Small Outboard Cylinder Compression Test

[@MrMd5555]

I just tested my freebie single cylinder 7.5 horse the other night that a coworker gave me who said it sat in his shed for 19 and a half years! Had 85 lb of psi consistently after 3 pulls 3 separate times! a thorough carburetor rebuild and clean and she's running like a top!

[@SF-rl7hl]

My 1990 6 hp Johnson compression both cylinders is at 52lbs 55 lbs and starts first pull , runs strong! These old Johnson Evinrude motors will run fine down to 40lbs compression no problem.

[@lightskinxxvvxx7334]

Just bought my tahotsu 8hp from a pawn shop thanks for showing me how to do a compression test🙏🏽

[@gorp27]

Great video with lots of good info. Just wanted to let you know that I recently acquired a 1968 5 hp golden jet that uses a single cylinder Tecumseh 2 stroke that has compression of 90 PSI , starts easy and purrs like a kitten.

[@Alan-megan]

That’s mint condition!!

[@DaveEppel]

MAKE SURE YOU HAVE FULL THROTTLE AND FULL CHOKE ON!!!! I have personally seen 30% psi difference with these two conditions the other way (low throttle, choke off). This is especially true on older outboards I work on (60's and 70's).

[@outboardfixer]

I restore old outboards and it has been my experience that say a 15 or 18 HP 50's evinrude or Johnson will show from 90 psi to 115 psi or even a bit more. I think when you get below 75-80 you will be considerably down in power....BUT full power is not important to some. What IS important, as stated above, is that both cylinders are within 10psi. Big variations means one cylinder has at best rings sticking from setting or it is DOWN HILL from there. Good basic info in this vid AND no rambling....to the point!

[@thisoldoutboard]

Thanks that’s exactly what I am looking for!

[@Indietro25]

You need test compression whit electric drill turn quicker an you get 90/100 psi esay

[@MrMd5555]

@@Indietro25 lol, he actually wants to know the actual practical working compression, not interested in hacks to get inaccurately high numbers to cheat the next owner out of an extra $500

[@mattschannel1502]

Hi I have an issue with an old evinrude 40hp big twin it will only crank when the spark plugs are removed it's a pull start do u know what may be causing this

[@mattschannel1502]

@SuperEmitt i have a vid on my channel of the engine and promble it was like it when I got it iv tried filling the cylinders with would and it drain straight out as the lower unit is removed already iv tried removing the exhaust unit but screws started snapping

[@tullysika]

you should do the test with the throttle wide open.

[@bluesteelworx]

That's a relief, my 3,6 hp Chrysler has 70 psi. I was just going to start tearing it down till I saw this.

[@jeffreyhowarth7850]

The reason why the compression is so low is because you have to do a compression test on a warm engine and you will get a higher compression.

[@EastKYEDC]

I have a 6hp Johnson it has 70-69 but it’s a cheap gauge from autozone fires right up just needs some carb work, you think that’s decent enough before I start putting money into it

[@floridamansgarage8629]

I bought a little 64 5.5 today for 50bucks compressions at 70 exact for both couldn’t be happier now the bass better watch out cuz I’m coming

[@johnpower8356]

I always use wide open throttle for comp. test it makes a big difference, try it

[@mumbles552]

All good but it's a good idea to ground the spark plug leads while doing this so the coils won't get damaged from the high voltages being generated. ☺

[@blakethesnake1555]

How do you ground the spark plug lead? And is there a risk of shock if your touching the lead while pulling. Thanks

[@mumbles552]

@@blakethesnake1555 To ground the plugs, I made up some brass rods which snap into the plug boot and have a wire and an alligator clip fastened to them. The alligator gets hooked onto a good ground so the high voltage has a path to follow. A small bolt or even a nail could probably be used instead.

[@The314moses]

Great video, thank you!

[@aydenmcclara4145]

What is the normal compression on a late 90s 25 hp Mercury outboard motor

[@thisoldoutboard]

Above 90 psi when warmed up

[@gustavolizarraga4322]

my outboard is a 1971, 9.5 HP evinrude, and has 35 psi even on both cylinders, any suggestions will be appreciated, thanks. Points and plugs are new, I just bought the outboard a few months ago, it was all disassembled, but complete. I checked and gave a service to the gear case, water pump, coils, and it runs fine, but I feel it king of slow. by the way, good vid.

