WOT Question

[flingus]

Quick question on WOT.. I want to see if I have the best prop on my boat but, I want to make sure I have all the required info before I really ask..

I'm going to test my WOT this weekend on the lake but, I want to make sure I have the definition correct..

Am I to basically push the throttle all the way forward, and see how fast I can get my boat to go? And I'm assuming if my rpm's start getting out of hand, I should back off and list the mph and safe max rpm when I ask about prop size?

The reason I ask is.. I think if I go WOT for say, more than 30 seconds I think the engine will go over my safe range of RPM's. Not sure yet because I have never tried to go that fast before. The guy at my boat storage place had me try a 17 inch prop and it was WAY to easy to get my RPM's high so, I switched to a 19 inch.

Anyway, I dont want to go into too much detail until I have all the facts straight. So, my question is.. When testing WOT, do I just gun the boat and see how fast I get it to go? And of course, if the rpm's can go above what is safe, does that mean I really SHOULD change the prop? Does a good prop not allow your engine to go over the max RPM?

Thanks,

Flingus

 

[642mx]

Re: WOT Question

It depends on your set-up. Most any EFI Mercruiser will hit a rev-limiter before you can do any damage. My carbed Mercruiser doesn't and I've had it past the recommended max rpm testing props.

What engine do you have?

 

[flingus]

Re: WOT Question

Running it near the limiter even makes me nervous.

I have a volvo penta, 5.0 liter I believe. Its a 2000 Larson Cabrio, 22 foot.

I think the max rpm is 5000 but, I'm not positive. I have a sticker on my tach that gives me the max range though.

 

[cribber]

Re: WOT Question

Max rpm is 5000 if you have the Penta 5.0 GXi

http://www.boattest.com/engines/230016/overview.aspx

If you start heading north of that then it's time to back off the throttle.

 

[hwsiii]

Re: WOT Question

flingus, after you get the motor to WOT then use your trim button to trim the out drive up until you hear the prop ventilate and then just touch the trim down until it quits ventilating, and that should be your maximum speed.



H

 

[flingus]

Re: WOT Question

Well, my real question is..

Do I need a new prop, if I'm able to go over 5000 rpm with my current prop? Should I be able to go over my max? I know I shouldn't, but my question is if I can reach over 5000, does that mean I need to change props?

And so WOT is basicly just running the boat as fast as I can, up to my max rpm?

Thanks everyone!

 

[hwsiii]

Re: WOT Question

flingus, you should not be able to over your WOT RPM with the right prop, you are right.



H

 

[flingus]

Re: WOT Question

Ok. Well, I'll see how fast she'll run tomorrow. I think the prop I have on it now, is the same as the one that came with the boat when it was bought new so it shouldn't be too bad. At this point, the boat runs well but, I just want to make sure I have it as efficient as possible.

In my opinion, which is not much.. I think I'll be able to reach 5,000 rpm very easily, and beyond. We'll see though.

Thanks again !

 

[QC]

Re: WOT Question

do I just gun the boat and see how fast I get it to go?

I just want to clarify something as a couple of your questions could be misinterpreted. You do NOT have to mash the throttle from a stand still. You can leisurely get her on plane, safely make sure there is nobody in your way. Play with trim and stuff and then make a final portion of your run at WOT (throttle handle all of the way forward). You need a little time (you mentioned 30 seconds which would be good) to make sure you are getting all of you can out of her. A little overspeed to say 5200 won't kill her dead, but you need to see what the best you can do is, with a typical load and trimmed as fast as you can get her to go. Of course if she is quickly and easily revving past 5000, then you are pretty seriously underpropped and you won't even be able to give us good data to work from until you get her a little closer to right.

Oh, oh, make sure your tach is right

Edit: There was a GL (220) and a GI (2540) 5.0 then. The GL was rated 4400 - 4800, and the GI 4600 - 5000. I don't believe the GXi was was out yet.

 

[flingus]

Re: WOT Question

Safely make sure no one is in my way? What fun is that?

Nah, I read you loud and clear. Get her on plane, make sure I have a good amount of room in front of me, and see what happens when I have the throttle all the way forward. I'm on a pretty big lake, and I plan on going out tomorrow instead of during the weekend so, should be a good time to test out the boat.

My gauges seem to be fairly accurate. Speedometer even matched up with GPS, at the most there was maybe 1 or 2 mph difference.

Best forum ever!

 

[flingus]

Re: WOT Question

Thanks again to everyone for the advise. I'm not worried about the prop, not sure why the marina I keep the boat at wanted me to move to a 17 inch. I can't imagine getting much better performance.

Went out on the lake, kicked it up to WOT and hit 45 mph at 5,000 RPM. Honestly, I don't think I want to go faster than that. This was with two people on the boat, and a full tank of gas. (60 gallons) I might try a fancier performance prop next year but, this prop seems more than safe, and has good performance.

Flingus

 

[180shabah]

Re: WOT Question

sounds like your in a good place as is.