'74 70hp burped and then died

[strap_76]

I have a 1974 70hp Evinrude model #70473M. I had it out twice this year. First time out it ran fine except for a brief second where it (burped) lost power then recovered. Second time out it was running fine then started to burp and then quit running completely. Couldnt even get it started after that.

Getting blue spark on all 3

Fuel from tank, bulb, quick disconnect good

Gas was stored with Sta-bil over the winter

Fuel filter clean

New impeller last year

Carbs rebuilt last year

What's the right way to check compression and fuel pump if that's what is causing this? Any help is greatly appreciated.......the fish aren't gonna catch themselves

 

[jonesg]

Re: '74 70hp burped and then died

Read the FAQ files.
http://forums.iboats.com/forumdisplay.php?f=31

Sounds like head gasket.

 

[strap_76]

Re: '74 70hp burped and then died

Thanks for your reply. I read the FAQ's and learned from it. I cant check comp now because it wont even start for a warm up. I pulled the carbs and dropped the L/U today. I noticed that my connection to the plastic fuel tank wasnt as tight as on the metal tank. I cant believe I didnt notice that before.

I also found an oily mixture in the L/U. It was inside the water pump too. Is that bad? If so what do I need to do to correct? Should I start a seperate question for that. I dont know. I really love this motor and want to take care of it. Everybody says its a "bulletproof motor." Im somewhat challenged mechanically but I want to learn and keep her running. Thanks in advance!

 

[jtexas]

Re: '74 70hp burped and then died

Go ahead with the compression test, cold motor, carbs off, l/u off...what you're looking for is the difference between cylinders. You can take proper compression readings later.

The "oily mixture"...you mean that's what came out when you drained the crankcase?

 

[strap_76]

Re: '74 70hp burped and then died

Thanks for the help,

Im a little worried about the comp test. I'm unclear about hooking up to the soleniod as in the FAQ.

As for the oily mixture, my heart goes out to the Gulf coast people. Mine is small in comparison. Ive got oil and water inside the water pump. I drained the L/U before all this. The impeller is fine and the pump seems normal. I noticed a rubber gasket at the top of the drive shaft and it needs replacing. I hope and dont hope that I am wasting your time. In a few days I will replace the worn out pieces and put it back together again. Hopefully, that works right. Like I said, its a great motor, and Ill probably be back for advice on maintenance. Thank you much!

PS what are the indications of a blown head gasket as per an earlier post?

 

[jtexas]

Re: '74 70hp burped and then died

The gearcase has two seals at the drive shaft, back-to-back; one keeps water out, the other keeps oil in. It's possible that one of the seals has failed. I'd think about pressure-testing the lower unit. Pump it up to about 12 PSI, see if holds for 5 or 8 minutes.

About the solenoid: for your compression test, you want to disable spark because you don't want to leave the spark plug leads open; one way to do that is to leave the key in the off position and jumper the solenoid. Another way is to pull the emergency lanyard (your motor wasn't factory-equipped with one, but a you or prior owner might've added one) and just use the key normally. Another choice would be to use jumper wires to ground the plug leads to the engine block.

Solenoid has two large terminals: the positive battery cable connects to one, and the other leads to the starter motor, and two small terminals: a black ground wire, and a red wire that provides 12V from the keyswitch. If you touch one end of a jumper wire to the battery cable terminal and the other to that small 12V terminal, it energizes the solenoid just as if you turned the key to start. Might spark just a little. Be careful not to connect that battery cable to the engine block, you'd get a huge shower of sparks.

If talkin bout boats is a waste of time, then I'm in big trouble........

 

[strap_76]

Re: '74 70hp burped and then died

Thanks for helping me. You said.........

Another choice would be to use jumper wires to ground the plug leads to the engine block.


.........this seems like the easiest way for a mechanically challenged fisherman like me. What should I use for jumper wires, just some copper wire or something? And do I just connect them to the metal of the spark plug wires and then to the engine block?

 

[jtexas]

Re: '74 70hp burped and then died

right, insulated copper wire, like 10- or 12-ga automotive wiring, connect to the plug boots and block, aligator clips or what have you.

 

[strap_76]

Re: '74 70hp burped and then died

Hey there,


I finally got the compression checked and I got 125 on #1, 75 on #2, and 130 on # 3. I have a Seloc manual and it says its probably bad piston rings. Im getting the camera out and preparing to pull the head. I gotta probably remove and replace alot more than just one thing. Temp switch, gaskets, rings........ect. I also have a question of reeds. I know this is totally layman but, I have the carbs off and was poking with a finger into the reeds. No. 2 on the left side seemed to be laying flat while the others had a slight give up and down. Is that bad? What is a guy to do?

