first post guys!

[87 caravelle]

first time boat owner and im 27! i do love my first boat, its a 87 glasstream 182 caravelle. good shape in and out good motor, thats all i need and the money was right. btw i did forget the plug the first time sooo.... any way it has the 3.0 merc w/ an alpha one. my question is what would you think the top speed is for the boat? it has a 15 x 17 aluminum prop and the motor has been tuned up and runs great, but i dont know the hours. the speedo says 33-34 mph when i hit the sweet spot w/ the outdrive and thats on a lake as smooth as glass. the boat JUMPS out of the water and gets on plane in about 2 seconds, which i like, but i wouldnt mind trading a little low end for top end. so does that sound right, 33- 34 mph for this set up? and if i want more top speed, say 40 mph what should i get for a prop? btw w.o.t goes to 5200 rpm but the side of the motor says max w.o.t for the motor is 4200-4600 rpm if it helps at all. thanks guys and sorry for any confusion i suck at explaining myself.....so the ol lady says

 

[Muqwump]

Re: first post guys!

Not sure for that set up what the top speed should be but what are you trying to do? Are you trying to pull someone?

 

[rndn]

Re: first post guys!

Welcome to the forum!!
If you are indeed running over the max rpm's, you need to change prop pitch. It is usually 200 rpm's up or down for each inch of prop change. If you're running 5200 and need to drop to 4600 and running a 17" prop you need to run a 20" pitch or maybe a 21" pitch. You may want to try a four blade as going up 4 inches will hurt your hole shot.
By the way, you explained yourself just fine.

 

[rndn]

Re: first post guys!

Feel free to ask any and all questions as there are many boaters with years of experience on this forum always willing to offer up their knowledge. If you do end up getting a new prop, keep the old one as a spare in case you hit something with your new prop.

 

[rndn]

Re: first post guys!

After looking at NADA, your boat weighs 1950# so with the 3.0 , I'm suprised you are able to over rev a 17" prop by 600 rpm's and 21" sounds like a lot of pitch for a 120hp 3.0 liter and a 1950# boat. Are you sure your tach is accurate?

 

[steelespike]

Re: first post guys!

First thing you can run that prop but don't exceed the 4,600 max rpm.
A 19 will put you at about 4,800 and a 21 about 4,400.
About 200 rpm for each inch change.Each will take more out of your hole shot.If you ski or carry lots of people/weight you may like the 19 just don't over rev.The 21 will probably produce the most speed and you could change to the 17 for skiing etc.

 

[87 caravelle]

Re: first post guys!

i see. so changing to a 19 or 20 should also increase gas mileage...ya know, seeing i wont have to be at w.o.t for the same speed and all. right?

 

[steelespike]

Re: first post guys!

Yes it could deliver better mileage. Mileage on a boat is a little different
than a car it is more fluid.Your motor uses a specific gph(gallons per hour)
at wot (wide open throttle)rule of thumb is gph= 10% or the rated hp.
120HP would be 12 gph at wot.Of course less at less throttle.The idea is to fine tune your setup so you get the most speed at a given throttle.Usually the most practical mileage is just above planing speed.But ideal mileage could be as much as 2,000 above planing speed rpm.flow meter is easiest way to tell but with extended use you may get a feel for it.