Installing trim tabs on a 160 Dauntless
Posted: Wed Sep 12, 2018 10:26 pm
Every boat design is a compromise. For the 160 Dauntless, the designers gave a small boat a lot of beam, a huge 45 gallon internal fuel tank, and lots of storage space. The trade-off was that the boat is heavy for its size. Add to that the fact that the boat was designed in the waning days of 2-stroke engines and then powered by heavy first-generation 4-stroke engines, and you have a boat that's naturally a bit heavy in the stern and very sensitive to weight.
Back in 2003 when "Golden Daze" was new, I added a SE Sport 200 hydrofoil to the lower unit to improve trim after a rough day on the Chesapeake. For some years I thought it was the best modification I'd ever made to the boat. A few years ago I replaced the cable steering with hydraulic, and wondered whether perhaps that was the new best modification. Now I've added Lenco limited-space 4x12" trim tabs, and there is no doubt that this is REALLY the best mod to the boat!
Fig. 1. The SE Sport 200 hydrofoil served us reasonably well for 14 years or so, but it was never great. (Golden retriever photobomb at no extra charge)
Fig. 2. If you're going to drill 18 holes in your transom, you damn well better get it right the first time. In this case, I decided that the ladder wasn't going to clear the actuator cylinder, and I moved the trim tab inboard of the ladder. Lenco recommends that any hull strake be 4" away from the edge of the trim tab, so the shift a bit inboard put the strake right about in the center of the tab.
Fig. 2. Here's the starboard trim tab installed, with the actuator just barely inboard of the ladder. At the time it seemed like the ladder was just going to clear the trim tab blade. I had to drill the holes somewhat over-size as compared to the Lenco instructions; the plywood in the transom is rock-hard and did not easily accept the mounting screws. I wondered whether it was actually WhaleBoard, which really wants to be tapped first, but according to my diagrams it really is wood.
Fig. 4. With weight on the swim ladder, it was crushing against the edge of the trim tab. Ultimately my solution was to add some 1/2" StarBoard standoffs to the swim ladder mounting brackets, replacing the 1-1/4" screws with slightly longer 1-1/2" versions.
Fig. 5. Mechanical installation completed. The wiring was pretty straightforward as well. (Rainbow photobomb at no extra charge)
Fig. 6. Now comes the hard part, or at least the part that's most visible to everybody! I must admit that the trim switch on the throttle was awfully convenient, so I tried to locate the trim tab controller as close to the throttle as I could get. That meant that it's somewhat behind the steering wheel and is not as convenient as I'd like, but on a small center console like this one there's not a lot of choices. I installed the switches with LED position indicators; the switches without indicators are a lot cheaper but if you spent the money for a Whaler in the first place you may as well keep your standards high! Somehow I didn't get a photo of the final switch installation, but it looks pretty much like you'd expect.
The results are fabulous. Minimum planing speed is reduced from 18 mph to about 15 mph, but more importantly, minimum "comfortable" speed with the boat solidly on plane and the bow down into chop was reduced from about 22 mph to 18 mph. She hops up on plane more quickly with a lot less bow rise, and up to about 32 mph the trim tabs do a great job flattening out the ride. Above that speed they're no longer useful, and when fully retracted they have no noticeable effect on boat speed.
My usual casual cruise speed is about 22-24 mph, and with the trim tabs extended "3 dots" I get a nice flat ride that cuts nicely through light chop or boat wakes. An unexpected bonus is the ability to trim port-to-starboard; I guess I never noticed before how shifting passengers changes the lateral trim, but now I can just correct it. The other really nice feature is the de-coupling of boat trim and engine angle; now I can trim the engine for neutral steering effort at all speeds where previously anywhere below 25 mph the down-trim on the engine made turns to the left much more wheel effort than turns to the right.
I did notice that when fully loaded (7/8 tank of fuel and 5 adults) I could not get the boat on plane with the trim tabs fully down; the extra drag was just too much. I had to raise the tabs most of the way until she was up on the step, and then trim her as desired. The 2003-era Mercury 115 4-stroke (with the Yamaha F115 powerhead) is reasonably quiet, very fuel efficient, and has been very reliable, but a torque powerhouse it is not.
