PSI/Dyno??

[flippinstick]

When a marine mechanic hooks a boat up to a dyno and says, This motor needs to produce an X amount of PSI. What exactly does PSI mean. If a motor is freshly rebuilt but the PSI is low on the Dyno, what are the possible reasons why this could be?

[flippinstick]

Anyone?

[DaveR]

Not quite clear on the question Dyno readings are usually in HP, when you talk PSI and outboards you are usually referring to Cooling Water Pressure. 12-15 PSI is as low a water pressure value as I would ever run a Mercury at WOT (wide open throttle) for any length of time. Maybe water pressure is not up to snuff and worried that overheating will occur, he is smart not to run it. Low H20 Pressure readings are a whole nother issue. if the motor is out of the water it could depends upon the water inlet source, ear muffs water tank? Or maybe the waterpump impeller has taken a set and isn't moving water efficiently or its not working at all. You're not gonna see real high pressure until you give it some RPM. Good Luck and don't dyno a fresh rebuild, let it break in properly first.

[DaveR]

I probably missed the mark with my previous post.
I did some searching and found this quote in some literature for a dynamometer.." using a toroid water brake absorber. Loads most high performance engines at any throttle setting or RPM you need to test at - indefinitely! (Requires minimum of 5 g.p.m. @ 30+ p.s.i. for every 100 continuous Hp" ...
So I ain't qualified to correctly answer your question. Cut and paste this link into your browser and if it don't help ya post a question on that board and those guys will get your answer.

http://www.wmi.org/sql_messages_html...ni&num=28508#5

[fishhunter]

go to this websiteand ask them they really helped me once before www.ganotech.com they will give you the low down happy huntin, the hunter

[MarkW]

PSI----is pounds per square inch, which is referring to pressure--more then likely water pressure. Dyno's are a great tool to load down an engine and give an accurate horsepower reading to tell if the engine is producing what it's supposed to.

[flippinstick]

The motor was built almost a year ago and SOMEONE put this on a dyno and said the PSI was low. THEY said the problem has to be internally and no possible way on the outside. They took the heads off and said it all looks good, it has to be on the outside. Didnt make any since to me and I still have a under powered motor. I was curious to see if anyone else has had any expirence with a dyno.