Is My Boat Slow or Normal?

[Restless22]

I'm running a 1988 Wellcraft Aruba 232 with a 350 Magnum and Alpha 1 outdrive. I'm now running a 17p SS prop, which to me, feels like it's much faster and easier to plane than the dinged up 15p that was on it with old exhaust manifolds.

GPS shows approx 31-33 MPH at 4000 rpm, and when pushed harder, speed doesn't really increase.

My boat is 5100 lbs dry according to the specs, and it's very comfortable and smooth riding at the current speeds and RPMs.

Is my boat slow, or is this normal?

 

[NHGuy]

Re: Is My Boat Slow or Normal?

If you leave er wide open what do the rpms get to? The motor should turn 4600 to 4800 at wide open.
Once you get it onto plane you should raise the drive enough to improve your speed, this reduces the wetted surface. Experiment with it.
Start off easy, roll into the throttle, don't just hammer it from a stop. Start out with the drive all the way down, once on plane trim it up to what feels best. In chop you'll want to keep the nose lower to cut the waves. In flat you can raise it more. If you trim too high the boat may porpoise, lower the drive a couple of clicks. And if you raise it so far that the prop starts to lose bite bring it down till it grabs. You don't want to overrev the motor.
If you can only get 4200 or 4400 rpm you may want a 15 pitch prop. You want a prop that turns the recommended wide open throttle rpm.
Your boat ain't slow, it's just kinda big!

 

[Restless22]

Re: Is My Boat Slow or Normal?

Yeah, it's 24" and looks thick compared to the Sea Rays parked beside her. The hull is not quite as sleek as the Rays.

 

[Restless22]

Re: Is My Boat Slow or Normal?

I can go for the higher RPMs, but the speed doesn't increase. I guess I'm skittish with the RPMs, and I like cruising at the low 30s and the kids have fun on the tubes. I'm just not sure the boat has more speed in her.

 

[NHGuy]

Re: Is My Boat Slow or Normal?

I'm not encouraging you to run it full blast. Just recommending you get all that the motor & hull have available. That's done by getting the right prop & trimming things as you go.
My boat is an old semi go-fast. So I run it up to the limit once in a while. But I don't stay there long cause it feels like there are big dollar signs $ going out the exhaust when it's really tooling along.

 

[Restless22]

Re: Is My Boat Slow or Normal?

I feel ya' bro. The play time costs $$$, and I'm watching the gauge, lol.

 

[Maclin]

Re: Is My Boat Slow or Normal?

What top RPM can the engine reach now when it is run at WOT long enough to see if it is doing all it can do?

 

[Restless22]

Re: Is My Boat Slow or Normal?

I can run it almost up to 5000, but I never run there long. My boat seems happy in the 3700-3900 range in the low 30 MPH range. I guess I'm happy there too.

 

[Restless22]

Re: Is My Boat Slow or Normal?

My Google Fu on the specs of the boat indicates that 32.2 is the top speed, and 25.3 or so is the cruising speed. So, I guess I'm normal?

 

[Maclin]

Re: Is My Boat Slow or Normal?

Sounds like you are spot on to me, I recommend enjoying it as is. Don't change a thing or even start thinking about it or you will be wasting energy and resources chasing the Mo-Better phantom prop, only to end up right back where you are now!

 

[QC]

Re: Is My Boat Slow or Normal?

I think she has more speed in her, but not sure how you plan to get it if you won't run the RPM up. That's how you do it. Also, I don't think you have answered anything about trim. Are you trimming up? Have you tried sitting at your 4000 RPM point and trimming up and down? Your numbers kind of add up, so I believe the tach, the speed, etc. I am using 1.5 gear ratio. The 350 Mag in '88 was rated 270 at the crank which would translate to around 240 at the prop as they are rated today, so she's not a powerhouse despite the Mag label. I think this is a 40 MPH boat, but you gotta let her run. Also, if she planes easily now, and she reaches 5000 RPM, I am thinking a 19" pitch is probably "right".

However . . . I totally agree with Maclin too, if you don't actually wanna go faster, then stick with what you got and go boating.

 

[Restless22]

Re: Is My Boat Slow or Normal?

I think she has more speed in her, but not sure how you plan to get it if you won't run the RPM up. That's how you do it. Also, I don't think you have answered anything about trim. Are you trimming up? Have you tried sitting at your 4000 RPM point and trimming up and down? Your numbers kind of add up, so I believe the tach, the speed, etc. I am using 1.5 gear ratio. The 350 Mag in '88 was rated 270 at the crank which would translate to around 240 at the prop as they are rated today, so she's not a powerhouse despite the Mag label. I think this is a 40 MPH boat, but you gotta let her run. Also, if she planes easily now, and she reaches 5000 RPM, I am thinking a 19" pitch is probably "right".

However . . . I totally agree with Maclin too, if you don't actually wanna go faster, then stick with what you got and go boating.

Yes, I'm trimming up. I trim up to the point of cavitation and keep the throttle up to avoid porpoising. I have the "feel" for where I need everything to be to stay smooth. I'm still learning though. I bought a nice used 19P Quicksilver SS prop, but the 17P SS on there now seems "right". I wonder what a 19P would feel like?

 

[QC]

Re: Is My Boat Slow or Normal?

If you are getting 5000 RPM out of the 17, then the 19 should be faster at all RPM points, and should top out around 4800. A little slower to plane. What's the bottom look like? I don't understand, if you are trimming out, why you don't get any speed increase above 4000 RPM. That's not normal if the prop, the bottom and all is kosher. I have heard of prop hubs that "spin" at high loads. I don't usually believe it, but I guess it's possible.

Oh, and BTW, what people often call cavitation is actually ventilation. Sounds like you are trimming right though.

 

[Restless22]

Re: Is My Boat Slow or Normal?

The bottom is nice. It's always lived on a Boat Port, and I rinse it with fresh water each time it comes out of the lake.