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4hp problems Losing revs amp overheating

T

tomf

Regular Contributor
"Hi all,

working on a 1980

"Hi all,

working on a 1980 Evinrude 4hp (E4BRCSS) that has me a bit stumped at the moment. Not sure if these two problems are separate or interconnected:

1. I can usually get the motor to start and run at WOT but if I bring down the throttle, it loses revs and dies. However, I can usually keep it running indefinitely if I ride the choke manually each time it starts to crap out. Starting usually involves numerous pulls of the cord and all kinds of manipulation of the choke and throttle settings.

2. The motor also seems to be overheating - within moments of starting up, the exhaust cover plate gets boiling hot (literally!). However, cooling water would appear to be circulating (see below).

The motor has an integral fuel tank and a carb with the single needle valve for the slow speed mix. I don't know the history of the unit, but supposedly it's been sitting in the previous owner's garage for years.

Work done so far:

- Full carb clean and rebuild even before I started it up for the first time
- Cleaned fuel tank valve and replaced fuel line+filter
- Cylinder decarb with PowerTune spray
- Replaced & gapped plugs
- Carb needle valve backed out about 1.5 turns from seat, however before I can get it to run better I haven't even gotten to the point where I can think of fine-tuning this adjustment...
- Replaced water pump impeller
- Tested water circulation with a hose into the tube, and it comes out from the exhaust holes as expected.
- Water tube is definitely inserted correctly in the pump housing.
- Also, droplets of spray are apparent from the exhaust when pulling the starter cord.

Not quite sure where I should be looking next... Any hints appreciated!"
 
"Check fuel flow from tank to

"Check fuel flow from tank to carb.

(Carburetor Adjustments - Two Adjustable N/Vs)
(J. Reeves)

Initial settings are: Bottom high speed = seat gently, then open 1 turn out. Top slow speed = seat gently, then open 1-1/2 turns.

Setting the high and low needle valves properly:

NOTE: For engines that DO NOT have a shift selection, obviously there is no NEUTRAL position. Simply lower the rpms to the lowest setting to obtain the low speed needle valve adjustment.

(High Speed) Start engine (it will run pretty rough), shift into forward gear, take up to full throttle. In segments of 1/8 turn, waiting for the engine to respond between turns, start turning in the bottom high speed needle valve. You'll reach a point whereas the engine will either start to die out or spit back (sounds like a mild backfire). At that point, back out the needle valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest setting.

(Low Speed) Slow the engine down to where it just stays running. Shift into neutral. Again in segments of 1/8 turns, start to turn the top needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running. Eventually you'll hit the point where the engine wants to die out or it will spit back. Again, at that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustments, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay store at:

http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store"
 
"Thanks, I'll have to doub

"Thanks, I'll have to double-check for any blockages.

As for the overheating, is this something that could happen simply because the motor isn't getting enough fuel?"
 
No the overheating is a sepera

No the overheating is a seperate issue...try turning the low speed adjustment out another turn and see if things improve and let us know
 
"As for 'overheat':
T

"As for 'overheat':
The exhaust cover on that engine is only water cooled at one edge, and gets burning hot!
As for idle problem:
The idle circuit in the carb does not work properly. Either you have a blockage in the fuel channel or an air-leak."
 
"OK, thanks guys. I knew the c

"OK, thanks guys. I knew the cover would get hot, but didn't expect that being able to boil water on it would be normal.
happy.gif
Guess I'll tick that off my list of things to worry about then...

Re: the main issue, the idling, I'm sort of leaning towards the air leak explanation, since I'm pretty sure the fuel line is clear -- the fact that I can keep it running at low revs by slightly closing the choke would suggest a drastically lean mixture to me. And it does run full out so it must be getting fuel, right? I did try turning the valve out more, but it didn't seem to make a difference.

Any ideas where an air leak could be, or how to test for it? The intake manifold gasket is brand new, and AFAICT the carb is screwed on tight. The needle valve nut is also snug with new packing.

I guess another possibility is that one of the small passages in the carb is still gunked up, so maybe I'll try another soaking in carb cleaner and a blow-out with compressed air."
 
"If not mistaken, do not have

"If not mistaken, do not have a carb to 'check' at hand, the center 'main jet tube' even supplies fuel to the idle channel on top. If that tube does not seal properly in the top, you will have an air leak."
 
"OK, cool - I'll check tha

"OK, cool - I'll check that as well the next time I get to the motor."
 
i have a sea king 1961
model

i have a sea king 1961
model GG18736 ser.16x811906 having problems
with getting hot. the water pump is bad i like
to find one but having problems finding one. can anybody help me thanks
}}}}
 
"Really scratching my head her

"Really scratching my head here. Fuel delivery to carb is positively confirmed. Took it apart again and blew compressed air through all the passages I could find for about the third time. As far as I can see, the "main tube" across the carb throat is in place solidly, and the carb is seated tight on the manifold. Adjustment valve is packed snugly.

Still no difference - the mixture seems to be grossly out of whack. The weird thing is that the engine runs ok at all revs and even idles reasonably well if I keep my thumb in front of the carb air intake. (Talk about "manual choke"!)
lol.gif


Starting of thinking I should just try to find another carb somewhere, or sell the darn thing for parts... seems like a shame since with the exception of this problem the engine is in remarkably clean condition for its age. Sigh. Further ideas, anyone?"
 
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