Strap

 

[jtexas]

Re: '74 70hp burped and then died

it's bad to poke the reeds with your finger. Not sure what you mean by laying flat. If you were to take the intake manifold off and hold the reeds up to the light, you would want to not be able to see through 'em. No light coming through at all is ideal, but a sliver of light is ok. Reed inspection is a pretty simple operation.

When reeds are bad, the carb will spit up fuel.

Highly recommend you get a factory shop manual...seloc will let you down before you're finished.

You can test the thermostat in a pot of water on the stove with a kitchen thermometer, should open at around 123? F. The poppet valves, I'd just replace, they're cheap.

will be watching for the pics. good luck.

 

[strap_76]

Re: '74 70hp burped and then died

Hey there,

What I meant, with respect to reeds, is just sticking my finger in there and feeling the play of them. OK, Im digressing or getting ahead of myself. My bad. So far, I grounded the leads and did a comp test, like you said. Weak comp in #2. ONE question.........where do I get a REAL manual? Im about ready to pull the head off and do some checking around in there.....Seloc kinda sucks. Too much useless info and not enough. Ill try not to ask more questions till I get the real manual. Thanks THas.

Strap

 

[AlTn]

Re: '74 70hp burped and then died

outboardbooks.com...or ebay

 

[jtexas]

Re: '74 70hp burped and then died

or marineengine.com

Above I quoted 123? F as the 'stat temp, but it's more like 145?; the temp will be stamped on it. Sorry bout that.

The manual warns against manipulating the reeds with any foreign object (fingers included); I can't say from personal experience. Besides which, I wouldn't know how much "play" is acceptable anyway.

[p.s. don't toss the seloc...some of the photography is pretty good (gearcase especially), and a couple "special tool" workarounds. The starter motor rebuild write-up is pretty good, too.]

 

[strap_76]

Re: '74 70hp burped and then died

Ok thanks JTexas,

I checked out your website and I think I found the right book. Service Manual for Evinrude 1974 70hp #70473M. Sounds precise, thank you. It might take awhile, but Ill order ASAP. Then Ill get started step by step hopefully.

I appreciate you giving advice on thermosensor and reeds. I read in Seloc on how to test reeds with a note card. I think that is going to be tested after the head/cylinder issue is resolved. Sounds like the thermo is something that can be tested once I unbolt the head. Without the service manual.......what is the proper way to remove the thermo? Thats probably the first place for me to start. After that check the gasket and piston rings? Then again, I know nothing or where to start........hahaha.....but want to learn and do it right. Thanks

Strap

 

[jtexas]

Re: '74 70hp burped and then died

you can start with the thermostat.

remove these 5 bolts:

clean up the corrosion

(I used a powder called "Barkeep's Friend")

I believe your motor might have only the one poppet valve.
Can't pull the temp switch with the cylinder head in place.

Go ahead and replace the poppet valve grommets and springs

The plastic valve itself is pretty durable, if it's ok just reuse it.

 

[strap_76]

Re: '74 70hp burped and then died

Hey there,


I removed the cover, gasket, grommets, poppets, springs, thermostat sensor, and it's rubber seal. I cleaned most of the deposits up pretty good. I took some pics too but, the files are too big to upload here so I'm trying to figure that out for the future. Appreciate the help and pics especially. Its gonna take me a week or a little longer before I get the manual and replacement parts. Hope you are still there when I start getting deeper. Thanks for your time.

Strap

PS Once I get this step done, Whats next? Somebody told me I have a hole in my piston. Seloc says its piston rings. Just wondering.

 

[jtexas]

Re: '74 70hp burped and then died

PS Once I get this step done, Whats next? Somebody told me I have a hole in my piston. Seloc says its piston rings. Just wondering.

Just keep telling yourself, "it's just a blown head gasket."

No one can say, only a visual inspection will tell ya that. Pull the head, take some pics. You'll want to start a new thread, with something like "Help with rebuilding my motor" in the title, to get some of the more experienced old timers involved, that probably aren't following this thread.

The photo's I take with my phone are too big, too. I don't have a fancy photoshop application on my computer so I use a primitive process...insert it into an Excel spreadsheet, right-click and select "properties" from the pop-up menu, reduce the size, copy the reduced pic to Windows Paint and save it as .jpg I use Paint to add text, and to cut out part of a photo if I don't need the whole thing.

You can insert a larger photos into the body of your post: you have to upload it to a picture sharing website. I use www.photobucket.com it's free and works pretty good. Paste or type the URL of your uploaded photo into your post, preceded by IMG and followed by /IMG (IMG and /IMG both have to be in [brackets].

 

[strap_76]

Re: '74 70hp burped and then died

Its just a head gasket. I think I figured out the photo thing. Thanks again and Ill start a new thread soon.