Where are you located?

Huge red flag. PASS.

Whether the seller is hiding something or doesn't know any better, I wouldn't want to buy a boat from a shady person OR someone who doesn't know anything about boats--means they probably don't know how to take care of one either.

If there's no problem, why object to compression test? If you're buying you should have your mechanic check out the motor from top to bottom anyways.Like someone else said run don't walk away.

Quick question.....

When is the last time you bought a used ANYTHING OTHER THAN A BOAT, and insisted that a compression check be performed before you would consider it?

Honestly....I have never asked.

I've never bought a pre-owned vehicle that wasn't "pre-owned certified" with a warranty. I wouldn't buy a boat without a compression check, either.

I don't see red flags, unless the owner won't let a mechanic check it out, at BUYERS expense,

Is the motor still under warranty? If so, how much is left.
Have you taken the boat out for a test drive? If the motor runs fine and has warranty then I wouldn't worry about a compression check. I would inspect the hull and lower unit for sure. If you don't know a lot about boats and what to look for then have a professional inspect it at your expense. If the seller refuses to allow you to have it inspected then walk away.

Warranty is meaningless if scheduled maintenance hasn't been performed and recorded.

well... There's an important factor here.

Are you offering to pay for the test?
If yes, and he says he does not want to do it... then absolutely, walk away.

exactly.

Shoot, just go buy an off-the-shelf compression gauge at the local parts store and do it right there in front of him. Take about 15mins on an outboard.

I just sold a 2012 boat last week. We did a full Mercury engine report and a compression test. All came back good. The Mercury engine report is very helpful. It will tell how many hours at each RPM range.

+1 on this.

Just my $.02 but if anyone thinks they are going to drag my boat to a shop or mechanic, they are going to put a check in my hand first. There's no way I would let someone I don't know take my boat to a shop/mechanic I don't know. On the flip side of this, if I were to sell my boat, all this would be done by a reputable shop prior to selling it anyhow. If the seller insisted on having "their guy" do it, he has the option of bringing his guy to my boat, or just keep walking. There's too many tire kickers these days to be having to take your boat to every guys mechanic.

run, run, run. doesn't feel rights its probably not right

I would ask the owner if we could do it together. Buy a gauge and do it at the owners place. You want the motor warm so bring a garden hose and muffs. If it is a 2012 and 200hp up that ain't a cheap boat. I would want a look over from a qualified mechanic. I would not have a problem using one he wanted. Reputation is everything for a service company these days. I don't think many shops would risk theirs for a friend. My .02