Having worked for both Mercury and Volvo Penta the general theme to the answers given here have been right on. Both manufacturers recommend external steering as you approach the magic 70mph figure. In a twin installation it becomes absolutely critical (because of increased boat weights usually associated with twins) that you have a more dependable steering system that is rigid and distributes the loading above 65 mph.

Remember that when you initiate a high speed turn with twins and the boat rolls there are different steering loads on the inboard (to the turn) drive than the outboard one. Then when the boat settles there can be another dramatic loading differential. Smooth or flat water this is the case, but rougher water tends to make the rate of the loading quicker. The actual load is a dynamic of physics (speed and boat weight).

There is no substitute for being too safe. If you consider yourself a safe high performance boater you will make the investment. The Full system is much better because it will help stabilize the drive more in case of a component (gimbal or mount) failure.

Good Luck and safe boating!

I have the full IMCO from the helm to back of boat. Should have done it a long time ago!!

My marine mechanic recommended speed around 70 and above.


:D :D