Need help please

[Robin30588]

1996 hydrasport 23ft plus pulpit 6000lb
Evinrude Johnson viper prop 14 1/2 inch diameter, 19 pitch, 3 blades, standard rotation, stainless steel
WOT 5600-5800 rpms, max speed 30 mph
Johnson 1996 225hp
I'm trying to get the boat to plane faster and to get more top speed.
Is that top speed normal for that boat with that engine?

 

[Philster]

Re: Need help please

Just to be clear: You are getting 5800 RPMs from it at WOT and going 30 MPH?

How are you measuring speed?

Well, if you want a prop that will plane faster and get more speed, you can't really do both with one. If you get a better hole shot from a prop, you give up a little top end. If you focus on top end, you lose some hole shot.

The exception would be moving from an old, cheap alum to really good stainless steel (SS). The better design and stiffer material of the SS in the same pitch will give a wee bit better performance all around, but not much.

That's a pretty big load on a 225, so it's going to be pedestrian in terms of performance.

 

[Robin30588]

Re: Need help please

I'm measuring the speed using my gps. And yes 5600-5800 rpms and only getting 30 mph. Gas millage is terrible too

 

[steelespike]

Re: Need help please

5800 @ 30 mph I get 46% slip. Even at 6000lbs that seems like a lot of slip.
I think you could tie it to the dock and get less slip
I think something isn't right.
Using 20% slip with the same numbers you get about 3900 rpm.
Does the motor sound like it is screaming or is it just purring along casually.

 

[Robin30588]

Re: Need help please

Sounds like its screaming

 

[Philster]

Re: Need help please

Can we see a pic of how the engine is sitting on the boat? If it's too low or high, we'll be chasing our tails.

Side pic showing prop and AV plate in relation to bottom of boat.

 

[Robin30588]

Re: Need help please

 

[Maclin]

Re: Need help please

Perspective in photos can be deceiving, but it looks a little high to me.

Looks like the big clamp has some room to move down to the top of the transom cutout maybe...?

 

[Dhadley]

Re: Need help please

If it were mine I'd be tempted to have the tach checked for accuracy especially if it's a Faria. I had a 22 HS with a 200 OMC and ran a 17. It still only turned about 5400 and we had it on a 6" jackplate.

 

[QC]

Re: Need help please

For fun, I'd remove the transducer for a quick test. I agree it looks a little high, but only make one change at a time, and the transducer would be the easiest. It may be causing enough turbulence to introduce air which could cause ventilation (sucking surface air into propeller) which is the direction we are all pretty much thinking at this point. High mounting position could do the same.

Edit: I always suspect the tach as Dhadley has suggested. ALL numbers need to be accurate to draw any decent conclusions. The "screaming" comment lead me off that path, but the need for accuracy can not be overstated!

 

[Robin30588]

Re: Need help please



I also wanted to show you this thing that sticks out of the bottom 2 1/2 inches, I'm assuming its a thru the hull transducer.
could this be causing that problem?

 

[Robin30588]

Re: Need help please



Another view if it helps.

 

[steelespike]

Re: Need help please

The transducer could be causing problems and that little black device could be aggravating things even more. Is that patch near the transducer smooth? It could be adding to the equation.
5800 with a 1.86 ratio ,a 19" prop and 20% slip would produce about 45 mph.
However I do believe a 19" isn't going to make 5800 on a 6000 boat.

 

[QC]

Re: Need help please

Holy bump on the bottom Batman!! That combo of stuff could be really screwing things. I would not do anything until I had a smooth hull. I see three things: 1) Roughly a cylinder sticking down, 2) a rectangular thingee, and 3) the transducer (black thing on transom). Wow. First thing I'd do is find out what the cylinder and rectangle are for. Never seen that before, but cain't be good . . .

I see a need for a thread in the Restoration section with a shout out to oops! for some glassing lessons