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Antenna Tuner ?



Here is the situation...


I have a N9TAX dual band antenna, 40ft above ground (20' above my roof) Fiberglass mast. 25' run of lmr400 and a pair of mix 31 and mix 61 snap on ferrites All UV and weather proofed.  Access to adding an antenna is difficult.  Swr is good on gmrs and murs.


My brother has a fishing boat. I have an Icom marine radio, when I use the radio on the antenna, ship to shore channels, SWR is above 3.


I recently picked up a winning bid (on line) for a MFJ-921 VHF 144-220 MHz. Antenna tuner- $50.


There are a lot of opinions on forums, about, not using a tuner on upper vhf bands....most opinions are to just properly tune your antenna since mismatched feed lines and large antennas aren't an issue on that portion of the vhf band. But not really addressing any problems that might be incurred if actually tried.....


The icom marine is only 25 watts and the swr isn't too high, but I still would prefer not to punish an expensive radio on high power... To my knowledge the tuner just matches the impedance at the end of the feed line within the radio's tolerance. Which is all I am looking for -protection. I know swr doesn't per se, effect performance.   

I believe the loss going through the tuner is around .5 db.....


Any opinions on this idea? Before I get started with this experiment.... MFJ-921 is a manual tuner.

Plus I am studying for my Ham ticket, so if this is an option, it might save me a dangerous climb to add/replace antennas. And I would like to keep my gmrs repeater for my family..... 


Please and thank you, in advance for any opinions, knowledge, expertise that you can give me in this endeavor.


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Admittedly I know little about tuners other than they fix the impedance mismatch. It will NOT fix SWR due to antenna mismatch, and can still cause issues with equipment. This is why we must still roughly cut antennas to a particular band before using it. Easiest way to explain it is to watch an elmer talk about tuners. https://www.youtube.com/watch?v=ibAIDNcPKh8

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