07-25-2008, 10:19 PM
Just picked up my new boat and motor. Got a 150 opti max. I noticed that it doesn't have a trim tab on the lower unit. Asked the boat rigger at the dealer if this was right and he said that mercurys with power steering don't need the trim tab. Is this right?
07-26-2008, 01:17 AM
Yes it is. I asked the same question 5 years ago on My 175. C-man
07-26-2008, 06:25 AM
....if the boat is not rigged to compensate for steering torque then handling will be poor- and covering it up with low effort power steering won't restore the handling deficiencies. The good news is that most walleye boats end up with near neutral steering torque due to their hull design and load-outs, so it is common to use the Merc zinc plate instead of one of the 2 trim tabs that are available to fit the Optis and other Mercs. The 2 available tabs include the standard tab- which may not clear high rake stainless performance props, and the so-called high performance or off-set tab, which will clear high rake props. Check your set-up by running with a normal load and opening up the boat to about 3/4 throttle with your trim set for best speed without porpoising. Work the wheel left and right to see if you detect if its harder to steer in one direction. If you can't feel much difference, trim in a bit to put the bow down and you should be able to feel what torque steer is like- even with hydraulic steering. Now go back to your best trim setting and check again for any felt torque. Last step is to open to full throttle, again trim for max speed, and check again. In some cases you can eliminate the torque steer just by changing the trim angle a bit- and this small amount may not reduce speed at all. If you notice harder steering to one direction then a tab can be used to remove this torque. If its high, you may even pick up 1 mph or so since you are reducing what is called the crab angle of the engine at speed. If your top speed is over 50 mph and your motor is raised 2-3 notches, none of the standard merc tabs may work, since the tab may be out of the solid water flow at top speed. In this case, you add a skeg mounted tab, available from the aftermarket suppliers. My Starcraft 176SC with 150 Opti is running in the low 60s, motor is raised 3 notches with a high rake prop, and would be downright dangerous without the skeg mounted tab that I run. Even with hydraulic steering I can easily feel the steering torque if my trim is not set correctly.
07-27-2008, 02:32 AM
Thank you. I'll give your directions a try today.