5200 RPM or 5700 RPM - Which is better??

[FrankWhoa]

I have a trusted buddy of mine who has raced bikes, four wheelers, and fished as long as I can remember. He tells me that his experience tells him that if I'm running my boat at 5200 rpm with a 27p, Vmax @ 71mph and better handling and plane that I am putting extra strain on my motor compared to running it at 5700 with a 25p Tempest @ 69 mph, still good handling and plane?

Does this make sense to any of you "mechanically inclined" individuals? He has nothing to gain by misleading me. Just an old man passing on knowledge.

[21XDC]

Lugging the motor at lower rpms is harmfull to a 2 stroke. 5700 is a better rpm range for the motor in my opinion. Have you tried a 25T1 V-Max prop?

[hooken203]

If you are running a SHO you should be running it closer to 6000. As Mike said better to let it spin up higher than to lug it. You might also find its faster.

[woppercatcher]

I'm not an expert by any means but looking at the SHO 225 specs the max hp is at 5500 and the full throttle range is 5000-6000. So it looks like you may not be getting the max hp out of your motor if your at 5200 wot rpm. Your not bogging it down and I would think as long as your convertable with that speed and performance your motor will last longer. And 21XDC, the SHO is a 4 stroke not a two stroke and a 4.2 liter tractor of an engine at that I don't think you could bog it down if you tried.

[TD]Prop Shaft Horsepower[/TD]
[TD]225hp at 5500 rpm (VF225LA) Full Throttle RPM Range 5000 - 6000[/TD]

[BassinBarrister]

Lugging the motor at lower rpms is harmfull to a 2 stroke. 5700 is a better rpm range for the motor in my opinion. Have you tried a 25T1 V-Max prop?

[FrankWhoa]

No I haven't tried the 25T1 yet but another buddy of mine has a 200 SHO with a 25 and is around 5500 on a slightly smaller Skeeter. It is a 4 stroke though as woppercatcher stated. The guy who told me this is a 2 stroke guy.

What about simply cruising around 4000 rpm, would that be considered lugging it too?

[ChrisCarsonMarine]

Go back aways and read "detonation and preignition defined" in general,Chris

[woppercatcher]

Reading the OP's original message he is operating in the recommended full throttle RPM range which is 5000-6000 according to Yamaha for that moter.

With full gear, 1/2 tank, me (200 lbs), light chop, 65 degrees, and:
1) a VMax 27 vented @ 1.5" prop to pad - 71 mph @ 5200 rpm GPS
2) a Tempest Plus 25" @ 3.5" prop to pad - 69 mph @ 5700 rpm GPS

Now, I do think the best prop is the 25p as that is also the manufacture's standard prop as well but to say that running at 5200 will cause motor damage is just a guess. If that was true then if you never got your boat to WOT let's say you ran at 4000 rpm most of the time your motor would break. I run my motor between 3000-3500 after on plane most of the time and I will bet my motor will last longer than if I ran it at 6000 rpm all the time. The OP is running in the recommended full throttle range set by Yamaha and if it breaks then they should have an issue with Yamaha. Should they use a different prop, well that is just an opinion as well.

[Rich Z]

woppercatcher,
Let me put to you this way. Get on your bicycle and ride up a hill in the low gear. I’d bet you wont have any problems. Now ride up that same hill again in a high gear and see how far you get. It doest matter if it’s a two or a four stroke. No matter what motor with over pitched prop it will eventually begin to detonate and fail much sooner.

[FrankWhoa]

Am I actually over pitched then would be the next question since I am within the max RPM range?

Not trying to be testy, I just want to understand the theory, application, and difference in it all so here goes.

According to Chris' detonation pin (very informative), being under a heavy load at low rpm is a problem.
Is running on plane considered a heavy load?
Is that theoretically possible on a prop thats only 2" pitch over the manufactures recommendation and in water?
In that case, wouldn't more prop slip occur negating the "heavy load" unlike a car tire on concrete with a heavy load?

Speaking of cars, why is it ok to run our cars at a lower rpm?
Are the new SHO 4 stroke computer controlled $20,000 outboards full of the same features that allow that in a car?

I definitely want my motor to last as long as possible and if burning through 30 gallons a trip at 6000 rpm with my wife and son is the solution, I need to explain that to her. She may decide to stay home. J/J

Thanks

[astroinfo]

Looks to me like you are in the correct rpm ranges for that motor, only important thing I would think is just don't stay at a constant rpm for a long period of time. I personally prefer the 25t1 but I dont fish huge lakes, mostly rivers with alot of bends where I have to get on and off the throttle constantly, cut throughs etc. But if I fished larger lakes I think i would install your 27p that seems to be the better deal.

[21XDC]

No matter 2 or 4 stroke, Every rig/combo should be propped to reach max rpms for that motor at wide open throttle....

[hooken203]

In the service manual it says Max. Output @ 6000 r/min 200 225 250. So the way I read that is if you want to get the max output you paid for you need to turn it at or near 6000. Yes if you are over proped at WOT then you are over proped at all RPMs. You may also find that your fuel economy goes up if you turn it a little higher due to the fact that you will be putting less load on the engine at all RPM ranges. Also your numbers dont add up. Run them in a prop slip calculator if you turn a 27 p at 5200 and then a 25p at 5700 you should go faster by a very small amount. Not slow down 3 mph. If it were me i would have the 25 looked at by a good prop guy and thats what I would run and let the engine turn 5700 to 5900.

[woppercatcher]

woppercatcher,
Let me put to you this way. Get on your bicycle and ride up a hill in the low gear. I’d bet you wont have any problems. Now ride up that same hill again in a high gear and see how far you get. It doest matter if it’s a two or a four stroke. No matter what motor with over pitched prop it will eventually begin to detonate and fail much sooner.

That may be true but he is not overpitched according to the specs. The specs say: Prop Shaft Horsepower 225hp at 5500 rpm (VF225LA) Full Throttle RPM Range 5000 - 6000. He is turning 5200 which is in the specs. Yes, he is not getting the full hp out of the motor and I do agree he could use a different prop but he is within the specs of the manufacture. So to say he is hurting the motor is just a guess and I would believe Yamaha who builds the motor over opinions on the internet.

[Rich Z]

So to say he is hurting the motor is just a guess and I would believe Yamaha who builds the motor over opinions on the internet.

Ok, you go ahead and believe Yamaha and everything they say.We already know what happened to many earlier model SHOs.

I agree with hooken that the numbers he provided just don’t add up.

[FrankWhoa]

Using what prop calc? I've ran the numbers on two myself and all they told me was how much slip I was having. I had the 25 worked on recently and the numbers stayed pretty much the same give or take a few.

The tempest is a smaller diameter prop 14 1/2" (or 14 3/4" maybe) where as the Vmax is 15 1/8". These two props should have different slip considering prop to pad, stern lift, etc. or is there something else I am missing?

[huntc]

hmmm?

[Rich Z]

Frank, That boat/motor will run best with 26p TXP at 2 3/4 below pad 72-74 easily 5700-5800rpm.

[hooken203]

The service manual says Max out put at 6000 rpm for all of the SHO engines. I tend to believe the service manual over other printed info. Yamaha is notrious for several different versions of thier specs. Is he damaging the engine by running it at 5200 proably not could the boat run better with the engine turning at higher RPM Yes.

[guss101]

are the sho's supposed to run a non-vented prop? from what i was told is that vented props are for the two strokes and ventless for the sho's? also was told that the ventless props give the motor a few hundred more rpms. he said hes running a vented 27 at 5200. if the vent/ventless theory is right a ventless 27 would get him closer to 5500