Need a Compression Tester

[NJCoastFlyFish]

I am looking at an engine in upstate NY near albany this weekend, I want to test the compression but I don't know where to get a compression tester- Are they expensive?<br /><br />My other question is, is there anyone in the upstate NY area that can meet me saturday to give the outboard a look around who can test the compression and give me an honest idea of the shape of this engine. It is a 1989 mercury 70hp.

 

[NJCoastFlyFish]

Re: Need a Compression Tester

Just did a search, gonna try and give my local auto shops a call, see if I can borrow one. But how about a mechanic or someone who knows there stuff in the albany area?

 

[timmathis]

Re: Need a Compression Tester

Advance Auto has a loan a tool program. Do you have one close by? if not any auto parts store has them or even wal-mart. Tim

 

[TELMANMN]

Re: Need a Compression Tester

Harbor freight has a couple of outlets in NJ and many more in New York. If one is close then they have fairly inexpensive gauges and other tools. If not close can order.

 

[rodbolt]

Re: Need a Compression Tester

wally world has them in the 20 dollar price range.

 

[Todd Humphreys]

Re: Need a Compression Tester

AutoZone also loan tools.

 

[NJCoastFlyFish]

Re: Need a Compression Tester

autozone it is

 

[Navigator]

Re: Need a Compression Tester

Sears carries them as well.

 

[burnboyy]

Re: Need a Compression Tester

sweet, i had the same question, I have a 1975 merc 850, and the clearence is real tight on the bottom two plugs, i was wondering where i could get a compression tester as well (one that would fit my mercury) oh also, is it a 10mm or 12mm threaded head i need for that motor? or is there only one size i can buy?

 

[surlyjoe]

Re: Need a Compression Tester

Originally posted by Navigator:<br /> Sears carries them as well.

ya, they have a nice one that fits both size plug holes, and has recording and a quick disconnect to make hooking it up easier. I have beat mine mercilessly for 15 yaers and it still works great!

 

[Silvertip]

Re: Need a Compression Tester

Virtually any discount store that sells auto parts will stock compression testers.

 

[burnboyy]

Re: Need a Compression Tester

Just for anyone wondering Wal Mart did not have a compression tester, i found one for $50 at schucks that comes with 10 12 and 14mm adapters, think i'm going to get it, don't really have they money, but i have a lot of use i could probably get out of the tool

 

[koolerb]

Re: Need a Compression Tester

I got the one from Sears, it came with multiple fitings, fit my engine no problem. Weird thing about this one, the pressure reading just keeps going up the more I crank the motor. If the thing is working right it should register the cylinder pressure corectly by the third crankshaft revolution on a three cylinder, right?

 

[CFronzek]

Re: Need a Compression Tester

A really good cylinder will pump up fast. It will give you about 40% of total on the first rev. But you can't expect that on well used motors. I look for 95% of final pressure on the 3rd or 4th rev. If the pressure climbs slowly that's a sign that piston/ring sealing is not there. A decarb may give you some more back but, it won't make an old cylinder new again.

 

[Paul Moir]

Re: Need a Compression Tester

A lot of how fast they'll pump up has to due the the compression tester itself. Like how quickly the check valve opens or how much pressure it takes for the check valve to open. Also, the cylinder size has a lot to do with it. Likely there's no real difference on your triple (or other larger outboards), but on little outboards it can make quite a difference.<br />Really, you just have to get to know your compression tester a bit. They're all different. Try it on as many engines as you can.