1974 40hp Evinrude 40455s engine not reaching WOT

[buddhapi]

I purchased another 1974 40hp Evinrude motor that does not reach peak RPM's. it will idle so slow, you can count the number of flywheel teeth, and it starts on dime! I put in new spark plugs, and they're burning clean and dry. my thoughts are the power head is in excellent shape. I've readjusted the contact points, checked the fuel pump and filter. now, I'm cleaning the carburetor and not finding anything. is there any words of wisdom as far as maybe timing and carb control being "off", or is wide open just WOT?? it just seems boggy through the whole RPM range. not really any flat spots, just boggy. Max RPM is about 2 grand

 

[geoffwga1]

I purchased another 1974 40hp Evinrude motor that does not reach peak RPM's. it will idle so slow, you can count the number of flywheel teeth, and it starts on dime! I put in new spark plugs, and they're burning clean and dry. my thoughts are the power head is in excellent shape. I've readjusted the contact points, checked the fuel pump and filter. now, I'm cleaning the carburetor and not finding anything. is there any words of wisdom as far as maybe timing and carb control being "off", or is wide open just WOT?? it just seems boggy through the whole RPM range. not really any flat spots, just boggy. Max RPM is about 2 grand

At a guess I would say you are only running on one cylinder or the the carb is not as clean as you think it is.Do a drop test on the cylinders by pulling each lead off in turn while running (this can be exhilarating if you're not well insulated)If the motor stops when you pull one,it's the other that isn't working.

 

[buddhapi]

Thanks geoffga1. I had done that, and the RPMs fade on each cylinder. the Yamaha shop told the last owner that either the block was cracked or the reeds were messed up. As I say, this thing idles way to low to have 1 bad cylinder. it's running even for sure. I was wondering after my post last night....if my flywheel is turned in the center hub a few degrees, and throws the magnet position off......would it act like this?

 

[buddhapi]

when checking timing with a light, what RPMs would you check the marks at? Just in case my Clymer manual doesn't tell me.

 

[Bosunsmate]

theres a sticky file at top of all files which has one on timing.
You check max timing with plugs out, itl be 20 something
idle check rpm at what it idles comfortably at in a barrel,
If the flywheels turned the timing will be no where near the timing marks

 

[geoffwga1]

Thanks geoffga1. I had done that, and the RPMs fade on each cylinder. the Yamaha shop told the last owner that either the block was cracked or the reeds were messed up. As I say, this thing idles way to low to have 1 bad cylinder. it's running even for sure. I was wondering after my post last night....if my flywheel is turned in the center hub a few degrees, and throws the magnet position off......would it act like this?

If your flywheel had moved it would have sheared the key and it's unlikely it would start,let alone idle.Only way to check is to remove the flywheel and take a look..If you have to replace the key be sure and get it from a proper OMC dealer,do not use the hardware shop variety..If you're sure about the ignition I would turn my attention back to fuel issues or air leaks. when you have it running Open it up a bit and when it is at it's maximum sqeeze the fuel bulb a few times, I would try bypassing the filter too..Then check that the main jet cork washer in the float bowl is okay and that you didn't inadvertently leave it out when you stripped the carb.You did strip it didn't you,just a cleanup without a good soaking and blowing out is often a waste of time as it doesn't clean allthe little orifices.Just occured to me,are you ruuning it in a tank.if so you probably aren't putting irt in gear and revving it.I hope not anyway 'cos it would probably take off across the yard.The point I am making (rather lengthily,sorry) is that you can't open ity right up unless it is ingerar so you won't know what it;ll do till you take it to open water and try it.
Let us know what happens.

 

[buddhapi]

hey, geoffwga1. I'm wondering if the inner hub would have spun a bit from the outer wheel part? hub looks like steel, but the main flywheel looks aluminum. I had it out on the lake Saturday and it runs just as doggy as it did and does now in the barrel. I see no timing marks at all on the flywheel...top or side. the fuel bulb stays hard pretty continuous, so my pump is good. I didn't get the carb back together yet,but I will tomorrow. the main jet cork washer was in place, but it does seem a bit used up. I never have fuel coming out of the front of carb, so it's not flooding over...? Or, is the extra fuel just getting pumped out the exhaust? I will look at the washer better tomorrow. thanks for the heads-up

 

[racerone]

Actually there are timing marks on the flywheel.----Just start the motor and point your timing light at the 2 vertical lines on the magneto plate.-----A timing mark should be visible on the flywheel and it fires between those 2 vertical lines.

