Not enough Prop!

[trxxx250r]

Hi,

I have a 19.5 ft Stratos (219DC) bass boat with a 1995 Johnson 175 Fast Strike (j175gleom). Boat and motor weight approximately 1700 lbs. per factory spec. I'm 200 lbs.

I bought it used and it came with a flawless stainless "Shooter" prop (13.5 x 23). It works fine but here's the deal.

I trim all the way down and come out of the hole fine (at least it seems from my limited experience). I trim up immediately and it screams. It GPS's at 59-60 MPH at optimal trim with no weight on the boat other than my 200 lbs.

It cruises 45 MPH @5500 RPM.

Here's the problem, when I open it up and trim it out, I'm hitting 7k RPM. That's exceeding the factory recommended top RPM by 1200 RPM. It seems to me the motor is putting out too much power for this prop thus not keeping the motor in it's optimum operating range.

Anyway, this is my experience and I'm looking for advise on what to do. I've been into racing motocross and quads on land with both 2 and 4 stroke motors and I know when the motor is running out of gears or in this case, prop... Maybe I'm wrong.

Please help! It will be much appreciated!

 

[steelespike]

Re: Not enough Prop!

I suspect your tach is reading high.If we assume 13% slip 1.89 ratio 7000 rpm would produce about 71 mph.
You need to verify the tach,perhaps borrow a shop tach.If we assume 60 mph at 13% slip we get about 5800 rpm.

 

[jestor68]

Re: Not enough Prop!

A 1.86 ratio turning 23 pitch using a reasonable 9% slip at actual 59 mph works out to about 5551 rpm.

I think your rpm range is 4500-5500.

I agree that it looks like your tachometer is way off.

You might try removing the connector and cleaning the pins. This sometimes restores proper readings.

I would verify the accuracy of the tach; then step up to the next pitch size(according to whatever prop you're using, it may be one or two inches).

It should be noted that the Shooter is old technology 4 blade hole shot type prop.

If you want to kick it for top speed, consider a Raker II or Fury 3 blade prop.

 

[trxxx250r]

Re: Not enough Prop!

Good info, thank you! It did cross my mind that the tach could be off. The boat sat in the sun for years uncovered. Actually the next thing I was going to buy for the boat was a speedo and a tach. So, maybe I will wait to get that before I make a big mistake with a wrong prop. I have heard bad things about the shooter and good things about the raker. I just want to be sure exactly which one I need.

Jestor - I'm glad you mentioned the holeshot/top speed thing. Actually top speed is secondary, I would rather get up on plane quicker. Plus, I pull skiers/boarders and tubes from time to time so it can't be a dog out of the hole. That said I would love to go faster. So, I need a prop that will be strong out of the hole but still give me good top speed. I guess that's the challenge, right? What prop would fit that bill?

 

[jestor68]

Re: Not enough Prop!

It sounds like a 4 blade is the better choice for your intended uses.

The Renegade Bass(BRP) might be considered the contemporary version of the original Shooter. It comes in the same size.

My Mercury prop choice would be the Trophy Plus 4 blade. It might have a bit more performance due to it's larger(13.75") diameter. Since it comes in a bunch of pitches(21-29), it would be easy to find to exact pitch to dial it in.

 

[Faztbullet]

Re: Not enough Prop!

Also got to remember that pack is RPM limited @ 6100....

 

[trxxx250r]

Re: Not enough Prop!

Ok, let me get a new tach installed so I can be certain of where my motor is and then I will repost with data and my requirements and hopefully come up with the perfect prop for my needs.

Thanks for all the help so far! I would have been headed for a big PITA lol.