Need Prop Recommendation for 90HP Yamaha - More questions

[bc2009]

Iboats Boat and Motor Info
1. Year, make and model of boat
2004 Crestliner 1700 Super Hawk
2. Length, width and base weight of boat, look for boat decal on back of boat
17'7", 7'6", 1135lbs base
2a.What is the recommended HP for your boat
125 hp
3. Number of people and gallons of gas normally on boat
2 adults, 2 children, 12-17 gallons of gas
4. What do you use the boat for
Cruising, fishing
5. Is it a Deep Vee and if so how many degrees of deadrise
Deep Vee
6. Year, make and model of motor
2004 Yamaha 90TLRC
7. HP and gear ratio of motor IMPORTANT
90 HP, 2.0 Ratio
If you don?t know the ratio, you need to pull the plugs out and put a piece of tape across the prop and the lower unit and then cut it between the prop and the housing and turn the motor until the tape lines up with each other, it is easier if two people do this, so one can watch the prop while the other counts the revolutions of the motor
8. Manufacturer?s recommended Wide Open Throttle (WOT) range
4500-5500
9. Anti-ventilation Plate height above keel of boat if it is an outboard in inches
about even (maybe an inch higher than the keel - dark out...may need to re-do during the day)
10. Is it a bass boat or does it have a pad bottom
No
11. Does it have a hydrafoil, dolefin or trim tabs
No
12. Make, model, diameter, pitch and whether SS or aluminum prop
Aluminum Prop, Make: Michigan Match Aluminum (model 101033) 13.25" with 17 pitch
13. WOT RPM and speed from your current prop and how much gas and how many people were in the boat for the test data and is the speed by GPS. If you do not have a tach you can buy a Tiny Tach for $ 50
WOT: 4800, 12 gallons, 34 mph (not GPS), 2 adults/2children
14. Are you at sea level or a higher elevation, give us the elevation in feet
604 feet above Sea Level
15. Has your motor been tuned up lately and have you checked that the carburetor butterfly is opening all the way, checked compression, and looked at the plugs and checked spark, all of the foregoing could be the reason your prop is not attaining full RPM
16. How long has this prop been on the boat and why, at this time, do you think it is the wrong prop
Just bought the boat and it had this prop
17. Does the prop show any damage that you can see
No...
18. What problems are you trying to cure or what are you looking for the boat to do that it is not doing the way you think it should or to your expectations

I want to switch to a stainless steel prop and make sure the boat is running at its best, preferably stay with 3 blade...I would appreciate recommendations (fairly new to owning a boat). Looks like I do not have the right prop for the boat, but plan to save the aluminum for a spare.

 

[hwsiii]

Re: Need Prop Advice for 90HP Yamaha

Re: Need Prop Advice for 90HP Yamaha

B, I find that you have a 12% prop slip right now and that is not bad by buying a SS you ought to be able to redue that and gain some speed. I also show that you will need to hange to a 15" pith in order to get loser to your reommended WOT. That was an exellent form you filled out, everything we needed to find a better prop for your boat. I would reommend you ask Dhadley for a prop reommendation on the SS prop, just add his name to the end of your title and I am sure he will see it. If he hasn't seen it in a day or so I will make a reommendation for you, but he is better than I am.


H

 

[bc2009]

Re: Need Prop Recommendation for 90HP Yamaha - Dhadley

Re: Need Prop Recommendation for 90HP Yamaha - Dhadley

Thank you very much, hwsiii. Just to make sure, the 15" pitch is for stainless? Just out of curiosity, should pitch be similar on ss vs aluminum? Once I get a good prop on there, I will report my numbers again.

Dhadley - can you recommend a ss prop for my boat?
Thank you!
bc

 

[wellsc1]

Re: Need Prop Advice for 90HP Yamaha

Re: Need Prop Advice for 90HP Yamaha

You'll get good advice from this forum. Research for my prop, I discovered Yamaha uses a half-clever blade (or something like that). I put a full-bladed prop with a cupped design using same pitch and lost 1000 rpms, but gained about 8 - 10 mph. The motor could barely get on plane, revving no higher than 3000 rpm until it got on plane and slowly approached 4500 rpm. The engine was working way too hard.

I found a used (almost brand new) half-clever Yamaha prop in ss and am anxious to report my performance with a stock ss prop.

Listen to this forum. You'll be satisfied with the help.

