerwa]

Re: Prop for 3.0ltr ALpha 1 on Maxum 1800SR

Many people have different props for different uses. A higher pitch prop will give you more speed and less holeshot. Each 1" increase in pitch will reduce the achieved WOT by about 200RPM.<br /><br />If you go to a higher pitch prop you need to make sure you can achieve the recommended WOT or your boat will be considered overpropped and could cause damage to your engine by overworking. As far as underpropping is concerned, you just need to make sure you don't over-rev the engine..<br /><br />I would stick to informing the driver not to exceed a certain RPM. You don't want to mess with adjusting the controls.

 

[Doug Durako]

Re: Prop for 3.0ltr ALpha 1 on Maxum 1800SR

Personally, I would not run a prop that allows the motor to exceed recommended maximum rpm at wide open throttle. Somebody is going to punch that throttle when you aren't looking!<br /><br />We've been slalom skiing for 30 years and have pulled people at WOT many, many hours on all of our boats to reach desired course speeds, especially when carrying a load of people. This does not hurt the motor or unit, as long as the oil is good.<br /><br />I change oil in the motor and lower unit at the beginning of each boating season and every 40 hours after that---It's like a religion with me, and I think it is the cheapest way to avoid big problems in your engine and unit.