Twin Yamaha 50's

Holoholo · Posted: Sun Jan 20, 2008 1:03 am Post subject: Twin Yamaha 50's

Hello,

I am somewhat new to this forum and have twin 2003 carb 50 4 stroke Yami's with 14" ss props on a CD22. I took my boat for a test run last week for the first time and saw that my max rpm was 4700 rpm, somewhat below the recommended 5000 - 6000 rpm. I have the normal load of fuel (50 gals), fishing gear and probably one other person. My top speed was about 28mph, which was fine, but I did notice it was sort of lugging to get up on plane.

Does anyone have this same type of power setup with the twin Yami's on a CD 22 where they can recommend a prop size that they are happy with?

It would save me the time of doing the trial by error.

Thanks.

Vern

hardee · Posted: Sun Jan 20, 2008 2:07 am Post subject: Twins

Hi Vern, Welcome,

My CD 22 came with twin 40 Yami's with the ProPulse, and a spare set. I think you will like the Twins, handling is great and I think you have the better power option. I will be interested to see how you do with the 50's. Will be watching here along with you.

Harvey
Sleepy C Moon

SEA3PO · Posted: Sun Jan 20, 2008 11:01 am Post subject:

Hi Vern... My boat has twin 40 Yamaha's...and once I did my own tune-up I think I am happy with them..... I can't reach top RPM either... Mine tops out at 4900... I probably will repitch with new props once I have ruined these sufficiently... I bet I have plowed several miles of sand...so I am more concerned with keeping er going forward at this point.... I can hardly imagine your 50's not topping out... are you sure the motors are broken in and tuned properly... mine were not... you also might check the throttle linkage at the engine to make sure your getting WOT at the motors...it may just be the linkage...

Joel
SEA3PO

Holoholo · Posted: Mon Jan 21, 2008 12:13 am Post subject: Twin 50 Yami Props

I purchased my '03 CD 22 in October and have finally gotten the motors tuned. They only had 100 hours on them but were not really babied as i generally do to my motors. Wow, having had EFI 4 strokes in the past, I did not the expect Yami carbs to be so sensitive. I was told that you should run the motors until the ethanol gas is burned completely so as not to prevent the varnish to build up. The motors came with 14" pitch SS props and after having lake trialed the boat, my mechanic said that if we resize with 11" props to start, he thinks that somewhere between that and maybe 13" ones, I should get into the 5500 - 6000 rpm range which is where the motors are speced. He said that i will not only get better hole shot but also maybe a little more top end speed that what we already were gettting at 29 mph. I know the CD22 gets squirley after about 30 mph so I was not expecting to get more speed, but just greater lower end pickup if I should ever need to get over a wave or avoid one. I did search on the "propeller" library but could not find anyone who had twin 50 Yamis, mostly Honda's (which I was told have different gearing).

I guess I am going to try resizing and keep these SS props for a backup. One other thing...I am going to aluminum props as I do notice a much louder gear engagement with the stainless props because of their weight (I believe) and hopefully by going to the alums, this will be a much smoother gear transition.

I will post my results once I complete the change over.

Vern

Holoholo · Posted: Mon Jan 21, 2008 12:17 am Post subject: Twin 40 Yamis

Seapo, what size pitch do you have on your 40's and are they alums or SS?

Vern

SEA3PO · Posted: Sat Aug 23, 2008 8:23 pm Post subject:

I just got home from Catalina...and the best I could turn was 4900 and that was between 20 to 20.4knots... wide open...
I looked at my stock props, and Yamaha is tricky not to tell you much...they are aluminum G series (whats that?) 13 pitch and I think they are 10 3/8"..... I really think those 40's should spin in the 5000 to 6000 range....so I am a bit low...I usually am a bit heavy but thats the way I am..... I think I should be able to go a bit smaller on the pitch and pick up the rpm...

Joel
SEA3PO

Wefings · Posted: Sat Aug 23, 2008 11:27 pm Post subject:

they can be massaged about an inch at a prop shop.....
Marc

Wefings · Posted: Sat Aug 23, 2008 11:56 pm Post subject:

in pitch that is...........
Marc

SEA3PO · Posted: Sun Aug 24, 2008 12:10 am Post subject:

So would you reduce the pitch from 13 to 12..... or just buy a new prop that is already at 12..... I can't imagine that a 10 3/8" prop is that much money...
I had the prop for the tug repaired and it was a bunch of money...course I did put a hell of a ding in it...Think that one is about 16" and bronze.

Joel
SEA3PO

Wefings · Posted: Sun Aug 24, 2008 12:35 am Post subject:

Yamaha brand props are fairly expensive . I suppose it depends on the charge to put em on the pitchblock . New ones are probably around a hundred bucks a piece or so . 12 " should be good with the Twins and if you buy new Yammie 12Ps you will go up to 10 5/8 in diameter . You will get a little more RPM pitching down with the 10 3/8 diameter you currently have . Then there is Solas , Mercury , Precision, Powertech ,Michigan Wheel, etc...........
Marc

Wefings · Posted: Sun Aug 24, 2008 12:41 am Post subject:

Also , if you haven't had the carbs synced [assuming you have em and I think you do ] do that first . They do get out of whack and it can make a pretty significant difference in top RPM.
Marc

SEA3PO · Posted: Sun Aug 24, 2008 12:49 am Post subject:

Wow...I am impressed... I just looked up Yamaha props on line...and the going price is roughly $92 each... there is one on EBAY new with 5 days to go...at $26...but new it will probably go high...

Your right about the next size is a 10 5/8" by 12.....

I tuned er up earlier and adjusted the carbs... but I think it would be worth it to have it checked....

Thanks

Joel
SEA3PO

Wefings · Posted: Sun Aug 24, 2008 1:02 am Post subject:

Gotta have a vacuum gauge set to do it accurately .
Marc

SEA3PO · Posted: Sun Aug 24, 2008 1:15 pm Post subject:

I used a Twinmax...that I use for my BMW motorcycle...it only does 2 cylinders...so I had to plug one...do 2 then change and do it that way....probably not the best... I have them pretty close...

What gave me problems was the idle mixture... they were way to lean...I opened them up and the motors ran much better....but what is the ideal ? I think I am open 3 turns... they originally were open 1 1/2 turns...but the motors lean misfired..

Joel
SEA3PO

SEA3PO · Posted: Sun Aug 24, 2008 2:21 pm Post subject:

I just saw an advertisement for prop re-pitching on line and for a prop under 11" they would change up or down 1" for $49... not bad...might give that a try... before I spend lots of money buying new props...

Joel
SEA3PO