Evinrude 70hp ideal compression?

[Henry McCullough]

I just bought a boat with an Evinrude 70 3cyl (1996) non vro . I picked it up pretty cheap because I was expecting to do some engine work. I started it up on the muffs and it seemed to by idling high (throttle tabs in carb were shut as far as they go) but running never the less. So I decided to take the boat for a test drive and the motor seemed to be running rough and would bog out when you have it some gas. So i took it home and did a compression check top-100 mid-90 bottom-100. So my question it is that what is causing the rough running? And what are the ideal psi for this motor.

 

[lmuss53]

Around 100 is not terrible for this motor if it sat for a while, it should run there. Mine has always tested at about 120 psi. Look at the throttle cable and make sure it is returning all the way back to where it touches the idle screw. I would get kits and rebuild these carbs next. BTW I'm almost certain that a '96 70 had to have VRO,so it has been removed.

Bogging down like it is running out of gas is a sign of several things. Is the gas fresh? Is the tank clean? Are the hose and primer bulb new and working right? If it sat for long, I would rebuild the fuel pump too,

 

[flyingscott]

How long did it sit. First run some mercury engine tune or similar through it when you get it running follow the instructions make sure you are running a 50-1 fuel mix. Then check the compression before you put a lot of money into it make sure that will be ok. You will probably need to go through the carbs/fuel system and replace the water pump.

 

[ondarvr]

You did the compresion test and the results were OK, but they don't mean much other than they are close enough. Don't run it if it's bogging, this frequently means it's running lean from gunk in the carbs, running lean can cause damage. Clean the carbs and see if it improves. A fuel pump doesn't typically cause an immediate reaction, it's normally delayed slightly.

 

[Henry McCullough]

Thanks for the replies. The carbs seem to be clean, i cleaned them out when i got it. The guy I got it from said it had been sitting for a little over a year. I should mention that it was running rough at idle, like idling up that dropping rpms abruptly? Almost as if i was hitting rocks while idling around, of course i was not hitting anything but similar behavior. And it wasn't bogging like it was running out of gas, i know that because these have the primer function (push in the key) and i tried to floor it then give it a few squirts with the primer and it only bogged down further. Leading me to believe its not gas related. So that low compression wouldn't cause this? i took off the head, and the cylinder walls seemed to have some scuffs, but no major chips or gouges. Any help is greatly appreciated!

 

[oldboat1]

possible lower unit issue (worn clutch dog), based on symptoms. Possible ignition miss.

 

[racerone]

????---some scuff in the cylinder walls.----No amount of fiddling / adjusting will fix that.---Motor has to come apart.

 

[lmuss53]

Just to be clear cleaning the carbs means removing them, disassembling them and soaking them in cleaner, cleaning the internal parts, cleaning out all the passages, setting the float height and reassembling. Sitting for as year especially with today's gas will gunk up the insides of any carb.

If it is still apart put up a few pics of the cylinder before you decide to tear it down completely.

 

[Henry McCullough]

Alright. I am aware of the carb cleaning process. I will put up pics when I pull the head. It looks like I am going to have to remove some of the cowlinmg to remove the cylinder? Also, when i pull the cylinder/cylinders, is there anything keeping the crank attached to the other case? other than the other case? thanks!

 

[racerone]

The powerhead must be removed from the exhaust housing in order for it to come apart.---When the crankcase cover is removed the crankshaft lays there attached to the rods.

 

[Henry McCullough]

Thank you for the replies. Ended up getting a Evinrude 70 parts motor with good compression. 130PSI in all three. It's just missing a few parts so im in the process of swaping out parts. Only trouble is getting the wiring harness to fit as the new motor is VRO and has a few more censors and the old one does not.

 

[flyingscott]

What year motor did you get not everything will interchange