trim tab anode to clear the prop - laser II hits the trim tab

[rmorit01]

I mounted the laser II on my SSV-164 and found out that the 21P laser II is a bit longer than the aluminum prop or the vengeance  21P.  I looked on the interweb and some people use a hacksaw and cut out a notch in the existing trim tab.  Alternatively it sounds like offset trim tabs exist.

This looks like an offset version I found on the west marine website -

Anyone have suggestions for what the best option would be?  Can the trim tab anode be too offset?

[75starflight]

Do you have power steering on your ssv-164? If you do you do no need the trim tab. On Phoenix when I added power steering I put the flat trim tab replacement disc on and threw away my trim tab. Otherwise mercruiser makes an extended trim tab that clears larger diameter props.

[rmorit01]

Do you have power steering on your ssv-164?

No power steering just the cable.

[Hyperacme]

During prop testing I had to use an offset tab for one of the props.
Should work fine.

Should be notches in mount on tab and on cavitation plate to offset it at different angles.
Do some testing with angles to find best "feel" and lowest torque steer.

 

[Jason]

I run a 23p Laser II on my 140 w/o power steering. I cut a notch in my trip tab. Been that way for nearly 10 years now without an issue. The offset trim tab would look a little more professional though. I have zero torque steer though with my modified trim tab.

[Plugcheck]

      Torque or trim tabs have always been somewhat a mystery to me, primarily because there doesn't seem to be one answer to using them.   Not going to hurt anything by modifying your existing tab, just insure at least 1/8" of clearance for a stainless prop, and more like 3/16" to 1/4" for aluminum props to allow some safety margin.   Offset tabs are available, but they seem to require a different angle setting than a standard tab.  May have been prop difference?   The rest is trial and error, set it and give it a ride.   On my 16's, I liked to have a "hands free" feel to the steering wheel at around 3500-4000rpms as this is where I spent most of my time cruising, skiing, or tubing.   Both would pull a bit right at WOT, and a bit left under 2000.    Once you have it where you like it, score a mark so its easy to set next time.  Most drives require their removal if changing impellor. 

[rmorit01]

OK -- I figured out photo hosting on imgur.

This is what it looks like - the new prop is slightly longer, so the blades extend backwards a bit further.

Also, on the laser II i bought the PVS plugs and just put the solid ones in for now, though I have the ones with holes.  Curious if anyone has used the PVS plugs and noticed any performance differences?  Theoretically, the plugs with holes introduce exhaust gas bubbles that help the prop "spin up" faster.

The drive ratio is supposedly 1.98 on the pre-alpha R drives. This test showed no positive impact of using the vent holes. http://www.boats.com/pvs-propeller-test/#.WbCjWdOGNBw

[David CVX-16]

The setback torque tab probably has more area to it to counter the torque. I run OMC Raker and SRX props that have so much torque that no torque tab would neutralize the pull. I use a flat plate and Teleflex no feed back steering and can take my hands off the steering wheel and not have it turn one way or the other.

[75starflight]

Bob, leave the solid plugs in. I tried mine open and the prop caviated like crazy and would not bite.

Oh, I experienced heavy torque steer with Phoenix when I put on the laser II, but the performance out weighed the steering torque in my mind.

[Plugcheck]

     Looks like time for a little creative metalworking.   You could notch, trim, cut as you need to make clearance.   Curious though, have you tried giving it a run without it on there?  Every prop seems to have a different feel, and it becomes largely a trial and error process.  As for your vent plugs, again this is somewhat a trail and error process also.   Some are designed to be either in or out, but many other systems have varying size holes to customize to your application.  Designed to allow the prop to slip during the hole shot to bring the engine RPM's up, the holes are no longer in play at speed as the exhaust simply flows to the path of least resistance out the center. 

Speaking about ventilation holes in props, David, I'm curious to know how your performance is with no exhaust through the prop.   Might be for a new thread, but I also run a small hub Trophy on my CVZ, but its converted to thru hull, so no exhaust anyway.

[David CVX-16]

   
Speaking about ventilation holes in props, David, I'm curious to know how your performance is with no exhaust through the prop.   Might be for a new thread, but I also run a small hub Trophy on my CVZ, but its converted to thru hull, so no exhaust anyway.

With the over the hub exhaust SRX prop, there is a lot of ventilation/cavitation getting the boat out of the water onto a plane, as you can imagine with the exhaust flowing over the hub. My technique is to trim the motor completely down (motor tucked in) and gently increase the throttle. The boat gradually gets out of the water, and at a certain point, the prop grabs water (stops slipping) and then it is off to the races. The SRX 23" pitch has a bit more slippage than the through exhaust Raker props at all speeds, but the SRX has higher top MPH by 1 to 2 MPH over the 22" Raker. The boat goes about 58 MPH with the SRX 23" pitch at about 5,700 RPM. The SRX prop is great for light loads, traveling fast, gripping in the corners, and bow lift.

Some Mercury motor people use a small hub Mercury prop on the large hub shaft and fill the space between the prop and the inside wall of the lower unit case with a ring to prevent the escape of exhaust gases. The boat goes faster because the prop is recessed from the flow of water over the lower unit.

[Hyperacme]

My Laser II was used and came with the "C = Medium" plug and I never tried the other sizes.
My set up is pretty light for amount of HP I have ... about 1200 lbs. boat/motor/gas/me ... and comes out of the hole fine.
I should change to solid plug and see how it works, but most of the time my take off are not full throttle.

After testing a bunch of props the Laser II was fastest and had one of the lowest amount of torque steer.
During testing we had to remove tab to test one of the props and torque steer was so bad, I needed two hands on wheel !

Of course our boats are two very different styles and the only way of knowing what works is testing your set up.
Maybe look into a NFB steering system ...
http://www.seastarsolutions.com/

[CVX Fever]

Bob, leave the solid plugs in. I tried mine open and the prop caviated like crazy and would not bite.

I pulled them out on my Enertia with pretty much the same results. The prop just spun more coming out of the hole without any real noticeable performance benefit.

The trim tab is nothing more than a rudder. Kind of a crude way to offset torque steer IMHO. Either grind away the one you have to fit or buy one made to fit props like your Lazer II.