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-   -   WOT rms seem low (https://www.offshoreonly.com/forums/drives-lower-units/257897-wot-rms-seem-low.html)

Griff 07-16-2011 01:14 AM

Use a good tach and GPS speed and report back. There is no way to make any suggestions without real info.

Bernarde 07-16-2011 08:07 PM

So here's my report WOT new tach read 4600, speed on gps was around 40-43. I am getting 34-35 degrees at full advance@ 3000 rpms. Carb seems to be functioning correctly, although I think it could use some tuning. So any thoughts?

Griff 07-17-2011 01:48 AM

I would try a 17 and 19 pitch Mirage Plus prop.
To calculate prop slip, you will need to know the gear ratio in the outdrive.

Bernarde 07-17-2011 09:43 AM

I think the prop looks a little suspect, the blades seem to be awful thin and the machining is poor at best it does'nt look like it was cleaned up at all when it was produced. So when I can get some funds together I am going to switch props out. Thanks for all the input everyone, I will let you all know how it works out later on.

Griff 07-17-2011 11:40 AM

You can use BBlades test program to try different props.

Bernarde 07-17-2011 07:03 PM

Thats where I figured I would go, they are just down the road from me. And I have heard nothing but good things about them. How much am I going to lose on the top end buy swithching to a 17p? As it sits the best I can get out of it is 45 mph. Also would trim tabs help me with any of this?

onesickpantera 07-17-2011 07:09 PM


Originally Posted by Bernarde (Post 3454408)
So here's my report WOT new tach read 4600, speed on gps was around 40-43. I am getting 34-35 degrees at full advance@ 3000 rpms. Carb seems to be functioning correctly, although I think it could use some tuning. So any thoughts?

You're down on power. A 221 Lib with a 330hp 454 runs 55-57mph.

Bernarde 07-17-2011 09:30 PM

See thats where I'm at a loss, a friend of mine has the same boat with the same running gear and he is running in the low 50's. I'm not sure about the prop he's running though.

Griff 07-18-2011 12:57 AM


Originally Posted by Bernarde (Post 3454883)
Thats where I figured I would go, they are just down the road from me. And I have heard nothing but good things about them. How much am I going to lose on the top end buy swithching to a 17p? As it sits the best I can get out of it is 45 mph. Also would trim tabs help me with any of this?

You should gain top end speed. You will get more rpms and the propslip should go down. Your drive is relatively deep by todays standards and the 4 blade prop is probably holding you back.

Bernarde 07-18-2011 04:41 PM

Griff, current setup is a 3 blade but like I said I dont think it is in very good shape. The blades seem thin and the hub surface is somewhat rough. So just to clarify, your saying that a good 17p 3 blade is the direction I should go? Also the carb is only 600cfm, would switching that out to a 650 with a mechanical secondary help at all?


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