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Definition of "Wide Open Throttle"
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Author:  mspitz [ Fri Mar 19, 2010 4:11 pm ]
Post subject:  Definition of "Wide Open Throttle"
Can someone define the meaning of "Wide Open Throttle" (WOT)?
Author:  mspitz [ Fri Mar 19, 2010 4:48 pm ]
Post subject:  Re: Definition of "Wide Open Throttle"
I guess that I need to clarify myself on why I am asking the question.

I currently have a 95' Horizon 200 with a 190hp 5.0L. I believe that the WOT is 4200rpm with a gear ratio of 1.66. My family uses the boat for wakeboarding at speeds of 18mph to 24mph. We occassionaly slalom at 25 to 29mph (all according to the boats gauge).

I currently have an Apollo 3 blade, SS, 17 pitch, 14-1/4" diameter prop. I feel that the prop size is good whenever wakeboarding, but a 250 lbs slalom skier drags in the water for quite some time.

The boat rpm when wakeboarding is approximately 3,000 to 3,400 rpm but getting around the 4,000 rpm range whenever slalom skiing.

I am interested in trying a 4 bladed prop (due to literature about the stability at lower speeds), probably an 18 pitch and 14-1/8th diameter. My concerns are:

1: Hurting my holeshot for the slalom skier
2: Being under the WOT rating for the motor whenever pulling maximum loads

Any thoughts would be appreciated.
Author:  cougarcruiser [ Fri Mar 19, 2010 4:52 pm ]
Post subject:  Re: Definition of "Wide Open Throttle"
Image
Author:  jsimon [ Fri Mar 19, 2010 5:29 pm ]
Post subject:  Re: Definition of "Wide Open Throttle"
WOT as I know it is defined by "under any and all load conditions, the WOT rpm is NEVER exceeded." You need to have enough prop on to load the engine enough as not to exceed the WOT
Author:  Aussie_Horizon_190 [ Fri Mar 19, 2010 7:14 pm ]
Post subject:  Re: Definition of "Wide Open Throttle"
Definition of Wide Open Throttle - look down the carb and the butterflies will be dead vertical offering the least airflow resistance (hence the 'Wide Open'), therefore delivering maximum airflow into the engine and maximum power.

Often worth checking this (engine not running of course!) to see that full throttle on your control translates to vertical butterflies. I dunno how many times I have seen on road cars (and some race cars) where the accelerator is floored and the butterflies are not fully open!
Author:  07H200SS [ Fri Mar 19, 2010 8:28 pm ]
Post subject:  Re: Definition of "Wide Open Throttle"
The 4-blade prop will definately make for a better hole shot. I run a Mercury Rev4 prop (4-blade) and gets my boat out of the hole quick.
Author:  DaleG [ Tue Mar 23, 2010 12:24 pm ]
Post subject:  Re: Definition of "Wide Open Throttle"
You can run a prop with lower pitch (a smaller number) which will give you a better holeshot. However, you do run the risk of overreving the engine. You would now have to pull the handle back a bit in order to not overrev. the top speed would be lower. I did this on a previous boat and had one prop (a 21 pitch) if we were going to do extensive cruising, and a different one (a 19 pitch) if we were going to waterski all weekend. Four bladed props tend to have a better holeshot at the expense of top end. The increased blade area helps at startup but hurts due to increased drag on the top end. Props are different so you need to try it first before buying if at all possible.
Author:  mspitz [ Fri Mar 26, 2010 1:05 pm ]
Post subject:  Re: Definition of "Wide Open Throttle"
Thanks for all of the help.

Is is common for a marine shop to let you try different props before purchasing?
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