so I did a test on a boat I was looking at and I didn't start the motor (i.e run it with muff's on the lower unit). every test came back the same on each spark plug that was pulled. Is that a good enough reading if they all check out the same?

if it is a used boat take it to the lake an run it to make sure everything is ok it will save you a lot of misery. if the current owner wont allow that move on to the next deal.

ssmith gave you good advice. By checking compression you checked for what could probably be the most expensive and most serious problem (bad cylinder / power head), but there are still several factors that you want to eliminate by running the boat.

Running the motor without testing compression is (in my very unprofessional opinion) more dangerous than checking compression without running the motor so if you buy the boat without running it you may not have the expense of a new power head in your very near future but there could be less expensive but still serious issues.

A boat can appear to run fine even if it is beginning to have a weak cylinder. That's why the compression check is vitally important.

Good luck to you! I've helped almost 70 people buy a used boat since 2008. I don't flip them nearly as often as I used to, but I learned three very important lessons:

1) If you can't check compression then walk away.
2) If you can't run the motor then walk away.
3) Follow your gut when reading people. Good ol' boys are easy to spot and so are "smooth talkers".

Feel free to holler if there's anything I can do to help.

-Bryan 979-595-8410

I also like to be there when the person starts the motor when they put it in the water. I don't want to buy a boat that you have to pump this twice while standing on one leg, then turn the key once while pushing in for five seconds, then do this, then that to get it to turn over. My buddy bought a boat like that and when he talked to the previous owner he basically said it's always been that way. It was a real pain in the butt to start no matter how long it sat - one day, week or month.

I agree with what's said.

I've always stuck to used boats.

If they will not allow compression test, lake test, and mechanics inspection walk away.
If they do not have clear titles to motor and hull walk away.

If it will not start walk away unless you get it checked out and know what it will be to get it lake ready.

It's best to just have a mechanics inspection done on it, some do it free and some charge, best money you can spend.

Also, don't just have it run on muffs out of the water. Lots of outboards with issues will start and run on the muffs, but as soon as you put them in the water, they won't start, or stay running at idle. The difference is back pressure is not present when running on the muffs.

Also, the correct way to do a compression test.
1) operate motor to get it up to full operating temp (can be done on muffs)
2) Battery must be fully charged
3) remove ALL spark plugs.
4) open throttle to wide open (in neutral) so butterflys are fully open.
5) keep a battery charger on the battery if possible...... to keep the cranking voltage up
6) Do not spray or apply any oil or lubricants into the cylinders.
7) attach compression gauge
8) crank motor so that there are a minimum of 3 compression strokes on the Cyl being tested, up to a max of 5.
9) record the reading
10) release the pressure on the gauge
11) move to next cylinder and repeat steps 7 thru 10
end) compare readings to OEM specs for cranking pressures.... just beacuse they are all within 10% of each of the other readings is not the only pass/fail test. you could have a very worn out engine that all cyls read close to each other, but are way below the correct cranking pressures.

but ALWAYS do a lake test as well..... hopefully with a full load in the boat (bring a few friends for balist)

ya forgot one thing.... if not usin' remote start button and usin' tha key ya need ta ground all spark plugs and/or plug wires..........

just let the wifey hold em.

tried that with tha first two!.. they didn't see tha humor in it....