 

[buddhapi]

Well, I made it back. new contact points and capacitors. new NGK plugs, checked the flywheel hub again and it definitely hasn't slipped. compression is even at 110 each. I'll explain. this motor runs like a snowmobile engine that is loaded with unburned gas and oil in the crankcase. in that case, I would pull the drain plugs from the bottom of motor to relieve. wouldn't these outboard motors just automatically do this with gravity....right out the exhaust port holes???
Next, I see in the exhaust housing diagram a # 63 which is an exhaust housing cover, held on by #62, which is a single screw. what is the purpose of this? can I see it if I pull the lower unit off again? I have a 5 inch extension on my motor. could this be plugged? too much back pressure? 14oz oil to 6 gallons of gas.

 

[F_R]

Nice thinking, but you are letting your imagination run wild now. But you are correct on one point, it will clear itself out if the flooding cause is removed. So why is it flooding? I don't know. Either it is dumping too much gas in or it isn't burning it. I would guess the first.

The plate in the exhaust is not doing it. That is there as part of the relief system that blows exhaust (and water) out the blow hole in back. If it were missing, it would just be noisy. And no way in hades is the 5" extension plugged unless a possum crawled up in there and died.

 

[steelespike]

Excess fuel in the crankcase used to just dump into the water. I think your motor may recirculate it into the intake.
This some times makes a rough idle. Maybe your super smooth idle indicates the crankcase drain is plugged.?
If you had slightly bad head gasket or a crack in the power head a mall amount of water may be getting in the combustion chamber.
Just enough to slow things.Sometimes a plug that stays shiny clean indicates water infiltration.
Also the piston head may be clean.

 

[buddhapi]

Thanks for the replies. I did word it wrong. I'm wondering if that exhaust cover could be plugged and giving me an issue, but maybe I can't see that with the 5" extension hanging below it. I've had the carb apart and it's super clean, with a new washer on the high speed jet tube...no adjustment needle on that either. no signs of water. no droplets and no white electrodes. the plugs are dark and the top one seems a little moist. not really flooded wet, but not completely dry. I've sprayed around the entire motor with carb spray to find an air leak and found nothing. I'll pull those little fuel lines off the crankcase and check for obstruction. maybe full of carbon deposit?

 

[buddhapi]

so I'm playing with it again this morning, and I see that the two drain hoses from the cylinders are going back to the bottom of the intake manifold...after the reed's, which makes zero sense to my own auto mechanics' mind. the two hoses connect to what is called a recirculating valve. my 35hp Evinrude doesn't have that. the top hose weeped over a teaspoon of fuel when I pulled it off the valve, but the lower hose had a couple dribbles. does anybody know what is all part of this Recirculating valve?

 

[racerone]

The fuel may go from the drain valve to the the cylinder and not from the cylinder to the drain valve.

 

[buddhapi]

I think you are correct, racerone. I wonder if anyone on here can explain this to me. the amount of fuel squirting from these hoses TO the cylinders is almost enough to run this motor on...I almost want to say this is why my motor is loading up....Or am I missing something major? I have a manual, but it doesn't talk about this in length. I see Evinrude ran this recirculating valve on the 1971-1976 and the 1983-1986 40hp motors. was this their early quick fix to get rid of those beautiful rainbow stripes in the water? why would you want to push more raw fuel into the cylinders of an already dialed and tuned motor???

 

[Bosunsmate]

something major i suspect.
if you have pulled the line and its squirting fuel it shouldnt be as it works by sucking from vacuum at the cylinder so the moment you detach that there there shouldnt be any power to push the fuel through.
Unless your crankcase is full of fuel, the only reason for that would be if your choke is stuck open
In normal practice i think it also helps with starting as on a 90 that had them that was hard to start i cleared this line and it was then fine

 

[buddhapi]

hmmmm. I pulled both hoses off the cylinder covers while it was running, and the fuel was squirting out of the hoses, from the valve in front of the motor. the RPM's didn't seem to change though. I'm thinking that would have caused 2 small vacuum leaks....or maybe the holes are too tiny to make that much difference. I will some how try to get all the fuel out of the crankcase. it was definitely squirting out of the hoses without vacuum pulling it. that would mean the crank case is full of unburnt fuel???

 

[Bosunsmate]

im not sure, maybe crankcase compression could make it squirt too,
Is your choke solenoid shutting off properly?
I would think a squirt would quickly flood a engine cylinder, as its not atomised with air like the fuel is in the carb too

 

[buddhapi]

I actually don't have the electric choke hooked up yet, as the toggle switch is up in the dash for that, and I have the harness hanging over the rear of the boat so I make less steps to keep starting it. I choke it manually to start and then push the choke in. would it hurt anything if I cap off those two cover port nipples, and run the two hoses into an overflow jar of some sort. maybe that would clean it out? then I would try to hook them back up again when cured.

 

[racerone]

Fuel is pumped from the crankcase to the cylinder via that wee hose !!!!!!-----That is just the way it works.----You might want to check the fuel pump diaphragm.----