Best prop for 2000 Fourwinns Sundowner 205

[stant1man]

I recently repowered my boat with a new 5.7 vortec with 4bbl quadrajet and 315-320hp... it previously had a 5.0GL so I have some prop questions...

A little brief history... previous owner hydro'd the 5.0... had a recon 5.7 fitted but never ran... this 5.7 spun a big end on our first trip out before even getting on the plane hence why i skipped straight to a brand new motor...

Outdrive is a Penta SX-M 1.79 and the current prop is a Quicksilver High Five 23pitch...

Boat behaviour - Slow to get onto plane even though it is revving to 4k..... once it gets on the plane the engine will rev to 4800 wot and gets a top speed of 42-43mph(dash)... I expected at least 50mph.

The current prop has little plastic plugs with small holes to vent exhaust gasses and I wonder if perhaps these are causing too much cavitation when trying to plane away.

I am looking for advice on why the boat is so slow to plane... could this be the vents as I know the high five is a holeshot propeller...

I would like everyone like to find the best balance of accelleration / economy and top speed... I am thinking about a quality 3 blade but would be keen to know your thoughts on this.

To recap -

2000 Sundowner 205 21ft Cuddy
5.7 vortec 4bbl 315-320hp
Outdrive SX-M 1.79
Current Prop Quicksilver Highfive 23p

Any advice on a prop swap would be really appreciated,

Best wishes,


Stan

 

[steelespike]

Re: Best prop for 2000 Fourwinns Sundowner 205

prop calculator indicates 52 mph at 10% slip.
I think your first stop should be a gps to pin down the speed.
If your specs are accurate your slip is way over 20%The holes could be too much.
Wouldn't hurt to plug them.Hole shot is supposed to be the h5s forte.And as I understand it the H5 likes lots of power.

 

[stant1man]

Re: Best prop for 2000 Fourwinns Sundowner 205

prop calculator indicates 52 mph at 10% slip.
I think your first stop should be a gps to pin down the speed.
If your specs are accurate your slip is way over 20%The holes could be too much.
Wouldn't hurt to plug them.Hole shot is supposed to be the h5s forte.And as I understand it the H5 likes lots of power.

Ok, it looks like the holes need to go, i suspect they are for smaller engines that don't have the power to spin it up at low revs and my boat is certainly not lacking in that department. I even suspected I could go a pitch higher as my WOT is in the high range. I'll let you know the results.

Is there anything else that can contribute to the slip?

 

[steelespike]

Re: Best prop for 2000 Fourwinns Sundowner 205

We're assuming its slip it could be your speedo.
According to my limited info the 5.7 is rated at 5,000.The motor will br happier reving freely within its rpm rating.
Are you sure about the 1.79 ratio? Again my limited info indicates a 4.3 is 1.66,the 5.0 is 1.51 and a 5.7 is 1.43.Your 1.79 seems closer to a 3.0 number (1.97) than a 5.7 at 1.43.

 

[stant1man]

Re: Best prop for 2000 Fourwinns Sundowner 205

Yes SX-M 1.79 is stamped on the side of the outdrive and it was shipped with a 5.0GL 2bbl... my last boat was a fletcher gto 170 with a inline 6 115 mercury.... it topped out at 47mph and this boat feels way slower in every respect. I will check tomorrow with GPS and will also have the holes plugged.

Thanks again for all your assistance, it's much appreciated.

 

[stant1man]

Re: Best prop for 2000 Fourwinns Sundowner 205

We're assuming its slip it could be your speedo.
According to my limited info the 5.7 is rated at 5,000.The motor will br happier reving freely within its rpm rating.
Are you sure about the 1.79 ratio? Again my limited info indicates a 4.3 is 1.66,the 5.0 is 1.51 and a 5.7 is 1.43.Your 1.79 seems closer to a 3.0 number (1.97) than a 5.7 at 1.43.

