Is my boat going fast enough?

[xPauliex]

Hi, I'm a new member and this is my first post. I just recently bought a 2000 Starcraft 17' bowrider with a 3.0L 135hp Mercruiser. With just myself in the boat At WOT I am topping out at 34-35mph on GPS. From what I've read I think I should be closer to 40mph. Can anyone tell me if this is the right top speed for this boat? Below are the specs:

Boat dry weight - 2330lbs
My weight - 200lbs
Gear - 100lbs
WOT RPM - 4400
Prop - 14" x 19p

If there's any other info needed please let me know. Any help is appreciated.

Thanks,
Paul

 

[yhsesq]

wot rpm should be 5500 i think. drop to a 13 pitch prop.

 

[Scott Danforth]

the RPM range on the 3.0 is 4600 RPM NOT 5500.

you could drop back to a 17 pitch which will help the hole shot, however on a boat that large and heavy with a 3.0, 35mph is about right. you will want to verify your tach with a shop tach, and your speed should be verified by GPS

my Avanti had a 3.0, and I could hit 41mph on the GPS, however the boat was 1650# and the OMC had a slightly different gear ratio than your mercruiser. that 600# makes a difference.

 

[SkiDad]

I think your speed is typical and fast enough for water sports. The hull design has a lot to do with it. are you trimming up a little ?

 

[xPauliex]

Thanks for the help guys. I knew the boat was heavy so thought that might be why I wasn't reaching 40mph like I've read for other bow riders of the same length.

I changed the prop to a 14.5" x 17p last week but was not happy with the result. The hole shot was a tiny bit faster, top speed remained the same and RPM increased by 200 but I lost the soft steering. It pulled hard to the left at WOT.

With the 19p I have trimmed up to the ideal spot where the boat rides nicely on plane and doesn't pull to any direction. And yes 35mph is plenty for the kids to tube and ski. Most of the time they don't want to go that fast. Lol

Do you know if I can put a 21p on the Mercruiser? Would this increase top speed? I know it'll take longer to get on plane. I'm just curious about this. Ideally I want the engine to run at optimal performance and not necessarily top speed.

Thanks again for your help.

 

[eavega]

Do you know if I can put a 21p on the Mercruiser? Would this increase top speed? I know it'll take longer to get on plane. I'm just curious about this. Ideally I want the engine to run at optimal performance and not necessarily top speed.

Thanks again for your help.

You COULD put a 21P prop on there, but at the expense of about another 400 RPM, which would drop you into "lugging" territory, and probably have trouble getting up on plane. You are good with a 19P in terms of RPM (and speed, My boat also has a 3.0L Mercruiser and will just top 40 MPH lightly loaded with a 19P sst 3-blade prop @ 4500 RPM, but my hull weighs 1850 Lbs. Like Scott Danforth says, that extra weight makes a difference). At this point you can play around in the 17P-19P range with different materials (Aluminum vs Stainless) and different manufacturers (cupping and venting would make some difference), but that could be an expensive road to travel for an additional 3-4 MPH.

Rgds

-E

 

[SkiDad]

the new prop probably has more cupping to it . there is a trim tab above the prop - if you loosen it and turn to the left it and re-tighten it will combat the torque steer - but if you are happy with the 19 then maybe just keep it for a spare - always good to have a spare.

if you are new to boating these are some speeds that are fairly safe

Tubes with kids - 15-20 mph - most people pull way too fast !
Young skiers 15-20 mph
adult skiers on 2 skis 22-26 mph (it depends on weight and/or skill)
youth slalom skiers - 22-24 mph
adult slalom skiers - 26-30 mph (it depends on weight and/or skill)

the faster you go the water gets a lot harder when you fall.

 

[xPauliex]

Thanks for all the input guys. You've confirmed what I've wanted to know which is, is the boat running at optimal performance? And it sounds like it is. I'm gonna keep the 17p for a spare and I will play with the trim tab (thanks for letting me know about that Skidad). I've been boating for about 20 years but never really took the time to get to know the engine and specifics of my boat (my father usually handled it) so I'm trying to learn as much as possible with the new boat to keep it looking good and running for years. Cheers!

Paul

 

[littlerayray]

In setup with a 21 p 14.25 diameter prop and my boat is 18.5 I got the 3.0 mercruiser for a motor what is the gear ratio on the out drive mine is 2.00 I am also purchasing a 4 bladed prop btw with 1/2 tank and me on board I can get up to 45 mph on GPS wot fully loaded I get about 35 mph

 

[xPauliex]

That's a good question. I think I have the alpha one gen2 which would be 2.00 gear ratio for that year. Can anyone confirm?