2120 Y150 4s Reliance Prop vs. Porpoising

[greatcir]

Talking to Yamaha about a minor oil leak on my 150 somehow lead into a discussion of the Yamaha Reliance props.

Just wonder if anyone has tried one of the Reliance props?

I mentioned that at WOT I would porpoise & the only way to dampen it was to lower the motor or the trim tabs both actions slowed up the boat. I tried two different plates (cobra & a smooth plastic one) & both helped some but did not stop the problem. I tied a variable pitch prop and the factory Yamaha prop I got with the boat - 14 1/2 X 16 - seemed the correct prop. I tried 100 pounds of lead in the anchor locker and some help lowering the bow but not enogh to drag around another 100 pounds.

The Yammie engine man said the Reliance prop had been designed for the 150 4s and he thought it had some cup on the blades and povided enough lift to stop the porpoising.

Reason I ask is that seems to me the basic 2120 was designed for a 150 2s engine about 50 pounds lighter than the 150 4s yet both use the same hull. And the Reliance prop he suggested (14 1/2 X 15) has a Yamaha price of over $500.,,,,,,,,,,,,,,,,,Pete

 

[hakr]

Hmmm. The prop Parker shipped with my 2100CC is a black
"SS 15-1/4 x 15 -M" for an F150. I am curious how it is going to perform.
Seems like not much pitch.

 

[rplas48]

I have the 2120 with the F150 and have tried 3 different props. Results are from GPS and fuel flow meter.

133/4 X 17 black ss top RPM 5500 2.6 MPG at 38MPH, best cruise consumption at 4000-4300 at about 3.6 MPG at 24.3-27.5 MPH

14 1/4 X16 polished ss top RPM 5400 2.58MPG at 37 MPH best cruise consumption at 4000 RPM at 3.38 MPG at 26 MPH

151/4 X 15 ss top RPM 5400 2.6 MPG at 36 MPH best cruise consumption at 4000RPM at 3.7 mpg at 25.3 MPH

Not much difference however the 151/4 prop is about 4-5 pounds heavier and at 600-700RPM there is a definite " clunking" with this prop. I spoke with Eric at Parker and he confirmed that he has heard similar comments about this prop. The 151/4 prop did allow the 2120SC to stay up on plane at about 200RPM less that the others.

Yamaha we think ( one cateloge list it for only left hand while another list it for only right hand rotation) has come out with a reliance 14 1/2 X 15 prop that at first glance should be ideal for the 2120 SC and a F150. The lower pitch should allow the engine to get to the 5700-5800RPM while the larger diameter should allow quicker plane at lower RPM. Eric will try to get his hands on this prop and will retest the 2120SC.

Stay tuned.

Hopes this helps ....for the time being I am sticking with either the 141/4 or 133/4...do not like that gear clunking with the 151/4

Ray

 

[Outta Here]

I mentioned that at WOT I would porpoise & the only way to dampen it was to lower the motor or the trim tabs both actions slowed up the boat. Pete

Your boat runs faster while porpoiseing than when runnin level? Have you tried motor trim at vertical (about 4 bars) and enough tab to stop poropiseing? To get a good reading, run opposite directions.

 

[greatcir]

Yep, at WOT in the heat & warm water I'm at 35-36 MPH with trim up & engine up but in a few seconds the porpoising starts and gets dramatic quickly. So I can only kiss those speeds briefly. Have run with all sorts of trim & tab combos. Trimming the engine down to about half the bars with no tabs does okay or about the same as engine all the way up and tabs over half way down. Both take 2 MPH off the top. Usually have a full load of fuel to test but now about 3/4. Also wondering about fresh water vs. salt?

Speed is a bit more downstream which is obvious. Porpoising same up or down stream.

Not the way I want to run. Can hold 32 MPH no problem and sometimes 34 if there is light chop to dampen the bobbing. Slick calm boat still bounces at WOT so cannot hold the 35-36 under any conditions.

Just hate to put out money for the Reliance prop if it is not an answer to the bobbing. May wait till I have time to install the 12X18 Lencos but seems to me if they are trimmed down at all it still adds drag. ,,,,,,,,,,,Pete

 

[greatcir]

I finally found a good local prop shop. We talked about the new Yamaha Reliance prop that Yamaha suggested for my 2120 F150 ( to stop porpoising as it may have some cup in it compared to my current prop. The Reliance Yamaha suggests is a 14 1/2 X 15.