Ok had the boat out yesterday afternoon and at WOT 4700-4800 RPM the GPS confirms the speedo is spot on at 45mph trimmed out to optimal.... i blanked the prop vents but didn't notice any difference.

This can't be right... a 26ft cruiser was cruising along side me and turns out he has the same motor except runs duo prop... I couldn't get away! When I discussed it with him at the dock he said that his friend lost a load of top end running a high 5 and the only thing it was good for was creating a good wake for boarding... could a prop really cause me to lose 10mph over what she should actually do?

I just don't know what prop to buy, this is my first sterndrive and all my previous experience was with outboards where having tried just about every prop out there I found the michigan wheel ballistic to be the absolute ultimate with no comparison. Can anyone make a recommendation?

 

[DBreskin]

Re: Best prop for 2000 Fourwinns Sundowner 205

With everything else being equal, a three-blade prop should have a higher top end than a five blade prop. The three blade has two fewer blades to push through the water; less resistance than the five blade.

The three blade may have more slip, so you may want to increase pitch as compared to the five blade 23p.

 

[QC]

Re: Best prop for 2000 Fourwinns Sundowner 205

Need to verify the tach too . . . I don't think I'd do anything until I was sure the data was right. I also don't understand the 4000 RPM while trying to get her to plane. Something still very odd here.

 

[stant1man]

Re: Best prop for 2000 Fourwinns Sundowner 205

Need to verify the tach too . . . I don't think I'd do anything until I was sure the data was right. I also don't understand the 4000 RPM while trying to get her to plane. Something still very odd here.

I verified the tach using an inductive pickup, it's definately working ok... Basically if the boat is sat in forward gear and I give it full throttle the engine will rev to 4000rpm immediately and the boat will start to lift, then once on the plane and there is less load the rpms increase along with the speed.

 

[QC]

Re: Best prop for 2000 Fourwinns Sundowner 205

Where is the anti-ventilation plate in relation to the bottom of the keel? This sounds like ventilation to me or some other issue. High Fives should indeed have good hole shot although I am not sure about 23" pitch for this combo.

 

[stant1man]

Re: Best prop for 2000 Fourwinns Sundowner 205

Where is the anti-ventilation plate in relation to the bottom of the keel? This sounds like ventilation to me or some other issue. High Fives should indeed have good hole shot although I am not sure about 23" pitch for this combo.

It's the original Penta sx-m sterndrive that came with the boat from new. I am going to swap the prop for something else... Not sure what though. Seasons starting soon so any thoughts would be welcomed.

Best wishes,

Stan

 

[steelespike]

Re: Best prop for 2000 Fourwinns Sundowner 205

I'm sure no high five expert but it seems to me I read somewhere that they work best on high powered fast boats.
If so it would seem a 21 cruiserish type isn't the best choice for a high 5.
You might consider a 23" 4 blade should help your high slip (22%)And improve the hole shot.
If it gets to 4800 and 10% slip about 52 seems possible.It does seem that 300+ horses would be good for more. once finally setup.

 

[stant1man]

Re: Best prop for 2000 Fourwinns Sundowner 205

I'm sure no high five expert but it seems to me I read somewhere that they work best on high powered fast boats.
If so it would seem a 21 cruiserish type isn't the best choice for a high 5.
You might consider a 23" 4 blade should help your high slip (22%)And improve the hole shot.
If it gets to 4800 and 10% slip about 52 seems possible.It does seem that 300+ horses would be good for more. once finally setup.

Thanks for the advice, I am considering a 4 blade Michigan Wheel Ballistic as I enjoyed my 3 blade on my Fletcher but again, any other thoughts are welcomed on the best choice for our summer of fun

 

[QC]

Re: Best prop for 2000 Fourwinns Sundowner 205

My experience with High 5s is that they are great for hole shot, and not so great for top speed. Fastest boats typically run 3 Blades, and most all arounder 50MPH guys (me included) run four blades. I cannot comment on the Ballistic, but a decent 4 blade stainless should help a lot! However that is "should" and if the slip goes down RPM will probably drop as well, and I see a potential for a 22 inch. Most four blades are sold in even number pitch. I agree that this engine is probably setup for 5000 RPM, but without data from the engine builder, I can't really say. Still seems a little messy to be buying props, but I don't think you have much choice unless there is some way to try a few from friends etc.

