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]

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,:eek: :eek: :eek: :eek:

[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]

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.

[powerabout]

I dont know everything I just spent 10 years working on them and had plenty of factory training on the products mentioned above.

You exposed yourself when stating a procedure recommened by the factory is ridiculous.

You are talking about diesels when you mention piston protusion.

I dont know about cheap nasty throw away outboards but bigger engines do.
Very true on both counts

[Frosty]

Cripes I walk away for 10 minutes and youve posted again, I thought you were on holiday in the Med. you cant be enjoying your self very much you seem to be on here 24 hours a day.

No engine will be equall compression to within 10 --15 PSI,-- that would be good.

Skimming the head on an olde 20 year old engine to bring up a compression is ridiculous.

[powerabout]

OK

If the engine has a reason for lower comp than when it was made then it is a mechanical problem as you say.
I mearly noticed when people post compressions that show one bank lower then the other there is a very good chance it has been like that from new due to the issue I mentioned.
My mistake if I insinuated skimming a head to cover a failing cylinder.
Further investigation is needed but if the rings / bore look good...then what.
And on a outboard 15 psi is getting significant they should be a lot closer.
Certainly would be in a new engine ( but maybe not on the old 115/140 V4's)
There are no valves so its just the rings and the bore above the exhaust port involved.

[bigdawg10132009]

broken or frozen rings.....i am hoping just frozen on the 150......from what i have read, there is a plate on the side of the engine that can be removed (inspection plate i assume???) to view the pistons. but, does the piston drop below the plate enough to view the rings? sorry for all of the questions but i dont wanna mess things up. i am actually considering going to school to work on marine engines and such.....but for the time being, i will ask folks that know....the folks round here......much appreciated for the advice

[powerabout]

Bigdawg10132009

Yes the transfer port covers, one per cylinder on the outside of the block.
Remove the them and you will be looking at the side of the piston through the port windows and as you wind the flywheel around by had the piston will come down and go past the port.
If you stop it with the rings in the port and then get a firm blunt object with an end small enough to push on the rings they should press into the piston and spring back.
They should be cleanish on this side as it is the intake side.
If you want a better view you can remove the exhaust cover and plate from between the cylinders.
This being the hot side if there is a problem it will be there. You will also see how badly the carbon has built up.
The carbon build up is usually what sticks the ring and then overheats it especially the lower ring as its job is to transfer the heat out of the piston.
Try your engine cleaner to be sure its not stuck and if you are sure and it doesnt spring back it is probably broken.

Best of luck

[bigdawg10132009]

ok thanks.......i will give an update soon

[pistnbroke]

how many times has an old engine had the rings and bores done and then the crank fails ...like I said its an old engine if it runs ok then use it as it is

[bigdawg10132009]

again, thanks for all of the advice folks....

[Frosty]

big dawg thats ok you can go now, we will just hang around a bit and talk about you.

[pistnbroke]

We have put all this effort in so we would like to know how the engine compressions came up on re test

[tuantom]

What about the other two cylinders on that 150? It's a V6 - insn't it?
Throttle wide open during compression test?
Made that mistake on my Honda bike years ago - night and day results with the throttle closed or open.

[powerabout]

With the outboard you are just looking for the differnce to highlight a problem.

The captured volume is so small that gauge differences and especilly cranking speed effect the reading a lot.
Thats why the manuals hardly ever mention the pressure they would be too many arguments.

and yer what about the other 2 on the v6?

[bigdawg10132009]

ok folks......
after letting the cylinders soak in seafoam for a few days....i took readings of the cylinders again after i let the engine run for about five minutes at idle and slight rev....it smoked like a freight train to say the least!! HA!
the readings were as follows at wide open throttle, plugs on the leads and grounded......
left bank - 100, 100, 85
right bank - 100, 95, 100
there was carbon bits on the plugs when i removed them for the test. it seems to bog when i throttle it now (didnt before) and smokes like nobody's business. the smoke isnt all that blue....more whitish (head gasket????).....
but, i think i am gonna give the carbs a go through and run sea foam through again in the gas and via spray can......

[bigdawg10132009]

head gasket???? or maybe just burnin off the sea foam and extra oil i put in the gas....

[bigdawg10132009]

good news is that the 60 psi reading came up to 100 after the sea foam....

[pistnbroke]

I think its just the foam and the extra oil ..run these older motors at 50:1 ... you did well to get the comp up ..if you suspect seals on the crank between cylinders as being worn you can put seal expanding liquid in the oil and that will expand them 4 % ( I soaked an old lip seal in it at 21mm and after 3 weeks it was 19mm and supple ) great work ..now give every one who helped you some rep ..I see yours has gone from 10 to 13 so somebody loves you ...ha ha

[bigdawg10132009]

absolutely pistn!!! thanks EVERYBODY for all of the helpful advice.....i feel mo betta about spendin' the $350.00 for the boat, motor and trailer now....the motor is a VRO....do i need to change the VRO fuel pump out to a standard pump of just plug the oil line off and let her run....there looked like there was smoke coming from the fuel pump for some reason......

[pistnbroke]

VRO I assume you mean its oil injected ....so if you want to run on pre mix you just disconnet the pump and pipework and put 50 to 1 in the tank only .....if you do that and dont forget the oil ...Must be TWC 3 for outboards not chain saw oil the you can be sure its getting lubed

fuel pump and oil pump ..often electric in the tank are two diffeent things .the fuel pump works off crankcase pressure pulses ..no leccy required

[bigdawg10132009]

yepper....oil injected......
got some of the stuff specific to rudes.....

[Frosty]

For those not in USA, what is seafoam?

Brake fluid softens carbon deposits.

[bigdawg10132009]

seafoam is a liquid decarb agent (seafoam is the brand name) that can be put in the engine cylinders directly and/or in the gas and it also comes in spray form that can be sprayed into the carbs while the engine is running to help decarb rings, pistons, carbs etc.....

[powerabout]

I think its just the foam and the extra oil ..run these older motors at 50:1 ... you did well to get the comp up ..if you suspect seals on the crank between cylinders as being worn you can put seal expanding liquid in the oil and that will expand them 4 % ( I soaked an old lip seal in it at 21mm and after 3 weeks it was 19mm and supple ) great work ..now give every one who helped you some rep ..I see yours has gone from 10 to 13 so somebody loves you ...ha ha

pistnbroke
the seal rings between the cylinders are metal all US OMC / MERCS.
You need to have a built up crank to be able to put a seal on the crank which some jap stuff has.

only rubber seals are top and bottom of the crank.

[pistnbroke]

I think you misunderstand ...between each crankcase chamber there is a seal and if this leaks the transfer to the combustion chameber is affected ...yes/no

[Frosty]

Youve never had an outboard apart have you Piston?

There are no seals, not like you are thinking. They are called labyrinth seals.

They are close tolerance ridges that will allow air to pass but so slow and so poorly aerodynamically they seal one cylinder from another.

But you knew that didnt you?

Or as on OMC they are like huge piston rings that fit on the crank.

[powerabout]

yep wot he said

most small engines have labyrinth and larger seal rings so all omc V4, V6, V8 and merc V6
I'll bet the same with Yam but never played with them.

[pistnbroke]

sorry mate the ones I have had apart have had lip seals between each crank chamber .the last two cylinder susuki had 3 seals two outer and one in the center .....the crankshaft can be taken apart in sections to replace them which is a big pressing job which is why I suggested the seal expansion oil

hey you are a bit Frosty aint you ...ha ha .....stay cool but not frosty !!!!