No such thing as a stupid question?

[Plan J]

Hi, Plan J is a 1980 F-253 with a 318, velvet drive and lots of love. I have read that my "starter" prop should be a 14x10 cupped, and I am pretty sure that is what is on her. I am wet on Lake Minnetonka for the season and would like to idle her around 800rpm, currently sits at 1800 closed throttle, what pitch should I be aiming for to achieve an 800rpm idle and is this advisable? We have come to terms with the fact that this is not a speed-boat, also not likely to see any other water than Minnetonka.

Cheers!

[srokag44]

Sounds like you need to adjust the carburetor before considering changing the prop. With the transmission in neutral, it doesn't matter what prop is on! What is your rpm at idle in neutral? Have you adjusted the throttle linkage?

[BobCT]

The general way props are "sized" to the boat is at wide open throttle (WOT). The idle speed is determined by the engine idle. So, for now simply adjust the carb idle stop to 800 rpm's and you should be set.

1,800 is way too high and will kill your transmission if you're shifting in/out of gear that high.

Bob

[Plan J]

OK, so the neutral idle is running 1500, i am suspecting a bad tach since it sounds closer to 700 to me, reading 1800...In gear it runs 1950 (acording to the tach). Sounds pretty close to that but let me get a reliable reading and I will reply to this thread.

I am able to run her down to about 500 with idle mixture adjustmensts so I think the carb is good to go, just curious about how radical I can go with the prop pitch.

[Plan J]

Also need to point out the fact that at 1800 RPM idle, the speed of the boat is perfect, minimum wake, perfect.

[prowlersfish]

You have 2 separate issues .

Idle
If you really have a 1800 RPM idle you will do damage to the transmission when putting it in gear. The idle should be in the approx 600-700 rpm range . All this has nothing to do with the prop .


The Prop .
14 X 10 is a good starting point . To tell if the prop is right you need the boat bottom to be clean along with the prop and running gear .nd the engine is running right . Then take the boat out and when it is safe to do so run it at full throttle . You should be able to turn around 4000 RPM at throttle


But before you can do anything you need a good tachometer

[captainmaniac]

Get a separate tach to check it out. As a simple test - how fast is the boat moving when in gear at idle? If 3-4 knots max, you are probably idling around 800 or less, and your tach is off. If you really are idling at 1500-1800, you will be doing 8-9 knots and throwing enough wake that everyone in the marina is screaming at you, and your idle or throttle detent screws need adjusted.

[Commissionpoint]

I have 2 seperate boats. Thats probably not only not the same issue, but not on topic either. All that aside, I'm interested in trying a 14*10/11 RH on the Nautique if anyone want to ditch one.

[Plan J]

OK, thanks for the replies, the stock tachometer was my biggest problem. She is now neutral idle at about 750, in gear idle close to 600, seems happy if not a little slow but that is fine with me. I am only getting about 3500 on the big end with a clean bottom, tabs etc...Prop is a bit chewed up from the previous owner (missing about 1/2 inch on the ends), regardless, we will be good for the short remainder of the season this year and will have the prop re-worked over the winter.

Thanks again!