prop for 150 gt

[red10]

i have an 1983 ebbtide dynatrak 17'6" with a 1988 johnson gt150. The boat weighs about 1600 pounds loaded and i have a 21 pitch stiletto without a jackplate. The motor is in the middle hole which is about 1 inch above bottom of boat. my rpm's are 5600 and running 51 mph on gps. I'm wondering if my speed can be increased with a 23 pitch or a 4 blade prop because i think it should run faster than that, thanks

 

[red10]

Re: prop for 150 gt

i forgot to tell you it has a hydrofoil ( stingray) and it is a fish and ski boat

 

[JB]

Re: prop for 150 gt

Sounds like you are in the 10 ring already, Red.<br /><br />I suspect any change in prop will reduce your performance.

 

[ob]

Re: prop for 150 gt

What JB said.Only thing else you could do is play with the setup a bit by raising the engine to its optimal height.This will require a water test to insure excessive prop ventilation doesn't occur.Maybe a precise carb sychro adjustment could gain you a bit.Also consider that if the hydro foil you are presently running is riding too low when the engine is on plane it will rob you of a few Rs as well.

 

[LubeDude]

Re: prop for 150 gt

Sounds slow to me, I have no way of knowing what my boat weighs, but my 18' (glass) Bass Tracker is a f&S model, w/Mer 150 and I can turn a 14.25 X 27P Prop at 65 MPH GPS W/ two on board and gear. Granted they are different boats, but Im not sure they are 14 MPH different. Im running a 25P High Five now at 63-64 MPH. W/ great hole shot.

 

[red10]

Re: prop for 150 gt

ob, i raised the engine to the middle hole and now i don't have to trim as far, the hydrofoil is running on the surface. The motor has 25 hours on the rebuild and it was just synced and linked. I picked up 4 mph by switching from an aluminum 19" to a 21" stainless. Lubedude, this is where i was thinking something was not right because i was reading your post on the different props you have tested and that other boat you put smart tabs on. You guys know your s*** and i really appreciate your help and feedback. I started reading these posts 2 years ago and i have learned ALOT from all you wonderful people. Thanks again

 

[Dhadley]

Re: prop for 150 gt

Youre at about 15% slip now. Not bad but you might be a tad better. If you can use 100% of your trim range now, try raising the motor a hole or two.<br /><br />We can also suggest some very nice folks who make really nice jackplates......

 

[LubeDude]

Re: prop for 150 gt

Originally posted by red10:<br /> ob, i raised the engine to the middle hole and now i don't have to trim as far,

This has me believing that you are not able to trim out completly causing you to blow out, (lose bite), is this true?

 

[red10]

Re: prop for 150 gt

i can trim out about 1/3 on the trim gauge but i can't tell you what degree that is, it doesn't really blow out but the rpm's will raise a little more, i think i need to take the hydrofoil off and test without it. When i take a corner fairly hard it will blow out and start to hop if i don't trim back in almost all the way.

 

[LubeDude]

Re: prop for 150 gt

IMHO, I have always set up my own and others so that i can trim out all the way at WOT and have to just bump the trim down to hook up solid. I was that way with the 14.25 X 27 four blade i tested, IMHO that was perfect. Now with the High Five it is fine at full trim at WOT, So I am going to leave it. You will always have to trim down almost all the way when you make a turn, the more blades, the less you will have to trim down. Im thinking that maybe you are a bit too high on the transom now by what I am hearing.<br /><br />You say you are not blowing out, so why are you saying you do not have to trimm as much? What are you using as a guide? In other words, why are you stopping?

 

[texasfishon]

Re: prop for 150 gt

four blade will not speed you up.<br />i had a '87 stratos 179 w/150 johnson gt<br />no jackplate ran a 24 pitch RAKER and got about 60mph, but make sure it is a raker style prop.<br />can't remember my rpm and had to estimate mph because the probe would not stay down past 55mph.

 

[red10]

Re: prop for 150 gt

lube, i guess with the hydrofoil i thought that you really don't need to trim out all the way, maybe it is satrting to blow out but i need to try another run with the gps to verify my speed is decreasing if i trim out to far, maybe i can swing a 23 or 24 pitch if i do trim out further and not lose grip, i'm heading north for memorial weekend so i can run it again if there aren't to many boats out. Thanks again guys, any more input would be appreciated. I'll get back to you on the results, hopefully i can try a different prop that weekend to.

 

[KCLOST]

Re: prop for 150 gt

Red, Remember you have a crossflow engine not a Mercury looper... So the power isn't the same... However I would expect that you should be able to run a 23P prop on that baby, and still stay in the optimal rpm range...

 

[red10]

Re: prop for 150 gt

kclost, i think i might try a 23, i've heard these dynatraks with the same motor will go between 55-60 without a jackplate so i'm trying different things. I need 2 props anyways 1 for skiing and the other for fishing or light load. Thanks again

 

[red10]

Re: prop for 150 gt

guys i tried a 23 ballistic and it got me to 54 mph but had blowout issues in corners and trying to get on plane, it sure isn't a stiletto but it did get me more speed so i think i'll try a raker or something similar

 

[LubeDude]

Re: prop for 150 gt

What were your RPMs with the 23P. I think you need to try a 4 blade. Also, you always need to trim down when cornering or lower your jack plate if hydraulic.

 

[quantumleap]

Re: prop for 150 gt

I would lose the foil. You may be mounted a little high now but are getting better results because it is getting the foil out of the water. I would take a couple test runs with the motor mounted one hole lower with no foil and the 23P prop and see how she runs. You can always go to tabs to help with planing. Tabs would also help from blowing out it the corners as they help keep the boat level when cornering.

 

[red10]

Re: prop for 150 gt

lube, they were about 5500 rpm's and i took the hydrofoil off it didn't do much for speed but handling was 100% better and cornering, no jackplate, i'm much happier with this setup after taking the hydrofoil off.

 

[red10]

Re: prop for 150 gt

Quantum i must of been postin when you were, i think a 23 or 24 would be about right, i'm gonna try to get a 24 raker and see it does, so far the stiletto is the best i've run, just need more speed and keep the r's down when its just me in the boat, thanks again guys

 

[Mercathode]

Re: prop for 150 gt

Hi red <br />It has my experience to run OMC outboards a bit on the low side of the RPM range and get some good numbers as opposed to the MERCs which love to spin. I bet that 24 raker will sing a song and probably will clovk around 5200-5300 which I would say is ok! Get rid of the hydrofoil.<br />LW