1970 4 hp Evinrude stops suddenly

[twocyclemania]

Picked up a 1970 4 hp. The motor runs great and then after a few minutes it just dies out suddenly. The exhaust/water mix on the leg seemed a bit hot (on the hand) so I replaced the impeller (which was shot). The pump body appears to be passable. Started it back up and now the leg exhaust/water mix is 'comfortable to the hand' but it still stops for no apparent reason as it did before. It's not like it's seizing; it just stops. I did note that the head is hot and when I sprinkle water on it it sizzles. I understand that the head on those small motors my be hot. The motor itself has very minor corrosion. Is it stopping because it's overheating and should I pull the head. The head gasket is not blown as far as water in the cylinders.

 

[F_R]

Fuel pump??
You sat it is not hot nor seizing, otherwise I'd suggest a possible hole worn through the side of the water tube. It wouldn't be the first one.

 

[racerone]

Water sizzling on the head means it is too hot.-----Have you had the flywheel off to inspect the ignition coils ?-----Compression test done ?----A blown head gasket is one possible cause of overheating.

 

[Crosbyman]

why not clean the carb inspec the coils for cracks

test the ohms value bettwen plug boots and engine body you should see 4-8 kohms steady could be plug wires flexing and open

these engines are not very complicated but require the usual TLC
carb impeller coils plugs timing ajustments etc...

Maintaining Johnson/Evinrude 4h

 

[twocyclemania]

Since the head appears to be too hot I thought I'd open it up and make sure the water chambers are not clogged and replace the head gasket. I went to loosen the head bolts and found they were far from being torqued down. In fact they were not much more than finger tight (blown head gasket? as suggested). No water in the cylinders though.
Will pull the flywheel and check the coils; sounds like a good idea as I know coils can act up after running for a bit if they're bad. And will do the compression. Will get back to you on that.
Going to order the head gasket and also exhaust cover gasket. Thanks everybody for your helpl

 

[twocyclemania]

Since the head appears to be too hot I thought I'd open it up and make sure the water chambers are not clogged and replace the head gasket. I went to loosen the head bolts and found they were far from being torqued down. In fact they were not much more than finger tight (blown head gasket? as suggested). No water in the cylinders though.
Will pull the flywheel and check the coils; sounds like a good idea as I know coils can act up after running for a bit if they're bad. And will do the compression. Will get back to you on that.
Going to order the head gasket and also exhaust cover gasket. Thanks everybody for your helpl

Replaced the head gasket. Water chambers were very clean. Did a compression test after. 70 exactly on both cylinders. Ran the motor and the exhaust/spray coming out the leg holes was comfortable to the hand. However, the head still 'sizzles' water and the motor started to stall. It was due to the overheating as it was about to seize. Shut it down and spun the flywheel and I could tell overheating is the problem. (compression test after that). I do have a new impeller, pump grommet and the pump body looks okay. Only thing I can figure is that either (as was suggested) there's a hole in the water pipe or the grommet at the top of the pipe is bad. I'm going to have to pull the power head. Other than that, I'm open to suggestions. BTW: It runs great until overheating after a few minutes.

 

[Crosbyman]

sounds like an internal clog... bad coils could fail as well as broken wires but I can't see them causing overheating

with the head off see if you can probe, wiggle a nylon line (weed wacker stuff) up and in accessible water ways .
try strong air pressure backwards etc...


btw I hope you are not bucket testing this kicker because air bubbles generated at high speeds in a bucket will reduce water intake and heat up the engine... always lake test for high speeds !

 

[Crosbyman]

see picture clean out the lower exit route check bypass exit back flush it


install the head gasket and cyl head back flush from cyl jacket exit water should flow back out the entry point

 

[twocyclemania]

Yes I am running it in a barrel. Now I'm going to run it on a lake before I do anything else. Thanks for the heads-up. Do you think running it without the prop and at a medium or low speed (would not run it high w/out the prop) in the barrel would give me an indication if I'm okay or not? Thanks Crosbyman!
ps I also have a 59 3 hp that does run hot (after all the replacements) and I put it in the back of the shed for another day.

