4.3 Mercruiser prop choice

[90stingray]

Sorry all my speeds are not gps verified as to calculate prop slip... but please read on.

Overall goal is to prop the boat to 5000 rpm's with just me onboard, that way she will still have good grunt when loaded down. I really like the 4 blade aluminum props for pulling and low cost.

Well here goes... I have a 2001 Glastron GX185 that came with a 23p aluminum 3 blade and would turn 4800rpm and hit 50. I am looking for a better holeshot. I tried several props last year with no winners. I ended up living with a 21p 4 blade alum solas... she would turn 4600rpm and 45ish. So I bought a turning point 19p 4 blade alum and I am at 4600rpm and around 45 again.

I just can't see this boat with a 17p prop! But I just don't see any other options. I mean the 23p would get me to the right rpm, I shouldn't have to drop to a 17. Does the turning point have much more bite than the solas? Could it be mis-labled? Should I try a 17p turning point?

Let me know your thoughts...

 

[steelespike]

Re: 4.3 Mercruiser prop choice

Your trying to prop to an abnormally high number.My info indicates 4800 wot.
When going to a 4 blade they usually figure about a 200 rpm reduction just going to a 4 blade accompanied by a loss of speed.
You very likely changed brands and blade number so all bets are off.With the Turning Point you in affect changed brands twice.
So your 21" rpm change is tempered and the 200 rpm per inch is a rule of thumb not carved in stone.
It appears by the rule of thumb that a 19" 4 blade Solas prop will get you about 5000.
Perhaps less but of no consequence.The 19 will probably produce speeds about 43. @ wot.

 

[Slip Away]

Re: 4.3 Mercruiser prop choice

Solas, Turning Point that tells me right there.

Go with this. It will be what you need. Michigan Wheel 992204 Vortex 4-blade aluminum 14 x 20p.

 

[dcarver]

Re: 4.3 Mercruiser prop choice

The 4 blade 20p would probably be great. I just put a 4 blade 18p on my 4.3 and run about 40mph at 5000rpm and the hole shot is crazy good. I think the 20p would get you more speed at WOT and still have a good hole shot

 

[90stingray]

Re: 4.3 Mercruiser prop choice

Solas, Turning Point that tells me right there

Well tell me.... cause I am missing something.

Is it like going from alum to ss?... just to hard to predict? Does that turning point just have too much cupping? Original 23p is a black max if that helps. Solas look and feel, seemed middle of the road like the black max. Hustler is a different animal with each pair of blades looking different and is has the vent holes... guess I was expecting predictable results. I should have stayed solas and the rpm would have followed per the book.

It seems odd to go to a 20p from a 19p to get to a higher rpm...

 

[Slip Away]

Re: 4.3 Mercruiser prop choice

It's all in the quality of manufacturing, blade geometry and cupping. Trust me, the Vortex 20p 4-blade will be the cat's meow.

 

[90stingray]

Re: 4.3 Mercruiser prop choice

Cats meow? That sounds nice.

 

[90stingray]

Re: 4.3 Mercruiser prop choice

Well I got one on order from iboats !!! Upgraded shipping... Should be here by friday. We will see what happens.

 

[Slip Away]

Re: 4.3 Mercruiser prop choice

You also ordered a #102 or #202 XHS hub kit with the prop , correct ?

Please let us know how things work out.

 

[90stingray]

Re: 4.3 Mercruiser prop choice

Well i received the vortex today. The blades have less cupping than the hustler. I bet the rpm's will be up with this one. I hope the mph will still be there tho. Winds are 35+ now and are expected all weekend.... so I don't see a test ride happening. But I will report the results after I get her on the water.

 

[90stingray]

Re: 4.3 Mercruiser prop choice

Well it was still windy but we went out anyways. I made a few quick bursts and it seems like I am getting around 4800 rpms and 45 ish mph. Bow rise was kept to a minimum and hole shot was nice. Like I said it was rough so my numbers could be better once I find some smooth water. Overall I am satisfied so I am selling my other props via craigslist. Thanks.

 

[tahoejag]

Re: 4.3 Mercruiser prop choice

90 stingray - I recently installed the 14x20x4 Vortex. 47/48 mph (gps) wot - 4800 rpm with aprx 3600 lbs total weight. Very pleased with holeshot, lower planing speed, improved mid-range cruising. boat installed on is in signature.

 

[Slip Away]

Re: 4.3 Mercruiser prop choice

Good to hear the Vortex worked as planned. I thought you would like it.

 

[fish hook]

Re: 4.3 Mercruiser prop choice

Want to order a Vortex 4 blade today. Still deciding on 18p or 20p. My current Vortex 3 blade 19p works well i'm just afraid of losing the holeshot by going to the 20p 4 blade. Might just settle on the 18p as the top end is less attractive to me that hole shot and pulling for water sports. I have a 3 blade 21p I can always throw on for cruising. Anyone know of a reason to not go with the 18p? (my boat is an 04 Tahoe Q4 with the 4.3)

 

[Slip Away]

Re: 4.3 Mercruiser prop choice

Anyone know of a reason to not go with the 18p?

Depends on what your max RPM is with the 3 blade 19p.

 

[fish hook]

Re: 4.3 Mercruiser prop choice

Depends on what your max RPM is with the 3 blade 19p.

im around 4900 with the 19p 3 blade - thought i read to drop an inch of pitch when going to a 4 blade so i was thinking i might like the 18p performance

 

[steelespike]

First of all welcome. You should find lots of help with prop selection on this forum.
First thing to do is to open a new topic under the New Topic tab at the top of the prop forum page.
Here in this 2 year old topic your wasting your time especially if you expect replys of similar boats.
In the final results you will need a lightly loaded gps speed and accurate rpm.
Prop calculation is onlyn as accurate as the inputs Unfortunately the only surely accurate numbers we have
​ is the prop size and gear ratio.
It does appear that a 4 blade 19" prop should solve your problems. But you must be able to verify your results
for the best performance and long term health of your motor.
If we had the gps speed ,prop size and gear ratio we could tell if the tach makes sense.
Assuming 47 is accurate it appears your rpm is closer to 4300.
It is very common for both the tach and speed to be in question.Thus the need for gps speed.
Some cells can get a gps app
A moderator may move this for you,in the mean time get yourself a gps.