If he`s good, reputable and gets it running correctly
$1100 seems like a good deal.

I would pick octane requirement over ethanol free 90. From 1999 - 2017 my Mercury 280's and then 300xs had no issues on current ethanol fuels. Since then my boat only needs 87. That's my opinion! BTW... there are some land gas stations selling 90 ethanol free octane for $4.60 last season.

Without an invoice/estimate with a cost break down of exactly what he is doing, it is hard to tell.

https://www.mercuryracing.com/produc...erndrives-faq/

https://www.offshoreonly.com/forums/...erc-525sc.html

No vacuum/boost gauge?

I remember back in 92 was crucial to run no less than 90/91 octane per merc. I believe it was because it was early on and they loosened up a bit with 525 SC. And yes they did run pig rich set up from the factory.

The 525SC was 92 Octane required by Merc. Lots of people did post that they had run 91 regularly though and a few said they ran 89 in a pinch.
The 575SCi was 91 Octane required by Merc.

The reason for 90 oct s Ass nd non ethanol is that my tank is aluminum . Do not want corrosion

If you do have a mechanic do your work be sure tell him you would like to have the parts that were replaced. Sounds like your basic maintenance. Did he do a leak down? Would suck if you got it back with same issues. Might be time to replace items mentioned regardless but I'd like to get a grip on what exactly is the problem. You can check the plug wires with an ohm meter. Can easily remove cap and clean it up and check for a crack. I just hate when a mechanic will say it needs all this and that and after all said and done your still back to square one. You can inspect plug wire easily look for any arcing. Nice to do at night as you can see arcing very quickly. My best guess would be timing or carburetor,. It least your moving forward anyway. To bad you don't have a twin brother to this one and starting parts one at time.

I run e85 in my street car. Car will sit for months at a time. Never had an issues with corrosion. My last injector rails were bare aluminum. No corrosion in 5 years when I had them.

Just an opinion from a guy using e85 for about 10 years.

I just opened my fuel tanks..after sitting with fuel from 1994.

Varnish...but still smells like reasonable gas...I was totally shocked...I was expecting skunky old gas smell.
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Aluminum tanks were 100% perfect. Try that 10 10% ethanol now...!!!
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It is possible to anodize the inside of the tank to run ethanol fuels...just gotta find the right shop to do it.