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  Report: Bennett M120 Trim Tabs on Outrage 18

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Author Topic:   Report: Bennett M120 Trim Tabs on Outrage 18
acseatsri posted 06-01-2004 07:57 PM ET (US)   Profile for acseatsri   Send Email to acseatsri  
Bennett M120 Trim Tabs are considered oversize for an Outrage 18. They are recommended for 20-23-foot boats. I would highly recommend M120 tabs over the smaller M80 tabs, especially for those of you who run in unprotected or rougher waters. They are 10" wide x 12" long.

I was able to install them over a couple nights after work. The only special tools needed were a 3/4-inch holesaw. (A 1-1/8-inch hole saw is optional, and since they both took the same holder, I bought the 1-1/8-inch for another $6. The total was around $16 at Sears Hardware.) I mounted the tabs approximately 3-inches inboard from the chines. This was as far over as I could go and still be able to mount the actuator without going thru extremes to make a special piece to compensate for the step in the transom. [From this I infer that the actuator base is not mounted on the wooden portion of the trasom, which is the thicker area in the center.--jimh] The [laminate in the] area where the hinge plate mounts is pretty thin, probably around 3/16-inch or so. Therefore I sanded the fiberglass and the hinge plate itself to allow 3M 5200 to obtain a better grip. Four #10 x 1-1/2-inch sheet metal screws are uesd for each side (supplied). I'm going to keep an eye on this area and see if I need to reinforce it- so far so good after 1 trial (more about that later).

The [laminate in the] area where the actuators mount is thicker, probably 1/4- 5/16-inch or so. Again, I sanded the area where the actuator goes to give the 5200 a better grip. You'll use three #14 x 1-1/2-inch sheet metal screws for this. You also need to drill a 3/4-inch hole for the hose and fitting to pass through.

I used a no-kink tube bending bracket at this point (supplied) to form a 90 deg bend to run along the inside transom wall. Hoses were sealed through the transom with clear silicone caulking. I used 5200 on all the screw threads as well. I figure this is a permanent installation, so I don't want anything working loose and tearing up the fiberglass.

The hydraulic tubing supplied was too short for my needs, so I called Bennett and they sent me two 21-foot hoses for just the cost of shipping. (Thanks M. J. Thomas!) Eighteen feet would suffice if I were to do it again. I have a resident 1/8-inch nylon pull rope in the tunnel, so running the hoses thru took a minute—took longer to tape the hoses to the rope than to pull it.

The installation video calls for mounting the pump where it won't ever be submerged. Where do you find such an area on an Outrage besides the console? I mounted the pump inside the right rear side of the console, fairly high beside the throttle/shift cables, a normally "dead" unusable area inside the console. You'll need four #10 x 3/4-inch SS machine screws, trim washers, and nuts instead of the sheet metal screws supplied in the kit.

The rocker switch is mounted to the left of the throttle/shift control on the same surface as the throttle controls. It looks as though it was tailor-made for the switch! The template for drilling with 1-1/8-inch holesaw worked well. It took me two minutes to mount the switch. I'd recommend the extra $6 for the holesaw.

I was able to try the trim tabs out on Sunday. There were 2-3 foot waves on Long Island Sound where I went fishing. I also tried a 17-inch pitch aluminum prop at the same time. Definitely putting the 14.5 x 19P stainless back on. I removed the Doelfin, but not the transom wedges. With the 17-inch prop and tabs at full down position, I was able to cruise at ANY SPEED BELOW 15 knots I wanted—the bow NEVER pointed up. A comfortable speed going head-on into about two-foot chop was 10.4 knots at 2400-RPM with approximately 450 lbs. on the leaning post, 10-HP Honda kicker on a starboard bracket, and ABSOLUTE FULL FUEL LOAD! I was never able to do this with the Doelfin, but I didn't have the 17P on either, so I'll have to try the 19P prop next time. My guess is that there won't be much performance difference since the boat rode nearly flat at all speeds. Above 15 knots or so, you have to exercise caution. Too much tab will cause chine walk and the boat to list heavily to one side or the other. An added benefit of the tabs is the ability to compensate for uneven loading. All in all, the investment was worthwhile for the area I use the boat. The other option I have—not sure of yet—is to remove the transom wedges. They cost me some tilt range when in the water. I can't tilt the engine fully out of the water with them and the hydraulic steering cylinder on the front of the engine.

I'll report more findings after further testing.

jimh posted 06-02-2004 01:47 AM ET (US)     Profile for jimh  Send Email to jimh     
Thanks for the excellent report. It is very interesting to hear about the improved ability to maintain the boat on hydroplane at lower speeds.

Did I correctly infer that you have mounted the tabs quite a way outboard so that the base of the actuator units is located outboard of the thicker, wooden reinforced area of the transom?

acseatsri posted 06-02-2004 05:43 PM ET (US)     Profile for acseatsri  Send Email to acseatsri     
Yes, I mounted them far outboard where they didn't land on the wood-filled area of the transom. I am a little uncomfortable with it, but we'll see as time goes by how they stand up. If needed, I'll do the allen wrench trick in a drill to hollow out an area inside the transom where the screws mount, then inject some West System epoxy into the void. The area where the actuators mount is pretty thick (1/4-5/16"), and very close to the wooden area of the transom. I think the actuator bears the brunt of the load when underway, with the hinge bearing a much lesser amount of pressure.
As far as being on plane at 10 knots, I'm not really sure I would call it "on plane", but the boat was definitely riding at the same attitude as when I'm on plane, and it definitely kicks @ss at this speed where a boat without the tabs would be pointing at the sky and pounding you to death. Like I said, the bow never really rose with tabs in the full down position.
JohnJ80 posted 06-02-2004 09:11 PM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     
I don't think you will have a problem with the mounting. The forces on the screws are shear - that is along the surface of the transom and perpendicular to the long axis of the screw.

The one exception to this would be if you were to back down very hard and very fast with the tabs full down. then the force would be longitudinal to the scews and could pull them out.

I had a lot of conversations with Bennett and Lenco about this and they have both mounted these on lots of whalers without any problems.

Next time you have her out, try getting the boat trimmed right, then adjust the trim angle on your power trim until the steering feels effortless. I think at that point you pretty much have the helm properly balanced and the boat trimmed properly. I have been using that as a gauge recently and I think that is when I feel the boat is optimally trimmed. I'd like to hear what you think.

I would also bet you can get rid of those transom wedges - heck, I'd think you'd want to!


acseatsri posted 06-02-2004 09:30 PM ET (US)     Profile for acseatsri  Send Email to acseatsri     
My steering is always effortless and doesn't budge unless I move it. My, how I love hydraulic steering! :)

And yes, I'd really like to get rid of the wedges. They made a big difference when used in conjunction with the Doelfin, but by themselves I just don't see much of a benefit.

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