1976 135hp V4 - compression test done

[waterbabies81]

Looking from the rear at the motor....

top left - 130psi
bottom left 140psi
top right - 148psi
bottom right - 148psi

Not sure where to go from here with the diagnosis guys.
I'm going to tear off the carb tomorrow and give'r a good cleaning, any other suggestions.

ps. wife found a website that had the manuals in zip for the 1973 - 1989 v4 motors. 48 - 235hp
if anyone needs a copy of the manual just let me know.

 

[kmarine]

Re: 1976 135hp V4 - compression test done

Looks like good compression for an old motor. Clean carbs are a must. you are on the right track. Pour some fuel into a plastic container and see if you have clean fuel in your tank before pumping old dirty fuel into your cleaned carbs or you may have the same problemb again.

 

[waterbabies81]

Re: 1976 135hp V4 - compression test done

Looks like good compression for an old motor. Clean carbs are a must. you are on the right track. Pour some fuel into a plastic container and see if you have clean fuel in your tank before pumping old dirty fuel into your cleaned carbs or you may have the same problemb again.

how do I get fuel from my boat under the floor into a tank which I can see... I added abit of fuel stabil and some 2stroke oil to it before which also makes me wonder... is this motor oil inj. or needs to run on mixed gas? cause I couldn't see a resevoir for any oil near the motor.

 

[waterbabies81]

Re: 1976 135hp V4 - compression test done



is this the manual I need cause for some reason it doesn't have larger motors pre 85

 

[kmarine]

Re: 1976 135hp V4 - compression test done

I use a primer bulb for the outboard motor. you can get a seprate dis connedct fuel fiting or remove the one from the fuel line. I doubt the 1976 engine is oil injected. Unless you have a seprate oil tank and oil lines going to your engine you have to mix the fuel.

 

[emdsapmgr]

Re: 1976 135hp V4 - compression test done

Don't waste your money on these manuals. Get an original factory manual from this website: outboardbooks.com. That's the only way to go. Your compression is unusual, not normal. It's pretty high. It is normal for the compression to vary from one head to the other, based on how the block was originally machined from the factory. It's normal to see maybe 5-6 lbs variance between heads. You may want to use another compression gauge to verify your numbers. I'd probably shine a pencil light in the spark plug hole on the 130 cylinder and visually inspect the piston crown and the cyl walls to make sure it compares to the other 3 cylinders. That year engine did not have the VRO system-as stated you have to premix oil in the fuel at a 50:1 ratio.

 

[Fleetwin]

Re: 1976 135hp V4 - compression test done

You're on the ragged edge of acceptable variation between cylinders.

If you didn't know about the 50:1 mixture of gas to oil, you may have cooked that cylinder.

I would not run it anymore on the built in tank. Get a six gallon tank that you know what's in it. Mix 6 gallons of unleaded, 87 octane, to one pint of TCW-3 outboard oil.

Run it on known good gas/oil and see what happens. If it runs better, I would do this: http://forums.iboats.com/showthread.php?p=2648076#post2648076

 

[waterbabies81]

Re: 1976 135hp V4 - compression test done

ok well I'm going to pull the carbs and do a cleaning on em and then I'll check the fuel and see if I cant get that straightened out.

is there any way to test the mixture of the fuel in my onboard tank?
I'm guessing just siphon it out and make a proper mixture instead and toss the old fuel on a bonfire lol.

 

[waterbabies81]

Re: 1976 135hp V4 - compression test done

one other thing... the plugs:
the 2 plugs from the high compression cylinders were oily
the 130psi one was quite dry and the other was a split between the dry and oily one.

 

[Fleetwin]

Re: 1976 135hp V4 - compression test done

is there any way to test the mixture of the fuel in my onboard tank?
I'm guessing just siphon it out and make a proper mixture instead and toss the old fuel on a bonfire lol.

Not that I know of.

 

[Fleetwin]

Re: 1976 135hp V4 - compression test done

one other thing... the plugs:
the 2 plugs from the high compression cylinders were oily
the 130psi one was quite dry and the other was a split between the dry and oily one.

There is a good clue. The dry plug cylinder is starving for fuel.

 

[emdsapmgr]

Re: 1976 135hp V4 - compression test done

Agree. I'd pull the carb that feeds the 130 lb cylinder. Once apart, visually check the jets in that side of the carb that feeds the 130 cylinder. You'll have to pull them out- a special screwdriver will be required. Possible the main is plugged with some restriction. That engine may have original fuel hoses. If so, they are not able to handle today's ethanol fuels. Possible that some of the hoses are degrading and bits/pcs of hose may be travelling through the fuel system and could lodge in the jets.

 

[waterbabies81]

Re: 1976 135hp V4 - compression test done

how many jets are supposed to be in the bottom of the float bowl... I have a 58c that was seated fully and then a 61c on top of it and then a 61c on the other side and nothing else. and there was a piece of gasket material in one of the those jets. I believe it was in the one that only had the single 61c jet. rest of the carb seemed fine and the fuel lines were replaced at some point.

I'm going to pull the bottom carb off now and see what I find.

 

[emdsapmgr]

Re: 1976 135hp V4 - compression test done

The .058 jet is incorrect. You should have two jets, one on each side of the float bowl, behind the drain screws. Both main jets should be .061. If you also have a .058 jet on top of the .061, likely it has been running lean. In addition, likely the paper may have been blocking fuel flow and may have contributed to cylinder wear and possibly that low compression reading. If that 130 cyl was run dry, that could partly explain the low reading. Clean, reassemble the carbs, then put fuel in them and retest your compression. The normal flow of fuel/oil from the carb may help (lubricate) to bring the compression up somewhat on that low cyl.

 

[waterbabies81]

Re: 1976 135hp V4 - compression test done

ok so I've cleaned both carbs out except there are those caps that are punched in. I didn't deal with those or whatever is beneath them.
sprayed carb cleaner through everything, reassembled and will finish that another day.

all jets behind the drain plugs are 61c and are fully seated.
I pulled the brass screws on the side of the carb and the jets behind those and they are now fully seated.

I put some of the fuel from the main tank into my measurement bottle and it's a bluey green color in mass quantities and about the same color when pouring I use in a skil chop saw at work which is 50:1 as well.

so hopefully I'll be able to get it running and in the water this weekend.
Unfortunately my 3yr old daughter put a stop to work toady as she was in the hospital all morning with her first asthma attack. So she wanted to come home to recover. Just cant say no to that girl lol.

anyways thanks for the help I'll keep you all posted.

 

[emdsapmgr]

Re: 1976 135hp V4 - compression test done

I've never had a carb that was so filled with debris that I had to remove the core plugs inside the carbs. Usually a good spraying/cleaning with a Gumout type product does the job.