As the subject says, bought a 97 18' Astro with a 92 Merc 150hp 3 blade 19 pitch prop (not sure of brand).

With about 450lbs of people and full tank of gas i got 53mph @6,000rpm on the gps. Comes on plane at about 3,000, I would have thought a little faster top end. Does this sound right?

Thanks

what kind of speedometer are you using? If you are using a water pressure type it could be way off. Use a GPS.

Your RPMs seem to be in the right range. SO you seem to be propped right.

With a 19 pitch prop, that is not bad. If you want a little more speed, you might want to try a 21P tempest plus.

It will give you a couple more mph, and reduce you WOT to 5700. If you are concerned about speed, try to keep your boat as light as possible...1/2 tank of gas, skinnier friends...remove the tackle suitcases..etc.

Sounds about right to me. All those 60mph 150 hp boats are few and far between when you put the real killer of mph (GPS) to them.

Since you did post performance figures based on GPS, I would guess you are under propped unless the boat was used for pulling water skiers.  A higher pitch should improve top end. That boat is quite bulky and the hole shot will be slower with a higher pitch prop.

 

I have an 89 Astro 18FDX with a 150 Merc and might get 55mph on the gps. With no tackle and a short fuel load, one person I got 63mph - radar gun - when the boat was new. I don't recall the rpm's.

I hope you have as much good luck with yours as I have with mine. It has just been a super boat and still is picture pretty.

I have an 18.5 ft champion with a 150 hp erude on the back.  I run 23 and 24p props and can get 58.6 gps at 5800.  Red line for my motor is 5500.  You might want to check yours before consistent 6000 rpm runs.  I would say you are definitely under pitched.  I would run 23 at a min and try a 24.  Do you have a jackplate?

I put the mph killer (GPS) to my '97 185 procraft with '97 150 efi merc and it showed 62.1 mph with 2 people, 1 tank fuel and empty livewells. It has a 23p prop running 5900 rpm.

We have a 97 astro fish and ski 18 foot with a 175 and go around 55-60.  If i am by myself it will hit 60 tops.

Thanks to all for the input.  I do not have a jackplate.  Had suggestions from a 21 to a 24 but, most have said it runs good, leave it alone. 

Going to wait unti spring to decide. 

Thanks again

I would definitly investigate a little more.  I would almost guess that your 19p prop has been worked to a higher pitch or your tach is off.  One or the other.  I would want to nail that down, otherwise you could run the risk of over revving your engine.  I am not an expert by any means but, from what I have read, a 150 would spin a 19p prop too fast.

I have a couple of prop dings that I need to get worked when I put it up for the winter (coming MUCH too soon). 

I talked to a local Merc mechanic and he said the motor should spin 6k all day.  He added that he might try a 21p if he could get one cheap otherwise he would leave it alone.

Think I'm going to start watching ebay and see if I can pick up something cheap.

Thanks again for all the help.

I have a 1987 Ranger 373 with a 87 150 Mercury Black Max mounted on a 6" jack plate. With a little bit of chop on the water, 1/2 tank of gas, 1 full live well, 300 lb driver, tackle suitcase, she will run 62-63 mph on the GPS (65 on the speedo) into the wind using a 22P Michigan wheel 4 blade prop at 6000 rpm.

With the same set up, and 2 people, she will run 57-58

I tried a 19P prop on my merc 150 when I had it mounted to 17' procraft fish and ski. I punched the gas up to wide open throttle(awesome hole shot). After a few seconds, I glanced down at the tach and my eyeballs almost popped out of head. I was turning 6800 rpm! I backed down to 5800 rpm's immediately. The motor was smooth, powerful and sounded pretty cool.

Needless to say, I switched to a 23P for that boat.