prop pitch and size reccomendations

[wavrider]

17 foot skeeter bass boat, cmc tilt n trim, set back around 5 inches. 85 hp rude 1973

I can not read the part number on the prop, it is just gone, turning around 4000 wot throttle now, new tach.

any reccomedations on size and pitch would be appreciated, thanks

 

[walleyehed]

Re: prop pitch and size reccomendations

First, is this tach an OMC/BRP? If so, is it set on 6?
We need to make sure the tach is right, because if it is, that engine ain't got much time left running at 4000RPM WOT.

 

[wavrider]

Re: prop pitch and size reccomendations

Brand new fairo tach. set at 6 pole,

Second time I had boat out, first time with new tach, engine and boat combo is new set up.

Purchased hull separate from the engine so just starting the set up.

Thanks

 

[steelespike]

Re: prop pitch and size reccomendations

Not knowing the prop size is a problem.Also would be good the have the GPS speed.Assuming the motor is in good shape and properly tuned I think you need to address the setup.Start with the antivent plate(just above the prop)even with the bottom of the boat.raise the motor a hole at a time until just before venting becomes a problem.Be sure it pumps water.Be sure to carefully adjust the trim.Let us know what you get.
It would be good if the dealer lets you try some props.If you intend to buy
they usually will.I think the Skeeter is a fast boat my guess is a prop in the 17 to 19" pitch range.You may be able to have a prop shop check the pitch of your prop.

 

[Silvertip]

Re: prop pitch and size reccomendations

Since this is a new setup, I would also check to make sure the butterflies in the carb are opening fully (perfectly horizontal in the carb bore). If not, that would be the reason (or one of them at least) that you can only get to 4000 rpm.

 

[wavrider]

Re: prop pitch and size reccomendations

I will check it out again this weekend, had ignition issues, got them resolved and lets see what the rpm's look like next time out.

Gps is in the mail hope to have it by this weekend for more accurate readings as far as speed. thanks for the replies.

 

[walleyehed]

Re: prop pitch and size reccomendations

6 is not the correct setting for the Faria tach....
I'll have to check and see what it should be....it's different than OMC or Teleflex.

 

[wavrider]

Re: prop pitch and size reccomendations

4 is the setting for the fairo tach, according to instructions i recieved with tach. this is the second one I installed, first on the bayliner, both appear to be working fine, thanks

 

[walleyehed]

Re: prop pitch and size reccomendations

In one of your above posts, you mentioned it was set on 6. Is it NOW set at 4? Or, are you showing the 4000 on setting #4?
I guess my point is that, if this engine is really turning 4000rpm at WOT, you got a major problem that will destroy the engine if left that way......at 4000RPM, the plates should be only half open...if 4k is all you get at full bore, plates 90 degrees, the engine is going to self-destruct.

 

[wavrider]

Re: prop pitch and size reccomendations

fixed the ignition problem, sort of, still a smal miss intermittently at idle but only every now and then, that is another issue.

Tested it today, I raised the engine up 3 notches where the cavitation plate is even with the step on the transom, not even with the bottom of the boat.

Hitting on all 4 cylinders, new tach, got 5500 WOT, can trim out to 5800 before starting to blow out, speed on gps is 30 mph. speed on speedometer on boat says 31 so basically accurate.

Last time out had 35 or 37 with the speedometer on boat, did not have gps then,at 4000 rpm with ignition problems.

I think I may have the engine to high as when i go to turn I blow out if above 4000 rpm, going to lower the engine a hole and see what happens. thanks and still no numbers on the prop to know what I am working with, I do have a few other props to fit on it so I may change it out just to get a base line tach reading from a known size and pitch prop.

 

[walleyehed]

Re: prop pitch and size reccomendations

If you will take the time to make one change at a time, such as moving only one mounting hole at a time, and stay with one "KNOWN" prop, you can evaluate what is going on. If you change more than one thing each time, you'll never know what part made the difference.
On the boat speedo, they can change from 1 run to the next, and I would recommend you never use "it" for data...just the tubing getting a pin-hole or getting dry can change the reading and as a rule of thumb, they most always read high.

 

[wavrider]

Re: prop pitch and size reccomendations

thanks Wallyeyed for the reply.

hopefully get it straightened out this weekend if weather permits

 

[wavrider]

Re: prop pitch and size reccomendations

Got the ignition straightened out, runs great so no issues there.

Lowered the engine one hole, 5500 WOT, 31.5 on the GPS. Two passengers 390lbs, 11 gal of gas, two batteries, trolling motor mounted in front.
Best hole shot so far, (could be cuz ignition is correct).
With son in the bow, will jump on plane in just a few seconds and hit max speed quickly, with son on seat beside me nose wants to come up a little higher of course but still jumps on plane quick and accelerates fine.

Can use cmc t-n-t and start ventilating after tilting engine up just a few degrees.

with engine trimmed just before vent occurs I can turn pretty sharp, not cutting hard but a good sharp turn and prop does not vent in the turn.


does 31.5 mph sound correct with this set up and a 35 year old 85hp engine?
I am satisfied with the performance just want to make sure it is set up correctly to get all the life out of that old rude that I can. thanks for the replies

 

[steelespike]

Re: prop pitch and size reccomendations

Not knowing the weight of the boat or prop its difficult to be accurate but
seems a little slow to me seems like 35 to 37 would be more accurate.
Seems like your setup is pretty close for that prop a better prop might give you one more hole up and more push.

 

[wavrider]

Re: prop pitch and size reccomendations

The hull is a skeeter starfire, I believe nada says it is 1090 lbs.

The old 1973 rude is runnig as good as she can, tuned lync sync etc etc

I was able to get 33 out of her one hole up but she was wanting to vent on the turns so, yes I can not read the numbers on the prop on it now, bad thing.

I do have some props that I know what they are so if I get ready to experiment I will start all over again with a known size and pitch prop.

thanks for the replies

 

[steelespike]

Re: prop pitch and size reccomendations

That's probably a good plan.I feel that you have your motor tuned well and I assume you have good compression. I think with a stainless prop and the set up fine tuned you will be in the 35 to 37 range possibly more.A stainless prop should give you that notch back and just the notch could give a couple of mph.and the prop a little more.
I checked a bunch of 75 hp setups and they all ran over 35.In good shape your 85 should be making at least 80 at the prop.Keep in mind even if your not interested in top speed getting her to that point will help your mileage.