compression test

bobkyle2 · Oct 2, 2010

so i ran the compression on my 84 mercury 150
#1-121
#2-122
#3-119
#4-124
#5-121
#6-125

after i ran them i realized i didnt have the throttle wide open... it was in nutreal... would that affect anything... and if it would would it hurt the numbers or help.... i talked to my dad and he said the numbers sound good... what do you guys think...

i did the compression test becouse today when i put the boat in and it barely start... i had to keep cranking intill the batterys were almost dead but it finally started it was missing at idle and when i took off.... but it cleared up...it was also 69degrees today

when i pulled the plugs they looked gas fouled...(just replaced them about a month ago with ngk i beleive the part number was BU8H) ...

another question does these motors an air filter....
after it cleared out it ran good but still felt like it was missing a little at idle

86 century · Oct 2, 2010

Re: compression test

Sounds alot like my '81 200. It may have been not enough fuel mine starts like that at 90. Just choke the hell out of it and use huge batteries.
Good Luck

bobkyle2 · Oct 3, 2010

Re: compression test

i filled up with gas the other day and then realized i didnt have oil so i looked all over the town i was near for quicksilver or penzoil OB 2stroke oil... but coudnt find anything like it... but finally found valvoline 2stroke oil... said it Mercury outboard approved....... and thats when all this issue started.... and its smoking alot more and it smells way different... so im going to flush all that gas out and change plugs again i guess...

Hopefully i can get a nice warm day to take it out again ... its 64today

Faztbullet · Oct 3, 2010

Re: compression test

Your numbers are close so throttle is no issue and no air filter....

starcraft1982 · Oct 3, 2010

Re: compression test

I dont really know the history of whats been done so heres just some thoughts.I would invest in an adjustable spark gap tester and verify good 7/16"spark to all cylinders.Sounds like you could be short one or two.If that checks ok,then you would be left to explore fuel delivery.You could have dirty carbs.Even IF theyve been recently cleaned/rebuilt,you could have crap in your tank getting sucked up or you could have deteriorating fuel lines and/or primer bulb causing debris to get into carbs.Either way,if spark checks good,thats the next area to investigate IMO.good luck

bobkyle2 · Oct 4, 2010

Re: compression test

thanks alot guys..

ive replaced all the fuel lines from tank to engine... going to replace the lines under the hood to.. and still need to replace the bulb..

my owners manual is at my camp a few hours away... i was wondering what the lines that go to each cylinder are... they look like small vacuum lines.. one of them look sketchy should i replace just the one or all...

bobkyle2 · Oct 4, 2010

Re: compression test

been doing a little reading online and can someone take me to school on them lines..i guess there called bleed lines????... or do i need to man up and drive 3 hours and get my manual...haha ive read alittle bit and i think i could have a problem... theres some oil under the cowling of my motor and have yet find out were its coming from and i think it might be coming from one of those lines...... my engine was oil injected but all that is removed and there is a block off plate .... sorry guys its not a chevy... im lost with outboards

jerryjerry05 · Oct 4, 2010

Re: compression test

Replace all of the lines.They are return/bleed lines.Possible air leak.
Possible you got some bad gas.Valvoline oil shouldn't be a problem.
I'd guess since it's an older outboard Ethanol is messing with your hoses and gas lines and carbs.Read my signature.J

Chris1956 · Oct 4, 2010

Re: compression test

Bob, Normally you need to choke the heck out of the motor to get her to cold start. Do you have choke plates or an enrichener on that motor? Hold the choke button and see if it works.

bobkyle2 · Oct 4, 2010

Re: compression test

thanks alot guys...
can anyone tell me what these lines do and why we need them??..

i will replace these lines hopefully sometime this week and hopefully get to take it out this weekend

and chris ... i have the enricher... and i have choked the snot out of it... i think it was actually flooding it...

jerryjerry05 · Oct 5, 2010

Re: compression test

Leak air into the fuel/oil system.It could suck air.Making it run lean.
Like I said before you need to check for ethanol damage.It can:melt the inside of hoses and clog the pump/filter,make them soft and collaspse,make the diaphram weak and put holes in it.The needle/seat clogged or plugged.
Do a spark test.Use a gap tester.$6 at Auto Zone.Should be about 7/16".J

J Hartman · Oct 5, 2010

Re: compression test

bobkyle2 said:
i filled up with gas the other day and then realized i didnt have oil so i looked all over the town i was near for quicksilver or penzoil OB 2stroke oil... but coudnt find anything like it... but finally found valvoline 2stroke oil... said it Mercury outboard approved....... and thats when all this issue started.... and its smoking alot more and it smells way different... so im going to flush all that gas out and change plugs again i guess...

