Yamaha VMAX max rpm=4000??

[dkjensen]

Hi
Just bought my frist boat. A campion 565s from 2004 with a Yamaha VMax 150 carb from 98. The motor is origin a trp, but last owner changed to a normal single prop..

I wonder why the motor only reaches 4000 rpm. It runs very well. It reaches The max rpm very fast, so i have no reason to belive That its over prop'ed.

Any idea?

Im a newbee to boats, so be kindly

Best regards

J?rgen (Denmark)

 

[99yam40]

see if you can find a rig like yours on here to see what prop they used and what they got out of it
http://yamahaoutboards.com/owner-resources/performance-bulletins

 

[dkjensen]

Thanks 99.. But No matches.
I can see in the manual that it should have a max at 5500 rpm.

 

[99yam40]

find something close to it in size ,weight, and shape maybe.
Yamaha shops should have test wheels for test running a motor to see if it can run as it should creating the designed Power/RPM.
if it passes that then you are left with rigging or prop problems

 

[ClassicAQ]

What are the prop specifics for the prop installed on your engine? Diameter and pitch (D x P), stainless steel (SS) or aluminum (AL). Some props will only have the diameter and pitch stamped on the hub. But if your prop offers more information, such as manufacturer and model/series, reply back with this information.

Along with the yamaha bulletins mentioned, you can also try using the yamaha prop selector: http://www.yamahapropselector.com/propSelector/web/inner.html

The type of boat you'll want to choose is a "runabout", then enter in other information it asks. It will spit out a few prop recommendations. Its the pitch of these props you'll want to pay attention to.

 

[dkjensen]

What are the prop specifics for the prop installed on your engine? Diameter and pitch (D x P), stainless steel (SS) or aluminum (AL). Some props will only have the diameter and pitch stamped on the hub. But if your prop offers more information, such as manufacturer and model/series, reply back with this information.

Along with the yamaha bulletins mentioned, you can also try using the yamaha prop selector: http://www.yamahapropselector.com/propSelector/web/inner.html

The type of boat you'll want to choose is a "runabout", then enter in other information it asks. It will spit out a few prop recommendations. Its the pitch of these props you'll want to pay attention to.

But the enigine reaches max rpm in 3-4 seconds.. so is There any reason to think about prop?

 

[ClassicAQ]

But the enigine reaches max rpm in 3-4 seconds.. so is There any reason to think about prop?

Your engine is NOT reaching spec max rpm at WOT. And the amount of time the engine takes to reach max rpms is an entirely other subject. The spec rpm range for your engine is 4500-5500. Preferably you'll want the engine to reach the top end of this spec range, 5500. You said your engine max rpm is 4000. So what you're experiencing is either an over propped engine, a poorly performing engine, or both. If you'd like assistance figuring out the issue, reply back with answers to my questions in my previous post.

 

[ClassicAQ]

I wonder why the motor only reaches 4000 rpm. It runs very well. It reaches The max rpm very fast, so i have no reason to belive That its over prop'ed.

But the enigine reaches max rpm in 3-4 seconds.. so is There any reason to think about prop?

Both of your posts noted above are somewhat of a contradiction. You're wondering why the engine only reaches 4000 rpms AND you state no reason to believe the engine is over propped. Perhaps there is a language barrier here, as you noted you're from Denmark.

Just know that max rpms below the engine spec rpm range IS associated with an over propped engine. I'm not implying this is the reason why you're only able to reach 4000 rpms. I'm only responding to information you've provided. There is much more information you haven't posted that would assist you with working through this low rpm issue.

 

[99yam40]

the motor has to produce the rated HP to turn the prop upto the rated RPM. the higher the RPM the higher the HP out put is.
so either the prop is wrong or the motor cannot output the HP to reach the RPM