 

[hwsiii]

Re: Need Prop Advice for 90HP Yamaha

Re: Need Prop Advice for 90HP Yamaha

B, the 15" is for aluminum props and most SS props but when you hange to SS there are many onsiderations to take into aount. In the Yamaha lineup of props alone I have seen differenes of 700 RPM between their performane series and the semi leaver. I use mathematis to find the starting point for a prop on someones boat, but in the end it is knowledge and experiene to find a better prop for someones boat. I will post a prop omparison hart for a friend of mine's boat using two performane series prop and the semi leaver. The semi leaver with a 17" pith and the performane series were a 18" and a 16" pith.

Prop omparison harts

arl an you tell me what your #WOT RPM and speed ended up being with your new prop.


H

 

[bc2009]

Re: Need Prop Recommendation for 90HP Yamaha - Dhadley

Re: Need Prop Recommendation for 90HP Yamaha - Dhadley

HWS and Carl - thank you for the info. Carl, I am interested in finding out how the Yamaha prop worked on your boat...and any other prop recommendations.

bc

 

[bc2009]

Re: Need Prop Recommendation for 90HP Yamaha - Dhadley

Re: Need Prop Recommendation for 90HP Yamaha - Dhadley

hwsiii,

Just some other questions - would I be better off going with a Yamaha OEM prop? After seeing the graphs you posted it almost seems like that might be the way to go if I went stainless. Also would I be missing out on anything if I just opted for aluminum? With so many choices for stainless, and the possiblity of blade geometry affecting my choice, I am not sure where to go.

Thank you!
bc

 

[bc2009]

Re: Need Prop Recommendation for 90HP Yamaha - More Questions

Re: Need Prop Recommendation for 90HP Yamaha - More Questions

Spoke with a local dealership today and they recommended trimming the motor up some to see if I can get the max RPM out of the aluminum prop (Yamaha recommends a 19" pitch on the motor, but I am assuming that is their 19" prop) - I think I have read in other posts that raising the motor will gain rpm...does it affect other things as well?

At this point I have changed my mind and will most likely get a new aluminum prop (Solas or Michigan Wheel?) - I am interested if anyone has any recommendations though.

Thank you!
bc

 

[hwsiii]

Re: Need Prop Recommendation for 90HP Yamaha - More questions

Do you mean that the 4,000 RPM at WOT was without the motor being trimmed up.

H

 

[bc2009]

Re: Need Prop Recommendation for 90HP Yamaha - More questions

4800 was trimmed down - yes to what you asked.

 

[hwsiii]

Re: Need Prop Recommendation for 90HP Yamaha - More questions

LOL, you ould gain another 400 or 500 RPM with it trimmed up,you need to give us new numbers trimmed up. My mistake, I assumed you knew you had to trim the motor up to get WOT RPM.



H

 

[bc2009]

Re: Need Prop Recommendation for 90HP Yamaha - More questions

I had no idea, but will give it a shot this weekend. Been away from boating for a while...slowly "working the rust out the gears" and remembering how things are done...

 

[hwsiii]

Re: Need Prop Recommendation for 90HP Yamaha - More questions

LOL OK


H

 

[bc2009]

Re: Need Prop Recommendation for 90HP Yamaha - More questions

Fresh off the river...changes to above, I was carrying 18 gallons of gas. Only got to 4900 RPM - I did trim higher, but think I experienced cavitation. Speed increased to 36MPH at WOT. Otherwise everything was the same.

 

[hwsiii]

Re: Need Prop Recommendation for 90HP Yamaha - More questions

B, I have seen those mihigan math props eat a lot of RPM without giving great speed before. Let me do some pondering tonight, and I will get with you tomorrow morning.


H

 

[bc2009]

Re: Need Prop Recommendation for 90HP Yamaha - More questions

Sounds good - I am open to suggestions on the prop (I really thought I would get a few more RPM out of it tonight).

I am not sure how this prop got on the boat as it is (bought the boat used with extremely low usage and thought it was OEM until I took it off and inspected it closer) - I will keep it as an emergency back-up...

Thank you, hwsiii!

bc

 

[hwsiii]

Re: Need Prop Recommendation for 90HP Yamaha - More questions

You are very welome.


H

 

[bc2009]

Re: Need Prop Recommendation for 90HP Yamaha - More questions

Just noticed I had made a mistake on the year of the boat...I corrected it to 2004...

 

[hwsiii]

Re: Need Prop Recommendation for 90HP Yamaha - More questions

B, here is the way to measure the anti ventilation plate height, please do this and let me know the height.

H

 

[bc2009]

Re: Need Prop Recommendation for 90HP Yamaha - More questions

The bottom of the keel is even with the antiventilation plate.

The boat does have a keel that is 1 inch deeper than the boat (by 1.5" wide). The measurement was from the bottom of the keel to the antiventilation plate.