Overall, I couldn't be happier with this upgrade and I wish I'd done it years ago. For those of you running a 160 Dauntless and struggling with trim, I can't recommend enough that you go ahead with the Lenco limited-space trim tabs. You won't be sorry.
-Bob
Back in 2003 when "Golden Daze" was new, I added a SE Sport 200 hydrofoil to the lower unit to improve trim after a rough day on the Chesapeake. For some years I thought it was the best modification I'd ever made to the boat. A few years ago I replaced the cable steering with hydraulic, and wondered whether perhaps that was the new best modification. Now I've added Lenco limited-space 4x12" trim tabs, and there is no doubt that this is REALLY the best mod to the boat!
Fig. 1. The SE Sport 200 hydrofoil served us reasonably well for 14 years or so, but it was never great. (Golden retriever photobomb at no extra charge)
Fig. 2. If you're going to drill 18 holes in your transom, you damn well better get it right the first time. In this case, I decided that the ladder wasn't going to clear the actuator cylinder, and I moved the trim tab inboard of the ladder. Lenco recommends that any hull strake be 4" away from the edge of the trim tab, so the shift a bit inboard put the strake right about in the center of the tab.
Fig. 2. Here's the starboard trim tab installed, with the actuator just barely inboard of the ladder. At the time it seemed like the ladder was just going to clear the trim tab blade. I had to drill the holes somewhat over-size as compared to the Lenco instructions; the plywood in the transom is rock-hard and did not easily accept the mounting screws. I wondered whether it was actually WhaleBoard, which really wants to be tapped first, but according to my diagrams it really is wood.
Fig. 4. With weight on the swim ladder, it was crushing against the edge of the trim tab. Ultimately my solution was to add some 1/2" StarBoard standoffs to the swim ladder mounting brackets, replacing the 1-1/4" screws with slightly longer 1-1/2" versions.
Fig. 5. Mechanical installation completed. The wiring was pretty straightforward as well. (Rainbow photobomb at no extra charge)
Fig. 6. Now comes the hard part, or at least the part that's most visible to everybody! I must admit that the trim switch on the throttle was awfully convenient, so I tried to locate the trim tab controller as close to the throttle as I could get. That meant that it's somewhat behind the steering wheel and is not as convenient as I'd like, but on a small center console like this one there's not a lot of choices. I installed the switches with LED position indicators; the switches without indicators are a lot cheaper but if you spent the money for a Whaler in the first place you may as well keep your standards high! Somehow I didn't get a photo of the final switch installation, but it looks pretty much like you'd expect.
The results are fabulous. Minimum planing speed is reduced from 18 mph to about 15 mph, but more importantly, minimum "comfortable" speed with the boat solidly on plane and the bow down into chop was reduced from about 22 mph to 18 mph. She hops up on plane more quickly with a lot less bow rise, and up to about 32 mph the trim tabs do a great job flattening out the ride. Above that speed they're no longer useful, and when fully retracted they have no noticeable effect on boat speed.
My usual casual cruise speed is about 22-24 mph, and with the trim tabs extended "3 dots" I get a nice flat ride that cuts nicely through light chop or boat wakes. An unexpected bonus is the ability to trim port-to-starboard; I guess I never noticed before how shifting passengers changes the lateral trim, but now I can just correct it. The other really nice feature is the de-coupling of boat trim and engine angle; now I can trim the engine for neutral steering effort at all speeds where previously anywhere below 25 mph the down-trim on the engine made turns to the left much more wheel effort than turns to the right.
I did notice that when fully loaded (7/8 tank of fuel and 5 adults) I could not get the boat on plane with the trim tabs fully down; the extra drag was just too much. I had to raise the tabs most of the way until she was up on the step, and then trim her as desired. The 2003-era Mercury 115 4-stroke (with the Yamaha F115 powerhead) is reasonably quiet, very fuel efficient, and has been very reliable, but a torque powerhouse it is not.
Overall, I couldn't be happier with this upgrade and I wish I'd done it years ago. For those of you running a 160 Dauntless and struggling with trim, I can't recommend enough that you go ahead with the Lenco limited-space trim tabs. You won't be sorry.
-Bob