Prop Selection Question

[Andy]

I recently bought a 1989 Eluder w/ a Mariner 175 "Ski". The previous owner had a Bob's nosecone and Low water intake installed and had the motor "dry stacked".(It is noisy!) It has a 24" LaserII prop and a manual jack plate with a 6" set back. The Jack plate is set so the foot of the motor is about 3" below the transom.

With a full tank of gas (35 gals) and my 135 lb teenager driving, it will indicate about 62 mph ( this is with a pitot speedo, not GPS or radar) and the tach is indicating about 65-6700 rpms. I say about, because the tach only goes to 6,000, so I am "guesstimating" the RPM's.

I have never set up a boat before, but from what I've read on the internet, it appears that I should be running a prop with a longer pitch. Does anyone know the recommended max RPM for this motor? Any recommendations on what type of prop and what pitch? Any recommendations on a prop shop that has a good exchange program?

Any other recommendations? Should I start some where other than the prop?

Thanks for your time and advice.

[Andy]

I recently bought a 1989 Eluder w/ a Mariner 175 "Ski". The previous owner had a Bob's nosecone and Low water intake installed and had the motor "dry stacked".(It is noisy!) It has a 24" LaserII prop and a manual jack plate with a 6" set back. The Jack plate is set so the foot of the motor is about 3" below the transom.

With a full tank of gas (35 gals) and my 135 lb teenager driving, it will indicate about 62 mph ( this is with a pitot speedo, not GPS or radar) and the tach is indicating about 65-6700 rpms. I say about, because the tach only goes to 6,000, so I am "guesstimating" the RPM's.

I have never set up a boat before, but from what I've read on the internet, it appears that I should be running a prop with a longer pitch. Does anyone know the recommended max RPM for this motor? Any recommendations on what type of prop and what pitch? Any recommendations on a prop shop that has a good exchange program?

Any other recommendations? Should I start some where other than the prop?

Thanks for your time and advice.

[Chris]

Welcome to the board Andy! http://www.checkmate-boats.com/infopop/emoticons/icon_smile.gif

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[Bill]

Welcome to the board! You did not state which part of the gear case is 3 inches below the pad, it should be the center point of the prop shaft. The nose cone has to go, that is slowing you down. You should have your tach checked for accuracy too, you should definately not be running those high of RPM's with a stock motor. Check with your local Mercury dealers as far as swapping props, They should have some you can try with a deposit before buying so you get the right one.

2003 ZT 240 6.2litre/Bravo 320 H.P. 25P Mirage Plus

[Andy]

Bill,
Thanks for your advice. I'll look into having the tach checked. The center line of the prope shaft is what is about three inches below the bottom of the transom. The local Mercury Dealer here doesn't lend out props, unfortunately, so I may have to do that by mail. I was curious about your comment on the Bob's Machine Shop nose cone. Several articles that I've read on the internet are complementary of the units, especially regarding top speed and control. From the looks of it, it would require replacing the entire foot to get rid of it and the low water intake. What would you recommend in its place?
thanks again for your insight.
Andy
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Bill:
Welcome to the board! You did not state which part of the gear case is 3 inches below the pad, it should be the center point of the prop shaft. The nose cone has to go, that is slowing you down. You should have your tach checked for accuracy too, you should definately not be running those high of RPM's with a stock motor. Check with your local Mercury dealers as far as swapping props, They should have some you can try with a deposit before buying so you get the right one.

2003 ZT 240 6.2litre/Bravo 320 H.P. 25P Mirage Plus<HR></BLOCKQUOTE>

[Bill]

The nose cone only helps above about 82-83 mph. If anyone says good things about them well below that are probably advertisers. I am surprised to here that you local merc dealer does not do the "loaner" program, Mercury pushes pretty hard for dealers to do that. Mercury even provides props to dealers at a discount at times for DEMO use. Where your prop shaft is now is a good starting point. Somthing sounds off as far as the rpm,s. You are spinning too much fo that size prop in relation to the height of the motor. If the prop damaged at all?. Do not get me wrong on the nose cone, if you have the right set up, they are great, just not for your set up. The stock gear case would be much better.

2003 ZT 240 6.2litre/Bravo 320 H.P. 25P Mirage Plus