Yamaha F150 prop

[gt]

Alumacraft Trophy 195 (hull wt ~1900)
2010 Yamaha F150
Motor mounted 1 hole up
Yamaha Reliance SS prop, 19"p
WOT ~41mph (gps) @5200rpm (low end of 5k-6k range)

2 guys in the boat, hole shot is fine, although boat seems to list slightly to port under power.

Put a couple more guys in the back seats, hole shot is a struggle, and can get a very slight porposing at speed after hitting a wave (not uncontrollable, and goes away after a while)

I've read where a 4 blade prop will give me just a tad more stern lift (fact or fiction). Would this help the porposing?

Was thinking about a 17" 3 blade, or 16" 4 blade. Not really concerned with top end, as much as feeling like I gotta get out and push with a full boat. Although I don't want to lose TOO much top end..

Props are $$$! I'd like to get this right the 1st time.

Thanks in advance for the help.
Gary

[Philster]

1) 4-blade, 17P SS prop with vent holes.

2) Smart Tabs (self-actuating trim tabs) round out the package perfectly.

Solves all your problems.

That's it. If you'd like, skip the tabs and run the new prop. If she porpoises, lower the engine and see what happens. Personally, there is nothing like doing it right top to bottom, so I recommend 1 + 2.

[BaileysBoat]

Too much prop. You need to get to 5800 or more at WOT or she is going to lug and make oil.

The problem you are up against is your rig is rated for a 200 and you are at the lower end, 75% of the rated power.

http://www.yamahaoutboards.com/sites...95-f200txr.pdf
Running the above test with 4 or 5 passengers would need a drop to a 19P.

If you go into the Yamaha website the 185 Trophy with the F150 uses a 19P Reliance and pulls 5700 rpm WOT light load.
In the real world with a full load that unit needs a 17 or 18.

http://www.yamahaoutboards.com/sites...sa669d.tmp.pdf

You have a bigger boat. I would try the stock 17P Yamaha aluminum, and raise the engine up one hole.
That's what I run on the Stanley, 44mph/5800 rpm.

I tried a 17P Turning Point Hustler on the Stanley but it was no better than the Yamaha aluminum, although the exhaust vents could help your hole shot.

Going to a 4 blade will lose you too much RPM.

Good Luck

[Philster]

^^^No

BaileysBoat:

He has some porpoisong, so we are not going higher on engine height. So scratch that idea.

Four-blade props knock off RPM if you don't change pitch. So, your claim is misleading to say the least.

Going to a vented 4-blade prop @ 17p is a slam dunk next step. RPMs will actually increase a little, the extra blade and vents help with all other issues and if you toss in tabs, it's a money setup all day and night.
.

You're entitled to your opinion, but a couple of your comments about blades/pitch and engine height are in direct contrast to everything known about solving the issues at hand.

[gt]

So if I remember my #s correctly,
staying with same # blades, I gain about 200rpms for each inch of pitch I reduce.
and to go from 3 blade, to 4 blade, to retain same rpms, I need to reduce 1" pitch
so going from 19" 3 blade to 17" 4 blade, I should gain about 200 rpms?
Did I do my math right?

Do you have any opinions on what I mentioned about gaining stern lift with the 4 blade? I've thought about the smart tabs, and am trying to get away without them, as I'll need to do something creative with my transducers.

[BaileysBoat]

Hey Phil, not my intention to mislead. I was typing my post and did not see your response. I agree that He needs to drop to a 17P, but a 3 blade of the same pitch should give a little more RPM, and GT will probably need it. The Yamaha 17P aluminum works very well on the F150, and would make an inexpensive test prop. The other thing to consider is the GT is new to the boat and the porpoising might be a learning thing? I was not aware that raising the engine would cause porpoising?

[Philster]

So if I remember my #s correctly,
staying with same # blades, I gain about 200rpms for each inch of pitch I reduce.
and to go from 3 blade, to 4 blade, to retain same rpms, I need to reduce 1" pitch
so going from 19" 3 blade to 17" 4 blade, I should gain about 200 rpms?
Did I do my math right?

Do you have any opinions on what I mentioned about gaining stern lift with the 4 blade? I've thought about the smart tabs, and am trying to get away without them, as I'll need to do something creative with my transducers.

