Questions for the 3.0 140hp owners

[cheetah90]

Im going through some prop swapping to see what works the best on my boat, i know every boat is different but i was curious what prop worked best for your 3.0 setup? so i have a few questions.....

What prop you running?

Model/size/year of your boat?

Whats your w.o.t rpm?

Whats your top speed?


Thanks Guys!

 

[steelespike]

Re: Questions for the 3.0 140hp owners

I guess thats one way to do it but there is a lot of prop experience here.
The likelyhood of finding the exact setup is pretty slim.
If you tell us about your boat,your present prop size and max rpm and speed.
(light load)Typical activities,and load.The guys here can get you setup.

 

[cheetah90]

Re: Questions for the 3.0 140hp owners

I guess thats one way to do it but there is a lot of prop experience here.
The likelyhood of finding the exact setup is pretty slim.
If you tell us about your boat,your present prop size and max rpm and speed.
(light load)Typical activities,and load.The guys here can get you setup.

Ok thanks! well this weekend i wrote down a couple things.

Boat is... 1990 Cheetah 1700 open bow net weight of 1870lbs...powered 3.0 alpha 1 drive, 15 gallon fuel tank, i dont carry much gear, small tool box 20lbs "i weighed it" Anchor 15lbs. misc gear life jackets ect ect im guessing another 20 to 30lbs or so.

This weekend the lake was pretty calm so i did a WOT run with just me and the soon to be wife weighing in at a whopping 106lbs and me weighing 185lbs,
cooler 12pk bag of ice,the day before i ran the boat on E so on the way to the lake i stopped and put 5 gallon exactly.

currant prop is 14.5 19p aluminum, WOT i was at 4700 rpm and 32/33 mph that was on speedo forgot gps but i have checked the speedo before with my gps to see how accurately it works and it was pretty close was or 3mph faster than the gps speed. i trimmed up slow until it started to porpus
than back down a little my rpm was almost 5000 with little change speed. i dont pull tubes or skiers just cruise/fish and never have more than 4 people in the boat i would like to find a prop that would give me a little more top speed.

What do you think? is that enough info if not let me know? Thanks!

 

[steelespike]

Re: Questions for the 3.0 140hp owners

Something isn't right.a 19" prop at 4700 to 5,000 should be pressing 40 pretty hard.
If the tach is right you have a lot of slip going on.Is the prop in good shape?

 

[cheetah90]

Re: Questions for the 3.0 140hp owners

Something isn't right.a 19" prop at 4700 to 5,000 should be pressing 40 pretty hard.
If the tach is right you have a lot of slip going on.Is the prop in good shape?

The prop is in great shape only about a month old no dings or scratches etc.As for the tach seem to be working correctly. Prop slip?? not sure i know its tight and i torqued it to spec. how do i check the prop slip?

 

[45Auto]

Re: Questions for the 3.0 140hp owners

Prop slip doesn't mean that your prop is slipping on the shaft.

It's how much the prop slips in relationship to the water. Your 19" pitch prop should theoretically push your boat 19" forward every time it goes around. In the real world, it will only push you 18" or so every time it goes around. This means it "slips" 1 inch out of every 19 inches it should be going, so it has a "slip" of 1/19 or about 5%.

You can see your slip by putting your numbers in here a prop slip calculator on the internet like this Mercury one:

http://www.mercuryracing.com/propellers/propslipcalculator.php

To use the Mercury one, enter any 4 numbers then hit "CALCULATE" under the remaining one to find it. For example, your pitch is 19, your gear ratio is 2 (if it's the original outdrive), your engine RPM is 4700, and your speed is 33. Put those numbers in the calculator and you will find that your slip is 22%

Some people will spend hundreds of dollars trying to get their slip as low as possible. If you want to see what a prop with less slip would do in your case, remove the 33 from the speed block. Put 5 in the slip block and hit "CALCULATE" below the speed. It will show you that with 5% slip your boat would go 40 MPH. However, that's only real if your boat has the power to turn the prop with 5% slip at the same RPM.

 

[cheetah90]

Re: Questions for the 3.0 140hp owners

Hey Thanks for the Info!!! Im going to read into this prop slip stuff