RPM's for Properly Powered 2120SC with F200 4-stroke

[itguy]

I haven't been able to find what RPM's to expect on a 2120SC with 200 HP 4-stroke. Does anyone know what I should expect, or is there a way to find this on Parker's web site?

Thanks.

Itguy

 

[DaleH]

Find MAX RPMs of the motor you have (search on-line, see your Owner's Manual, or call your dealer or Yamaha) ... you should ideally be no more than 300 RPMs off that number.

 

[itguy]

Dale,

Thanks. An article in 08 Boating Life shows the 200 4-stroke produces 200 HP at 5500 RPMs. I think the last time I looked at WOT on my 2120 I was at 5200 and doing about 35 or 36 knots.

It looks as if I'm just barely within acceptible range.

Itguy

 

[Micheal J]

Dale,

Thanks. An article in 08 Boating Life shows the 200 4-stroke produces 200 HP at 5500 RPMs. I think the last time I looked at WOT on my 2120 I was at 5200 and doing about 35 or 36 knots.

It looks as if I'm just barely within acceptible range.

Itguy

Sounds about right. I have the same motor on my 08 2120sc and turn the same rpms as you do now,but not quite that speed.I am normally loaded up w/dive gear,or water in the bait tank though.
I did raise my motor 1 bolt hole up,and that brought the rpm's up a touch,and helped w/ the mpg's also.
I'm running the stock Yamaha prop it came with.375 hours ,and goin strong.
MJ.

 

[jethro]

For best performance and engine life the motor needs to be propped so that you are at or near 6000 RPM when at WOT with a full load and the motor trimmed to the most efficient spot.

This is what the owner's manual and Yamaha themselves have to say.

 

[JWL]

For best performance and engine life the motor needs to be propped so that you are at or near 6000 RPM when at WOT with a full load and the motor trimmed to the most efficient spot.

This is what the owner's manual and Yamaha themselves have to say.

It has been my experience that most outboards are over propped from the dealer.

 

[rloomis]

Dale,

Thanks. An article in 08 Boating Life shows the 200 4-stroke produces 200 HP at 5500 RPMs. I think the last time I looked at WOT on my 2120 I was at 5200 and doing about 35 or 36 knots.

It looks as if I'm just barely within acceptible range.

Itguy

I also hit 35 at 5500rpm on my 2120 running with the F225, but with the extra power, I still got some throttle left and can brush up against 6000rpm at WOT. Let me guess, you're running a 15x17 prop?
If so, you might want to drop to a 15pitch. You'll probably get an extra couple hundred rpm putting you about where you want to be at WOT.

Here's some plots of speed/rpm/mpg I got on my rig:
http://www.classicparker.com/phpBB2/vie ... php?t=5616

I have a 15 3/4 x 15 saltwater series II on order and should be arriving any day now. I'll take another set of numbers as soon as I get the new prop mounted.

 

[M5]

I have a 15 1/2 x 15 saltwater series II on order and should be arriving any day now. I'll take another set of numbers as soon as I get the new prop mounted.

I have a 2004 2121 with the F200 and the stock black SS 15 x 17 T prop.

Did you ever run any tests on that 15 1/2 x 15 saltwater series II prop.

Wondering if anyone else has a 2120 and has switched from the stock 15 x 17 prop.

Thanks,
Kevin (M5)

 

[rloomis]

I have a 15 3/4 x 15 saltwater series II on order and should be arriving any day now. I'll take another set of numbers as soon as I get the new prop mounted.

I have a 2004 2121 with the F200 and the stock black SS 15 x 17 T prop.

Did you ever run any tests on that 15 3/4 x 15 saltwater series II prop.

Wondering if anyone else has a 2120 and has switched from the stock 15 x 17 prop.

Thanks,
Kevin (M5)

The chart data for the SWSII prop is spotty since my first and only chance so far to run with the new prop was on a short wine&cheese cruise with my wife. Anyway, here's what I got so far:

I went WOT but the engine went 6100 to almost 6200 RPM's so I backed off immediately. Overall, I lost about 3mph at the top end, hitting about 38mph@5800 instead of 41mph@5800 with the 17BS.

The 17BS would take about 5sec to get on plane and needed over 3800RPM and a speed close to 23-24MPH to stay on plane.
The 15SWS would get on plane pretty much instantly. About as quickly as the engine rev'd up to 3800 or so, I was on plane and I could hold it going a much slower speed of around 17-18MPH.

The fuel economy with 15SWS was mostly around 2.4MPG through a pretty wide range of RPM's between 4000-5000 with a peak 2.56MPG at 4000RPM.
The 17BS hit a peak 2.52MPG at a very narrow 4300-4400RPM range which would put my speed around 28-29MPH, too fast to be a comfortable ride in most common conditions.

Overall, the prop change did most of what I wanted. The boat is much more responsive and I could run much slower through choppy offshore seas, still staying on plane at 3800-4000RPM getting over 8% better MPG (2.56MPG vs 2.35MPG) than running those same RPM's with the 17BS where I was fighting to keep the speed down but still stay on plane.

Another difference between the two props is the 15SWS would grip the water at a much higher engine trim than the 17BS could. If I went too far and ventilated, I'd have to drop the engine way down to re-grab the water column and then I could trim really far back up again. So the 15SWSII was definitely providing a lot more grip and lift.
Lastly, calculating prop slip at 5800RPM, the 15SWS came in around 5-7% as opposed to 11-13% on the 17BS and at 4000RPM the 15SWS was about 18% instead of 25% with the 17BS.


Prop Nirvana might be found if there were such a thing as a 15.5x16SWSII, or maybe if I tried the next pitch up, 15.5x17SWSII, and raise the engine up a notch?

Anybody got a 17pitch SWSII I could take for a spin?

 

[M5]

rloomis

Now that's some great information.

Looks like that Saltwater Series II prop is working out well.

I have another question.

I was looking at the Yamaha website and could not find the 15 1/2 x 15 saltwater series II prop.

They have a 15 3/4 x 15 and a 15 1/2 x 17.

Any thoughts?

Thanks,
Kevin (M5)

 

[rloomis]

you're right, it's 15 3/4 x 15! My prop is the 6D0-45796-00-00 from the list you posted. I edited my posts above to fix that. I'll fix the text in the chart after I get more data and generate a new one.