Do NOT put a linear amplifer between the M-802 and the AT-140 tuner! You will blow the tuner for sure.
Also, do NOT put a linear amplifier after the AT-140 tuner. These tuners are made to work
into an end-fed, random-length wire, not thru coax to a linear.
I'm not familiar with the Commander 150. The 1250 and 1250E are great linears, which put out a very hefty signal. Only way I can think of to use them on a boat
would be with a completely separate antenna
system which included either a manual of automatic tuner AFTER the linear which could handle the linear's output.
The goal in designing your system is to ensure that both the linear and the radio
each see 50 ohms impedence at their outputs, and that any tuner can handle the applied power with ease.
I use a 600W linear every day with a random length, end-fed antenna (like a backstay). The exciter is fed to the linear whose output goes to a high-quality tuner (Palstar AT1KM) which has repeatable settings. Output goes directly to the antenna. The ground system needs to be attached to the tuner's ground.