Question about WOT?

[MrDumb]

I have always wondered when manufactures say what your motor is rated at WOT, if that is a point that you should not go past. Also is it really OK to run your motor at or close to WOT for extended periods of time or just temporaily? What I am getting at is I was thinking of propping my boat to run at a lower RPM for cruising ( maybe around 3600rpm). Or will that be more damaging to a motor. I dont know just thinking here????

 

[Walt T]

Re: Question about WOT?

It is not recommended to run any engine at wot for extended periods.

 

[MrDumb]

Re: Question about WOT?

OK but what about running below WOT at a lower rpm where you are lugging the motor more?

 

[rattana]

Re: Question about WOT?

You should prop your boat so that it will acheive WOT. Then you can cruise at lower RPM's without damaging your motor. If you prop it so your WOT is below recommended RPM you will lug your motor. Lugging is never good for your motor. You will have poor fuel economy and not have enough power to handle swells. It will take longer to get up on plane. That is just my experience.

 

[MrDumb]

Re: Question about WOT?

I have a 1992 3.0 OMC Cobra WOT is 4400rpm. What is a level of rpms that would be considered to low to at for cruising?

 

[salty87]

Re: Question about WOT?

are you talking about re-propping for lower rpm's or just cruising?<br /><br />if just cruising, then whatever speed your boat gets on plane is usually the slowest you can go. well, you can go slower but that's definitely not 'cruising'. you'll usually be more comfortable and put less stress on the engine by going a bit faster. the conditions you're boating in will dictate that to some extent.<br /><br />if you're talking about re-propping, the generally accepted method is to prop the boat to achieve WOT. that will give you the best performance and be the most economical. you don't have to cruise at WOT though.

 

[MrDumb]

Re: Question about WOT?

I have a 15x17 aluminum on it now but would like to go to a 19 pitch to lower my rpms to cruise at a faster speed around 30mph is what I normally cruise at. It would probaly turn easier too?

 

[rattana]

Re: Question about WOT?

When you are crusing at 30 MPH, what is your RPM?

 

[navigator336]

Re: Question about WOT?

If I understand correctly, you want to cruise at 30 mph but do it turning fewer rpm's and achieve that condition by running a 19" pitch prop in place of your current 17". If your WOT is 4400, which is the low end of acceptable, with your current 17" prop, you'll be hating life if you go to a 19. You'll be at lower rpm's at 30 mph, but you'll be burning alot more fuel doing it. In addition, you'll really be working your engine hard. Try trim tabs instead.

 

[mercrewser]

Re: Question about WOT?

Trim tabs wont help in that application, they lower the planing speed. Leave that set up alone. If you want to cruise at 30 with a lower RPM, you need more power. Dont over prop the boat, 2" of pitch on a 4 banger will make to much of a difference, especially getting up out of your own way on to plane.

 

[akriverrat]

Re: Question about WOT?

what it boils down to is that a change of prop is not going to yield the result you are after. it is just going to abuse the engine. the only thing that will get you where you want to go is more horse power or less weight in the boat.

 

[MrDumb]

Re: Question about WOT?

I do not understand why would you be doing more damage to the motor if you can run it at a lower rpm? Loaded down I can cruise at 30mph @ 4000 rpm, but if I had a 19 pitch I could do it at 3600rpm? I think it would be easier on the motor. Please explain.

 

[Bondo]

Re: Question about WOT?

Any time a motor Lacks the Ability (Horsepower) to Reach the Recommended WOT RPMs.......<br />It's Lugging .......<br />Lugging the motor will Kill it, Much quicker than an occasional over-rev......<br /><br />With a Properly Propped boat,<br />WOT might be 4400/4600RPMs........<br />The Most Efficient RPMs will be around 3200/3500RPMs..........<br />Whatever your MPH is at this RPM, will be YOUR Cruise Speed.........<br /><br />But, Hey, It's Your Boat......<br />You can do Anything You Please.......<br />And, When you Burn a Hole in the top of your Pistons,<br />You can come back here,<br />And Tell Us About It..................

 

[MrDumb]

Re: Question about WOT?

So do you think that if I went to 14.25X19 3 blade aluminum (probaly a Hustler) that I would not be able to reach WOT?

 

[Bondo]

Re: Question about WOT?

You have Yet to state What your RPMs are at WOT......<br /><br />If you're at 4400RPMs with the 17",<br />You'll Never be able to pull 4400RPMs with a 19".......<br />There for, You'll be Lugging your motor.......

 

[MrDumb]

Re: Question about WOT?

I can hit 4500 rpms now with that prop.

 

[mercrewser]

Re: Question about WOT?

put the 19 on it and try it. Your not gonna like it. With 4 people and full gas try to plane it and see what happens. Revs should be -4000 with the 19, below MerCruiser specs.

 

[MrDumb]

Re: Question about WOT?

My motor is a 3.0l OMC with a Cobra outdrive. Would the decrease in diameter make any difference , going from my current 15" to a 14" ? I really apperciate all of you guys help.

 

[akriverrat]

Re: Question about WOT?

4500 with 17" will be about 4300 with 19" (if you are lucky). you will be under the recomended wot for that engine. lugging the motor. you are not going to solve the overweight/underpowered problem this way. how many ways by how many people and how many times said befor you get it.

 

[Bondo]

Re: Question about WOT?

How many Ways, by how many People, and how many Times said,<br /> Before you get It.

Yep.......<br /><br />You've Got the Right Prop NOW.................