My prop shop man said he can cup my current Yamaha ss 14 1/4 X 16 for $30 and that he can also reverse the cupping. Because I would lose some RPM's he also said he can modify the pitch some but not all the way to the blade throat because he would be into inflexible casting material there.

I have no problem getting him to cup my 14 1/4 X 16 and understand it may lower WOT RPM, but what does anyone here think about him trying to reduce the pitch as close as he can to 15 ? ,,,,,,,,,,,,,,,,,,,Pete

 

[plattapuss]

A permatrim and 12x18's completly eliminated all porpoising on my 2120 w/f200

 

[greatcir]

Thanks for replies above. I have tried two hydrofoil type plates and they both provided me more butt lift, but both were squirrley in turns and were not the total answer so I removed them. Left the holes so easy to go back. I also tried 100 pounds of lead in the anchor locker and it got the bow down some but seemed to aggravate the porpoising.

I took off my factory 3 blade ss 14 1/4 X 16 and had it heavily cupped for $35. They could not safely change the pitch so just cupped it which means I'll lose WOT RPMs. This prop is now providing the best performance I have had in all my experiments which suggests to me the Reliance 14 1/2 X 15 might be the best prop for my 150 4s in spite of its price.

I still have the factory 12X12 Lencos on but have the 12X18's in my garage waiting till later this year to hang when I trailer for a bit.

I ran alone the factory 3 blade ss 14 1/4 X 16 heavily cupped prop with all sorts of motor and trim tab settings & here are my figures from running two directions in very light fresh water chop on 80 degree water with factory 12 X12 tabs and 3/4 load of fuel using GPS speeds and no hydrofoil plate on my 2007 2120:

4,000 RPM, 7 bars up motor trim, no trim tabs, 27 MPH, 3.55 MPG
4,500 RPM, 7 bars up mtr + 3 bars dwn trim, 31.4 MPH, 3.34 MPG
5,000 RPM, 9 bars up mtr + 5 bars down trim, 35 MPH, 3.00 MPG
5.000 RPM, 9 bars and no trim, porpoising bad, 36 MPH
5,000 RPM, 6 bars up mtr. and no trim tabs 34.2 MPH
5,300 RPM, 6 bars and no trim, WOT 37 MPH 2.4 MPG
5,300 RPM, 7 bars no trim WOT 37.3 MPH, 2.4 MPG
5,400 RPM, 8 bars mtr no trim WOT 38.1 MPH 2.4 MPG
5,400 RPM, 10 bars up mtr, no trim WOT 38.4 MPH, 2.4 MPG
5.500 RPM, 11 bars (max) no trim WOT 38.1 MPH 2.38 MPG
last number began to slowly porpoise, trim tabs stopped it but lost speed

So looks like cupping the prop took off over 200 RPM at WOT as expected. Surprise to me was the boat came out of the hole with the motor trimmed down and no trim tabs without any problem. I have a lighted Lenco trim gauge so I can see the exact number of down bars it takes to kill the porpoising for the port and starboard trim tabs.

I'm a fast runner so don't care about lower than 30 MPH in most of my running. Since I am able now to get higher speed without porpoising, I am finally headed in the right direction.

I may add the Cobra plate back on the engine since it bolts under the cavitation plate and rerun the the tests above before I buy the new Reliance prop or install the 12 X18 trim tabs. I will not reinstall the plastic Sting Ray hydrofoil stabilizer since it makes me nervous about bolting it on top of the engine plate after seeing postings here.

Just seems to me the boat should be able to run WOT with no trim tabs in slack water without porpoising and that trim tabs have to add drag. My engine is factory set in the middle holes.

Bout all I know today....................Pete

 

[Outta Here]

So what was the oil leak?

 

[greatcir]

FishFactory - Since I'm not losing any measurable oil so I just clean it off when I come in on the lift. Have about 70 hours now so will probably put it back on the trailer at 100 hour and do bunch of odds & ends - Yamaha visit on oil drip, add new 12 X18 tabs, etc.

Just ran my 2007 2120 150 4s with the heavily cupped 3b ss 14 1/4 X 16 and the ss Cobra hydrofoil plate. Full of fuel two directions. Basically, the porpoising is worse with the Cobra plate on so will remove it next convenient time. Lost about 200 RPM WOT with the cupping and another 200 RPM WOT with the plate.