Hopefully i can get a nice warm day to take it out again ... its 64today

different oil can produce a different smell. It doesn't neccesarily mean it's bad. . . I ran the super tech wal-mart stuff in my jon boat forever and ever, and my dad was testing out using some other oil. evinrude XD-100, To me it smelled like my little jon engine was about to catch on fire or something, but it was just the difference in the detergents in the oil. You have to remember there are viscosity differences in the oil, and that some oil is made to be blown "injected" directly into the cylinder, while other oil is made to "premix" IE the differnce between Evinrude XD-50 and XD-100, Most older engines would run the XD-50, While the newer "optimax" style injection would prefer the XD-100

Hope that made cents. =)

Chris1956 · Oct 5, 2010

Re: compression test

J Hartman, Just so you know, Direct Injection motors do not inject oil into the combustion chamber. Oil is introduced into the air intake stream via the throttle bodies. Air and oil make their way into the combustion chamber via the transfer ports, like in a conventional 2 cycle motor.

If oil was to be only injected (blown) into the combustion chamber the crank and bearings would have no lubrication.

bobkyle2 · Oct 5, 2010

Re: compression test

jerryjerry05 said:
Do a spark test.Use a gap tester.$6 at Auto Zone.Should be about 7/16".J

thanks for the info

starcraft1982 · Oct 5, 2010

Re: compression test

You`re welcome!!! Geesh!

bobkyle2 · Oct 5, 2010

Re: compression test

haha..Thank you all for the info..

might be a couple days before i can get to it...

bobkyle2 · Oct 6, 2010

Re: compression test

well looks like its going to be in the mid 80's this weekend... so hopefully me and the my boat can go fishing...and my girlfreind can come too

...

hopefully the new plugs and new bleedlines will fix my issues...

bobkyle2 · Oct 7, 2010

Re: compression test

got the ignition tester last night... so will also do that friday morning

j_martin · Oct 7, 2010

Re: compression test

Bob,
Couple of sleepers that I have seen.

1. Enricher, choke, and it's operation. On my 88 with the dribble enricher, I hit the "choke" for 10 seconds in cool weather before I even crank it. Then with throttle lever half way up, and cranking while choking, it usually hits within a second or so. With butterfly chokes, check that they are fully closing, and crank with choke relentlessly till it fires. Still shouldn't take over 10 seconds.

2. These engines had fuel lines that ethanol hurts. Age also hurts them.

3. Cranking speed/starter current. This one bit me, the "electric system expert" enough so I junked a perfectly good battery and bought a lesser one for 80 bucks at a marina. These starters build up debris in the brush end that partially shorts them. It's pernicious, and sneaks up on you. Starting current should be about 125 amps or so. If it's 300, there's the problem.

hope it helps
John

hope it helps
John

bobkyle2 · Oct 7, 2010

Re: compression test

Thanks john.....i think i had fouled my plugs... an or a plug wire bad... all my carbs looked great... thought i had one leaking but i believe it was a bleed line..

i was going to make up a set of new plug wires for it ... is there any reason why i cannot use like automotive spark plug wires.... i make all my own wires for my race trucks... but i thought i remembered reading the wires are different i just cannot find it in my manual...

compression test

Petty Officer 2nd Class

Ensign

Petty Officer 2nd Class

Supreme Mariner

Petty Officer 1st Class

Petty Officer 2nd Class

Petty Officer 2nd Class

Supreme Mariner

Supreme Mariner

Petty Officer 2nd Class

Supreme Mariner

Petty Officer 3rd Class

Supreme Mariner

Petty Officer 2nd Class

Petty Officer 1st Class

Petty Officer 2nd Class

Petty Officer 2nd Class

Petty Officer 2nd Class

Admiral

Petty Officer 2nd Class