[@thisoldoutboard]

Make sure your compression tester has the shortest length hose as possible to get the best reading. If you think 35psi is the best reading you can get that’s not good. Does it crank easily?

[@gustavolizarraga4322]

@@thisoldoutboard yes it does crank easily, I will try with another compression tester as you recomended. One thing I noticed when I started it the very first time, was that at the bottom of the water tank I put it in for testing, had some kind of debris, like small pieces of hard carbon, not metal, beacuse I was able to crunch them. I´m considering cleaning the power head, like the ring´s grooves and all the stuff in the way. The previous owner didn´t know how much use this outboard had, but I think it was abandoned disasembled in the lower unit only, for at least 20 years. It has zero corrosion, no salt water use. Thanks for your advise. and.. well.. we don´t know what is gonna happen next, right?

[@thisoldoutboard]

@@gustavolizarraga4322 ride the lightning. God speed

[@gustavolizarraga4322]

@mikey joe OK, thanks a lot, by the way, I did as @thisoldoutboard recommended to me, and tested with a better compression tester, shorter hose and read 50 psi both cylinders, just 4 pulls on each one. I'm gonna try again as you recommend

[@gustavolizarraga4322]

@mikey joe 👍 👍

[@Siwashable]

should fuel line be disengaged?

[@nathanwilkins-mn6ou]

I ran one hot I didn't realize it wasn't pumping water I checked compression could I have damaged anything else

[@thisoldoutboard]

What was your compression

[@jshall1000]

I can't start my 6 hp Evinrude. But in plugs but nothing. I did comp test got 60 on both. Not sure if this is right way I had choke open and throttle on fast. And no fuel to engine. Did I do it wrong

[@thisoldoutboard]

That’s low compression. Double check you are getting fuel air and spark

[@jshall1000]

@@thisoldoutboard ok thanks

[@240SSONLY]

silly question... but what if I pull the crank handle and it feels like no body is home? the crank mechanism is not broken, but it feels like there is no resistance guess there's no compression eh? guessing the motor ran hot for a while because the water pump was failing

[@thisoldoutboard]

Sounds shot, or your spark plugs are missing...

[@nicstr28]

Check the flywheel and make sure the key didnt shear and just spinning on the crank shaft

[@fixitwise7194]

Practical Adice! Do you see any loss of power on your 6hp at 60psi?

[@thisoldoutboard]

I do not

[@alessandropesce1816]

What is the normal compression for Jhonson/Evinrude 15 hp 2st 1999 old?

[@brandonbill8103]

Anywhere from 100 to 125 90 can get away with but you won't run quite as well

[@christopherford1015]

Have a 4hp mercury an it has 95psi

[@nathanhuitson1418]

I have a Johnson 4hp 1969 it’s only getting 65 psi on each cylinder and it won’t start, I have good spark etc brand new head gasket

[@thisoldoutboard]

Will it start with a little starting fluid? You sure your plug wires aren’t crossed?

[@nathanhuitson1418]

@@thisoldoutboard no, I have put 2 stroke down the head and it doesn’t fire at all, I have had a couple of backfires, and it has fired once or twice, I will check the wires

[@nathanhuitson1418]

It was the wires, thank you very much

[@87GP400]

Thanks !

[@michaelcox5096]

My Evinrude 6hp is 80psi even

[@gregoffenback6910]

The motor needs to be deeper in the water. The water pump needs to be submerged.

[@woodysgarage469]

I've got a 1975 6hp Evinrude (see my channel kzbin.info/www/bejne/qKK6lWutabONntE) I'm only getting 50-55 on each cylinder. It will start right up, but quits after 5 minutes or so. Not finding rings readily available and not sure if it is even worth it. What do you think?

[@thisoldoutboard]

Woody, you can find powerheads relatively cheap on eBay (for instance here ebay.to/2mBKV9x ) I find it hard to think spending $150 on a used but good powerhead is not worth all the rebuild time.

[@woodysgarage469]

Thanks for the link, I have sub'd to your channel.

[@thisoldoutboard]

Woody's Garage thanks. already sub’d to you

[@woodysgarage469]

Thanks. Curious, have you run your engine on the water at all for a prolonged time? Mine was a good runner until all of sudden it would only go 5 minutes.

[@thisoldoutboard]

Woody's Garage yeah it was running fine. I have since sold it