Proper WOT RPM's on a 86 Evin V6-150

[TopNotch]

Just wondering what the WOT RPM's should be at on an 86 Evinrude V6 150...<br /><br />I have a 21' Barcone C/C. Its a real light boat, fast out of the hole. It tops out at 5200rpm/45mph.<br /><br />I feel like I can sacrafice some acceleration as it jumps out so fast the bow doesnt come up. So perhaps I could squeeze out more top-end with higher RPM's... What do you think? Thanks in advance.

 

[TopNotch]

Re: Proper WOT RPM's on a 86 Evin V6-150

Im looking to get it up near 50mph... Perhaps a change in prop, will help me out. I will report the pitch and diameter of my current prop, when I get out of the office.<br /><br />My prop is SS but it has its edges roughed up a bit. Could that noticeably decrease performance?

 

[Hooty]

Re: Proper WOT RPM's on a 86 Evin V6-150

I think you could spin your engine another 600-650rpm so going down in pitch would be the ticket. As a rule of thumb, one inch of pitch has about a 200rpm effect on the engine, so if you went down three inches in pitch you'd gain about 600rpm. Keep us posted.<br /><br />c/6<br /><br />Hooty

 

[TopNotch]

Re: Proper WOT RPM's on a 86 Evin V6-150

Less pitch would give me less travel per turn of the prop. So wouldnt that make me go slower?

 

[Dhadley]

Re: Proper WOT RPM's on a 86 Evin V6-150

I would suggest playing with the set up before spending money. If possible, raise the motor to increase the X dimension. That will reduce drag and increase rpm as well as performance. <br /><br />Test and let us know how you make out.

 

[TopNotch]

Re: Proper WOT RPM's on a 86 Evin V6-150

What would a smaller diameter prop (same pitch) do for me?<br /><br />I feel that the height of the engine is dead on.

 

[Dhadley]

Re: Proper WOT RPM's on a 86 Evin V6-150

Usually a smaller diameter will require a lower X dimension. With the lower X dimension, if required, and less blade area the "bite" may not be as good.<br /><br />This is all considering that you are comparing two props that are the same as far as material, rake angle, cup and length of cup, style of blades etc.

 

[TopNotch]

Re: Proper WOT RPM's on a 86 Evin V6-150

Wow, a whole lot to consider... Well I suppose I'll take your advice on using a prop with less pitch and see how it goes... Thank you very much! Ill post back with my results, sometime in the next week.

 

[njcowboy]

Re: Proper WOT RPM's on a 86 Evin V6-150

less pitch normally means less speed on the top end.<br /><br />I had to drop to a 13 pitch from a 17 pitch and lost 4 MPH, but I would rather loose the speed than damage the engine.

 

[Dhadley]

Re: Proper WOT RPM's on a 86 Evin V6-150

I recommend dropping pitch only as a last resort or if the pitch was WAY off to start with. We would rather work with the set up to gain rpm rather than have engine life and performance suffer.<br /><br />Good luck!

 

[TopNotch]

Re: Proper WOT RPM's on a 86 Evin V6-150

So you think i should be happy with what I currently have? And not change anything.<br /><br />I do have just a stock SS prop. Havent looked at the pitch/dia numbers yet... (too busy in the office)<br /><br />(Cornering at high speeds, and acceleration are cavitation free)

 

[Dhadley]

Re: Proper WOT RPM's on a 86 Evin V6-150

5200 rpm is lugging the motor throughout the entire range. It will certianly coke up quickly and may die a horrible death.<br /><br />I have 3 crossflow V6's and every one is set up at 5800 to 6000 with an average load. They never coke up and have run for years. Now that I think about it, I cant remember the last time I even changed spark plugs. <br /><br />I dont like to drop pitch simply because 9 out of 10 times you lose speed.

 

[TopNotch]

Re: Proper WOT RPM's on a 86 Evin V6-150

Im afraid that if I start raising up the engine im going to vent the prop. How much higher would I have to raise the engine before I would notice a difference in WOT RPM's?