Not happy with current prop

[mischmat]

Looking into changing the prop on my boat. Currently have an unknown 13 1/4 x 17 aluminium which I'm not overly happy with. The two I'm looking at is the Stiletto Advantage 1 13 1/4 x 15 and a Nemesis Quicksilver 13 1/4 x 17. Right now I'm on the lowest holes for the motor which has the motor at it's highest point and getting about 4700-4800 RPM WOT. The boat is a 1984 17'6" double eagle (deep V) and motor is an 84 Yamaha. Opinions?

 

[StingRay_90V4]

We need to know how many horse power the motor is ? As well as its too speed. Preferably GPS to on speed. As most Speedo's are a tiny bit off. Mine is off by one milenoer hour. Also, what about your current prop do you not like ? Its top speed ? Or its hole shot you don't like ? Based on your wot rpm you may need a lower pitch prop to attain a slightly higher rpm at wot. I had to okay aroung with my setup also until I could hit 5500rpm at 40+mph on my 16' bowrider with a 90hp rude.

 

[SkiDad]

those are both good props - are you trying to go faster, or more take off power or better ride ?

 

[mischmat]

Sorry thought I put the HP in there. It's a 90HP Yammie. Motor tops out 35mph @ 4800rpm cruising at 41-4200rpm @ 26mph

Things I don't like:

1. Mid range plane. I have a hard time keeping it on plane in the mid 3000rpm range.
2. Hole shot. I hit the throttle seems like it cavitates until the wake pushes back off the transom, then it planes out and picks up speed. (too much flex?)
3. At high trim boat doesn't handle well hard to describe but just feels off.
4. It's aluminum :laugh:

 

[SkiDad]

your numbers seem ok slip wise, i would try lowering the engine 1 hole - sounds like you are sucking air on take off. That might help your handling too if steering is sloppy. I do think your engine is showing it's age and might benefit from a 15 pitch prop - the stiletto won't be it though b/c that won't change your RPM and might actually lower - the stilettos are pretty aggressive - You need to get your RPM up some. you might try the Nemesis 15p or a good Solas 3 blade AL in 15p - you might loose 1-2 mph. Another to look into is a 15 or 16 pitch Powertech Red3 prop. The guy that will really be able to help you is Steelspike - i'm sure he be saying something soon.

 

[StingRay_90V4]

Steelspike knows his stiff. He made some recommendations that helped the performance of my 16' bow rider. I went from 32mph and a crazy whole shot to 41ish mph at wot @5500rpm with a still great whole shot with a 90 HP evinrude v4. I had to raise my motor one hole and switch props. Now I have great hole shot and gained almost ten mph . That's a lot.. I would try a 15p prop to and see what it does. And maybe lower your engine one hole. And you may even pick a few mph if you have the right prop and get the motor up too its recommended rpm range.

 

[mischmat]

Reason I'm up as high as I am is based of a lot of reading and watching youtube videos on proper height. This motor was originally mounted as low as it could go. Raising to where I'm at appears to have helped fuel economy. I took a closer look at the prop and it appears to have been hit at one point in time also, I can just see difference in bends near the tips so somebody may have bent the tips back effectively changing pitch? I guess my notes aren't going to matter as I can't verify prop integrity, however this prop looks to be more economy (cheap) than a quality prop.

 

[mischmat]

Leaning towards the Nemesis, 15 pitch, if this motor is getting tired. Should get RPM up appropriately gain some lift in the rear hopefully not lose the top end (since I don't have much to begin with.) Guess next question what hub kit?

 

[steelespike]

Don't get a prop yet.
Is the Double Eagle a brand or a model?Is it a true Deep V?I think they have a deadrise around 16 or 18 degrees at the transom.
Is the boat glass or aluminum?
New Yamaha tests of the 90 2 st. w 17" prop about 17' 1800 lbs tested weight they make 5500 to 5600 wot at about 42 mph.
18' 2400 lbs 17" about 39 @ 5400.
From your description I wonder if the boat has absorbed water over the years. The foam under the floor absorbs water from poor storage.
On the trailer without proper cover, snow ice and water soaking the interior possibly for years.
Also sometimes sitting at the dock for weeks or months with water in them.Often results with slow hole shot and struggling to stay on plane
26 surely seems enough speed to maintain plane.
Is the motor in excellent tune? does it have good compression?
Is the timing set right and advancing as it should?
Is the throttle opening all the way?
Is the bottom clean and smooth?
If the prop needs work get it repaired and get us a lightly loaded test with rpm and the gps speed.

 

[mischmat]

Double Eagle is brand. Model I'm unsure. It's a deep V.

Boat is Glass

Water could be in the foam I can't check without drilling. The transom is dry when I installed the sounder wood came out dry.

Previous owner kept it open, and under a cover. Snow... what's that again? Seats were redone so they are light and dry.

Previous owner trailered, as do I.

26mph it's planed but hard to keep it when doing about 20 mph I have to keep playing with throttle

Carbs were rebuilt by previous owner, tune seems fine to me.

Timing I'm not sure.

Throttle I'm not sure

Looking at the bottom it appears there's about 8 layers of peeling foul paint it's fairly thick in spots.

It'll cost me more to get it repaired than buy new. Nobody within 100 miles does it.

Yikes I hadn't thought about half these question

 

[steelespike]

I think you should verify the tach. Borrow a shop tach or buy a induction tach.
Check the selector switch on the back of your tach.Note the position and operate it a few times to
clean the contacts.
Your present slip is at 9% That is unlikely at 4800 rpm with that rough bottom paint.
Double digit slip is usually more typical. 10 - 13% on a well setup boat.
Is your speed by gps?
When you find low slip the tach becomes suspect especially with the low indicated rpm.
Does the boat respond to up trim?Gets up on the water with about 1/3 to 1/2 in the water?
Does it lay down flat at speed like its glued to the water,not much responce to up trim?
If it is trailered how come 8 layers of anti foul paint?
If we tried to make up 700 rpm with a prop you would be at a 13 or 14" pitch
about what you would find on a pontoon.
If the prop is from 84 it could actually be worn enough to actually measure.
If you boat where there is sand and silt wear may be obvious.
Most of todays props are more advanced than the 1980s
The solas Amita or Rubex are good al props with a good reputation.
With your complaints and assuming the motor is doing the best it can a 16" solas 4 blade prop
should help your complaints.Any reduction in pitch may slow top end a little the 4 blade usually costs a little speed.
​ A 1" reduction should keep your rpm around the same.If we assume it is actually higher than indicated
that may be reasonable.A ss prop is an unnecessary expense Unless we investigate the unknown problems.
I have to rest my typing finger.

 

[mischmat]

Hoy, I have some stuff to do. Guess I need to figure out if my readings are in fact correct.