4000 RPM, 6 bars up mtr, 2 bars dwn. trim tabs,26.1 MPH 3.22 MPG
4500 RPM, 8 bars up mtr, 6 bars dwn trim, 29,3 MPH 3.05 MPG
5000 RPM, 9 bars up mtr, 7 bars dwn trim, 34 MPH 2.68 MPG
5300 RPM, 9 bars up, no trim, WOT Porpoising 37 MPH 2.37 MPG
took 6 bars of down trim tab to reduce the bouncing dropping to 36 MPH

Had slight porpoising at 4500 RPM and at 5000 RPM could not do with less than 7 bars of down trim tab to kill porpoising.

I count 10 bars as the all up trim with the motor and 8 bars max. down with the port & stb. trim tabs.

Not sure what my next best option is so may talk to Parker & Yamaha again. ,,,,,,,,,,,,,,,,,,,,Pete

 

[Outta Here]

Looks like you're runnin' from 6 bars to 9 bars up on the motor trim?

If so, no wonder you're porpoising. Neutral on motor trim is around 4 bars showing, quite often I have only 3 showing. By kickin' the motor out, you're raising the bow, causing more porpoising. Raising the motor and lowering the tabs, if that's what you're doing is counter-productive...killing speed and fuel milege.

 

[greatcir]

FishFactory - I did talk to Jeff at Parker and he said the 2120's have a tendency to porpoise at WOT in clam water, but of course that is not their design point.

He was not excited about me installing the 12 X 18 tabs I have in hand to calm the matter but he was interested in how my cupped prop had done. He said in the next 60 days they would problay test the new Reliance prop even though it was very limited in sizes. Yamaha had told him the Reliance was aimed at the 150 4s for issues like mine. Yamaha also said to keep trimming up as long as the speed was increasing.

I had run all the bars on the trim tabs and my engine but only showed the optimum values for the numbers I posted above. For clarification here are the bar numbers for with the Coba on and off. I took it off today to make the run without it.

2007 2120, 150 4s, full fuel and two passengers, 3 blade ss 14 1/4 X 16 heavily cupped, Cobra ss plate, all at WOT

4 bars motor, no trim, 4,900 RPM, 31.5 MPH
5 bars motor, no trim, 5,100 RPM, 33.6 MPH
7 bars motor, no trim, 5,200 RPM, 34.9 MPH 2.22 MPG, minor porpoising
8 bars motor, 5 trim, 5,300 RPM, 34.6 MPH 2.20 MPG, needed trim

Took Cobra plate off - all else same

1 bar, 0 trim, 5,000 RPM, 34.6 MPH, 2.35 MPG
2 bars, 0 trim, 5,100 RPM, 35 MPH. 2.33 MPG
3 bars, 0 trim, 5,100 RPM, 35.2 MPH, 2.33 MPG
4 bars, 0 trim, 5,100 RPM, 35.4 MPH, 2.33 MPG
5 bars, 0 trim, 5,100 RPM, 35.7 MPH, 2.32 MPG
6 bars, 0 trim, 5,200 RPM, 35 MPH, 2.30 MPG
7 bars, 3 trim, 5,100 RPM, 34.8 MPH, 2.30 MPG needed trim
8 bars, 4 trim, 5,100 RPM, 35 MPH, 2.33 MPG needed trim to dampen
9 bars, 4 trim, 5,200 RPM, 35.8 MPH, 2.34 MPG, needed trim
10 bars, 10 trim, 5,300 RPM, 35 MPH, 2.26 MPG, needed all trim

Tests went quick with the admiaral recording stuff after the boat settled down at each peg and we were on a short cruise too in calm water. Results are remarkably similar on this test for 1 through 10 engine bars.

I plan to leave off the Cobra plate. The cupped prop does make boat handling much better in my opinion. I had to give up some RPMs with my curent prop to get the handling. So all still leads me to believe the Reliance 14 1/2 X 15 is where I need to go. ,,,,,,,,,,,,,,,,,,,,,,,,,,Pete

 

[hakr]

5300 RPM is too low for an engine that WOT's at 6000 rpm.

 

[greatcir]

hakar - yer corrent and I should have mentioned that. I would like to be between 5,500 and 6,000. If I go to the Reliance Yamaha is suggesting it should put me in that range.,,,,,,,,,,,,,,,,,,,,,,Pete