 

[Crosbyman]

with no prop chances are it will cool OK


it will be much better than churning up fizz water for the pump

 

[twocyclemania]

Thanks to everyone for their replies and suggestions! Solved some of the problem but not all. Did a new head gasket, compression test (70 both cylinders). Discovered both ends of the hose from the fuel pump to the carb were leaking. Probably why it shuts down suddenly; after the initial bulb squeeze fuel is gone. As for the overheating; ran it with the prop off (in barrel) and it's still overheating. The head is hot (sizzles water). Was going to use the infrared thermometer on the block as suggested but splashed some water on the block and that also sizzled. Gotta be well above the suggested 165 degrees. Odd thing is that the exhaust/spray mix coming out the leg holes is not very hot. It's very comfortable to the touch. Popped the flywheel and the coils look great and dressed the points. The motor does have good spark. With all the suggestions and what I've eliminated I think I"m going to have to pull the powerhead and check out the water tube and top grommet. Any other ideas and I'll check them out. Once again, everybody 'thanks'

 

[Crosbyman]

see if you can blow out the water passages... possibly an old rubber piece stuck inside

with the power head off try to fish a mono line from a weed wacker in the available opennings incl the watre tube

 

[oldboat1]

Thanks to everyone for their replies and suggestions! Solved some of the problem but not all. Did a new head gasket, compression test (70 both cylinders). Discovered both ends of the hose from the fuel pump to the carb were leaking. Probably why it shuts down suddenly; after the initial bulb squeeze fuel is gone. As for the overheating; ran it with the prop off (in barrel) and it's still overheating. The head is hot (sizzles water). Was going to use the infrared thermometer on the block as suggested but splashed some water on the block and that also sizzled. Gotta be well above the suggested 165 degrees. Odd thing is that the exhaust/spray mix coming out the leg holes is not very hot. It's very comfortable to the touch. Popped the flywheel and the coils look great and dressed the points. The motor does have good spark. With all the suggestions and what I've eliminated I think I"m going to have to pull the powerhead and check out the water tube and top grommet. Any other ideas and I'll check them out. Once again, everybody 'thanks'

160F is overheating. Motor should run/idle at about 120 or 130F -- maybe 140 if the water in the barrel warms up enough. The cooling water must be 6 to 8 inches above the pump. Run the water to about half way up the shaft just to make sure.

 

[Crosbyman]

see if you can blow out the water passages... possibly an old rubber piece stuck inside

with the power head off try to fish a mono line from a weed wacker in the available opennings incl the watre tube

if the impeller /water tube section is ok .try REVERSE air blow out starting at the water EXIT points

I have never tried it myself but you may be able to fish a mono line all the way across the water entry to the exit points shown the picture above or possibly vice versa .

check the base gasket for obstruction on the exit route .. yet with plenty of lukewarm water out the small lower holes some water is circulating so the pump/tube must be ok. the cyl jacket portion is getting hot so recheck/focus on the water supply hole above the top cyl and exit at the bottom

you can always try to circulate windshield washer fluid* in the water channels to see how good or not it actually flows out the discharge paths
*(to prevent any internal rust should it spill into internal cavities and cylinders )

 

[racerone]

A factory new impeller or perhaps one of the " chinesium " variety ?

 

[twocyclemania]

A factory new impeller or perhaps one of the " chinesium " variety ?

No: A real OMC. I used one of the chine ones once and never again.

 

[tphoyt]

I’m sorry but it drives me crazy when people bash Chinese quality. The ones to blame are the companies that spec their products to be made. If you spec a quality product that’s what you will get but it comes at a higher price and that’s when things go down hill.
I have spent some time in China and have found that products made in China for China are top quality products.
Again my apologies for the of topic rant.

 

[racerone]

The company / shop where i used to work makes precision parts.------Can hold tolerances of +- 0.000020"( 20 millionths )-----They now gets drawings in with an extra note.------Says " no materials sourced from China allowed in the manufacture of the product "

 

[Crosbyman]

I’m sorry but it drives me crazy when people bash Chinese quality. The ones to blame are the companies that spec their products to be made. If you spec a quality product that’s what you will get but it comes at a higher price and that’s when things go down hill.
I have spent some time in China and have found that products made in China for China are top quality products.
Again my apologies for the of topic rant.

depends... my son use to ha ve bicyles made in China for import and quality was so bad the import company he worked for folded due to to may returns due to broken pîeces. The big retail store had an iron clad contract and did not eat the losses the import company did.

returns. exceeded 25%
so it depends on a lot of things .. bad specs... bad manufacturing cheap metals etc...

 

[clemsonfor]

Water sizzling on the head means it is too hot.-----Have you had the flywheel off to inspect the ignition coils ?-----Compression test done ?----A blown head gasket is one possible cause of overheating.

Yep I was going to say the same thing. You should be able to touch the head while running for a few seconds and not say it's hot or have to pull your hand away.