115 & 150 evinrude compression issues

[bigdawg10132009]

couple questions folks.......

i have a 1979 115 evinrude with compression numbers of 100, 100, 95 and 90.... i am gonna run some seafoam or deep creep? through and see what happens.....

i checked the compression on the 150 evinrude i got with the nice project boat i bought and the readings were 85, 80, 75 and 60......i am gonna take the plugs out, run cleaner through everything and see what happens. the motor set up for a while and they ran it last summer after a loooong period of sitting up. i ran it with gas mixed with mucho oil to help prevent damage to cylinders due to dry run........

is there a site where i can get the compression specifications for my engines???? thanks.

[pistnbroke]

with two strokes they are not too specific on actual pressure more on being even the 115 does not sound too bad for an old motor though the cylinder with 60 on the 150 needs looking at ...but if they are old and run reliably why not just run them and enjoy as they are not worth much .....

[bigdawg10132009]

thanks pistn......
i may try to decarb and see if the rings are in need of decarbonizing.......deep creep will be used......
any advice on a good way to use it or just follow the cans directions?

[pistnbroke]

sorry they dont have deep creep in australia so go with the can ...

[powerabout]

what year is the 150
If those lower compression readings are on one bank on the v4, I would mill the head down to make them the same.

[bigdawg10132009]

its a 1984 model but i did not have all of the plugs out nor wot.....

[Frosty]

Originally Posted by powerabout

what year is the 150
If those lower compression readings are on one bank, I would mill the head down to make them the same.

WHAT? You must be Joking,

[pistnbroke]

yes Frosty I agree an idiot (The number of times I agree with Frost is firightening ..I must get a life)

when you test the compresion you need all theplugs out BUT YOU MUST NOT PULL OVER WITHOUT THE PLUGS ON THE LEADS AND EARTHED OR YOU WILL FU@@K THE SWITCH BOX .........BEEN THERE DONE THAT ....EXPENSIVE

[powerabout]

Guys

OMC recommended this to their factory trained technicians of which I guess you 2 are not.
I think there was even a service bulletin telling you how to measure the amount.

I would love to know why not and you better tell the guy is who currently the national service manager for BRP OZ he doesnt know what he is talking about as he taught the classes.

[pistnbroke]

yes powerabout what you are talkingabout is in production pre sale just like balancing piston weights and dimension during assembley to take out production tolerances ..,,,no doubt he has a selction of heads and gasket thicknesses to do this ..certainly not something you do when the motor is 20 years old ...and if the head covers 3 cylinders how do you machine the just one .....??????

[bigdawg10132009]

ok pistn.....i will put the plugs on the leads and ground them to the engine.....
i put the liquid form of seafoam in the cylinders about two days ago and let it sit.....i will fire it up this week and run a can through the carbs as well.....i am suspecting i may need to take the carbs off to clean the bowls eh? there is a little build up in the bottom of the filter.....

[Frosty]

Powerabout adjusting the heads with gaskets to balance the compressions on a new engine is not meant to bring back compressions on an old engine.

His rings are shot/ worn or well down the road, skimming the head will do nothing as thats not the prob is it?

And niether is there such a thing as "mechanic in a bottle".

[pistnbroke]

Well frosty and I agree again !!!

Leave the carbs alone at present if its running and sort out the compressions .....you may find your foam has made no difference if its worn rings but if one was stuck and is now free thats different

all plugs out and WOT crank on each cylinder until pressue peaks on the gauge .....

[powerabout]

They dont adjust the heads or gaskets on the production line ( but I guess you have never been seen an outboard producton line) thats why many V4's had different comp on either bank especially on the higher compression engines like 115 and 140's. The heads are sand cast and different parts left to right.
You will probably fnd the engine had the same difference in comps from new as many did as I have checked many new engines of that era.
It was common for 10 to 15psi difference between banks.
Even funniert to see a shady tree mechanic rebore, new pistons an rings and get the same difference after the rebuild as before.
It happened many times. The shady tree mechanic always trying to apply automotive knowledge to an outboard...never works.
The 140's were the worst as they had the highest comp ratio. This caused rough idleing and one head to run cold so the fix was to measure to the deflector crown and then machine the difference off the head.
It made them run much better thats why OMC recommeded it and would process a warantee claim for it.
You have noticed outboard manufacturers dont usually publish compression pressures...

If you have one low cylinder on a v6/v4 you have another problem as the rods and pistons beng the same part have far less chance of being different. 60psi sounds like a broken or stuck top ring to me so I would investigate that straight away.
150 V6 had fairly low compression heads as they were meant to be a work horse engine with its 1" carbs. It made a nice engine.

There you go..todays lesson for the shady tree machanics.
Now do you want to know how to do a quick check of the rings in a cross flow?

[Frosty]

Originally Posted by powerabout

They dont adjust the heads or gaskets on the production line ( but I guess you have never been seen an outboard producton line) thats why many V4's had different comp on either bank especially on the higher compression engines like 115 and 140's. The heads are sand cast and different parts left to right.
You will probably fnd the engine had the same difference in comps from new as many did as I have checked many new engines of that era.
It was common for 10 to 15psi difference between banks.
Even funniert to see a shady tree mechanic rebore, new pistons an rings and get the same difference after the rebuild as before.
It happened many times
The 140's were the worst as they had the highest comp ratio. This caused rough idleing and one head to run cold so the fix was to measure to the deflector crown and then machine the difference off the head.
It made them run much better thats why OMC recommeded it and would process a warantee claim for it.

If you have one low cylinder on a v6/v4 you have another problem as the rods and pistons beng the same part have far less chance fo being different.
There you go..todays lesson for the shady tree machanics.
Now do you want to know how to do a quick check of the rings in a cross flow?

So you've been on a tour round an outboard motor factory and now you know everything.

They DO adjust compressions/ clearances, (pistons on some engines protrude from the cylinder) with different coded gaskets. I dont know about cheap nasty throw away outboards but bigger engines do.

Don't call people shaded tree mechanics without knowing what or to who you are talking you'lle get bitten.

You have already burned any reputation you might have had by a ridiculous suggestion, but I guess it was'nt so ridiculous to you.

You are not a mechanic ---I know you are not.