Spot on. Most newer 4-blades offer better stern lift, counter some porpoising, etc. Your numbers are correct, too. Might not need tabs: correct. Always nice to have though, but considering your issues, solve problems with prop and/or engine height for now.

[gt]

Thanks for the feedback guys. So do you think since I want to try the 4 blade, I should drop to 16", or stick with 17". And there are several manufacturers out there, any preference?

[Philster]

I stepped you down two sizes to 1st step down is to counter the effect of the extra blade and the 2nd is to raise RPM a little.

I only know about Merc props. The Trophy would be the prop to have. If you want to see about its competitors, just google 'better prop than Trophy'. Merc props can be pricey. There are likley some competitors that are 99% as good at 80% of the cost.

Edit: Decent options are Solas Rubex or Stilleto Bay Pro III

[BaileysBoat]

Hey GT,

I was wondering how you made out?

[gt]

Ended up going with a Michigan Apollo 16" 4 blade. Did what I wanted, and the price was reasonable (on sale here). Gave me about 300 rpm increase at WOT, and only lost about 1 mph. Hole shot with 2 onboard is obviously better, will see next month on vacation, how it is with a full boat. Porposing is gone. Only issue, I feel an intermittent vibration at speed. Not sure if this is the prop or not, as I am also hearing an intermittent noise at idle speed in gear (kind of like a bucket of bolts, maybe a timing issue?) . Gonna put the old prop back on when I have a chance and see if this goes away. Can a new prop cause a vibration at speed? If I accelerate, the vibe goes away as I accelerate, but then comes back as soon as the RPMs level out.
Thanks for all the advice..

[Avon 620]

Hi i have an Avon 620 with a 2009 yamaha f 150 mounted with the stock black stainless steel prop it came with, With a 75 liters fuel tank and 3 people the wot is only 5200 revs at 45 mph gps , the motor is trimmed in the middle of the gauge but when I higher it more the rib handling comes very bad it starts moving left to right and is uncontrollable. Any suggestions what can i do please. I thought of raising the motor but i'm afraid it will get air because its not mounted too deep

[smitty477]

Hello Avon,

"Hi i have an Avon 620 with a 2009 yamaha f 150 mounted with the stock black stainless steel prop it came with"

In order for the folks here to be able to help you it will be necessary for you to fully describe your current prop.
Your black painted SS prop will have a diameter and pitch number as well as a letter.
These will be cast in the outer 'drum'as well as where the hub meets the washer which takes the torque.
It will say something like 13-3/4 X 17 M.

Hope this helps

[Avon 620]

[QUOTE=smitty477;3884544]Hello Avon,

"Hi i have an Avon 620 with a 2009 yamaha f 150 mounted with the stock black stainless steel prop it came with"

HI sorry for the delay, today i took out my prop and the numbers are : 13 3/4 x 21-M does this mean its 21 pitch?
As i said before at wot it only revs 5200 with normal load of 6 people.
I also took a photo of the outboard so you can help me if it's mounted in the right position,the photo you can watch it here
https://www.dropbox.com/sh/00zbb5fey...f:DSC00189.JPG

Thanks for your help for now

[smitty477]

Avon 620 -
That is a 21" pitched painted SS prop common on a Yamaha of that size. I would suggest you get your rpm's up to at least the 5,500- 5,600 area and higher than that is normally preferred. You have a 2:1 ratio in your lower gear so you can use that as well for prop calculations.
The picture you show seems to indicate that the antiventilation plate is maybe a couple inches below the lowest keel point which is low. Often these props will run well with that anti vent plate at or just higher then the keel - gaining some rpm's..
Your options to go to a 19" pitch 3 blade will likely yield about 5,600 rpms as a guess - different brands will vary as well.
Similarly going to a 17" pitch 3 blade might leave you at 6,000 at WOT as another guess.

If top speed is not an important goal and you might have extra weight on the boat a smaller pitch prop is a better choice.
I do not know what you mean by "handling comes very bad it starts moving left to right and is uncontrollable." but often a 4 blade prop can help control porpoising to a degree. A 4 blade prop of 'equal' rpm will have a picth of about 1" less so a 17" 3 blade is about equal to a 16" 4 blade all else being equal.
I am not a prop expert but do have the Ymaha 150F's in my use - hopefully one of the other more knowledgable prop folks will chime in here as well.
Hope this helps