My comment about the AV plate height is despite it being determined by the hole in the transom, it could be wrong If it was too high, that could explain the high rev and the high slip. Dunno. It should be even to less than an inch above the bottom of the keel when trimmed "flat' in relation to the hull.

 

[Philster]

Re: Best prop for 2000 Fourwinns Sundowner 205

The jump from 3-blader to 4-blader is a litte top end lost while gaining some low-end and mid-range punch.

The jump from 4-blader to 5-blader does not work like that. The dynamics change greatly. You need more horsepower than might actually match the hull in some ways, and the 5-blader provides response and snap not normally available, but it requires power to spare or a certain kind of gearing that takes some load off the engine.

Run-abouts, cruisers and common sport boats tend to* have power, engines, drives, designs, gearing and the types of use that fit within the parameters of the many flavors of 3-blade and 4-balde props (sizes, pitch, rake, cupping, etc).

*This means one can chime in here with an exception to the rule and bounce some isolated, anedoctal case and it doesn't run contrary to my post.

 

[sasada]

Re: Best prop for 2000 Fourwinns Sundowner 205

Hey stant1man I sent you a PM.

 

[Tail_Gunner]

Re: Best prop for 2000 Fourwinns Sundowner 205

Something is amiss here. timing is the most likey culprit. What size of four barrel carb...what type of ignition system...And this a new 5.7 vortec engine??? Is the hull clean....300 hp engine is a 20' boat with a 1.79 drive should lurch out of the water. Take a grease pen and mark the outer hub of the prop and create a line to the center Nut...Do a run and see if you can that get the line to move.

 

[stant1man]

Re: Best prop for 2000 Fourwinns Sundowner 205

Something is amiss here. timing is the most likey culprit. What size of four barrel carb...what type of ignition system...And this a new 5.7 vortec engine??? Is the hull clean....300 hp engine is a 20' boat with a 1.79 drive should lurch out of the water. Take a grease pen and mark the outer hub of the prop and create a line to the center boat on nut...Do a run and see if you can that get the line to move.

It's a new engine, new distributer, carb etc ... this is it here - http://www.michiganmotorz.com/vortec-marine-engine-silver-package-19672012-replacement-p-58.html

My hull has antifouling paint that is flaking off... i don't need to renew it as it is kept trailered and is only used in fresh water. Could the slightly rough paint be my problem??? Its not "that" bad...

I can do the hub test like you suggest this coming weekend

 

[QC]

Re: Best prop for 2000 Fourwinns Sundowner 205

It's a new engine

Could be messed up no matter how new . . .

My hull has antifouling paint that is flaking off... i don't need to renew it as it is kept trailered and is only used in fresh water. Could the slightly rough paint be my problem??? Its not "that" bad...

Could be. Could cause the ventilation I am worried about (4K RPM during hole shot). And will affect top speed as well.

 

[Tail_Gunner]

Re: Best prop for 2000 Fourwinns Sundowner 205

It's a new engine, new distributer, carb etc ... this is it here - http://www.michiganmotorz.com/vortec-marine-engine-silver-package-19672012-replacement-p-58.html

My hull has antifouling paint that is flaking off... i don't need to renew it as it is kept trailered and is only used in fresh water. Could the slightly rough paint be my problem??? Its not "that" bad...

I can do the hub test like you suggest this coming weekend

If you have not checked the timing do so. Easy enough to do..Go to the I/O section and ask around....there is spefic way im sure you need to use a shunt....

http://www.marinemechanic.com/site/page229.html


Ohh yes as QC stated flaky paint could cause ventalation