1977 70HP Evinrude will not go

[sleddogs13]

Bogged down late last year to 2 or 3 miles per hour. We had used the boat a few months and it ran good. Replaced power pack, coils, rebuilt carbs. Did not find high speed jet.The carb diagram on the shop.evinrude parts website does not note a high speed jet just a slow speed one. Found the low speed jet. It appears this carb just has two screws in the front one high on the carb and one on the bottom bowl in the front of the carb. They do not adjust just screw in.

Started right up. Went to give it a little throttle and it would just bog down and die. Spark plugs are wet. Idles up fine. Cannnot pull wires to check for engine change because it never or rarely get up to high speed. Only a few times it took off at half speed. Then it bogs down big time! How can we check for spark. The power pack is aftermarket CDI and Coils to. Fuel tank lines are all new and carb hoses to. Bulb on fuel tank is hard when engine runs and gas is new. After spending all this time and money it runs just like the end of last year if not a little worse. Any help would be great!

 

[jtexas]

Re: 1977 70HP Evinrude will not go

The high speed jet is behind that screw at the bottom of the carb bowl. You're correct that the jets are fixed, no adjustment necessary.

Did you link & sync after the carb rebuild?

Hope you kept the powerpack and coils you took off there last year -- it's nice to have spare parts on hand.

 

[Homedad]

Re: 1977 70HP Evinrude will not go

Are you sure you hooked your coils up to the correct terminals of the power pack. I just bought a motor that was doing the same thing and come to find out the previous owner had the wires hooked up incorrectly. The jets are fixed and for the most part don't need replaced. When you rebuilt the carbs did you check the link and sync to ensure the carbs are set as they should be. You can check spark with a spark tester from the coils or you can pull a plug and put it into the plug wire and ground it to the powerhead.

 

[sleddogs13]

Re: 1977 70HP Evinrude will not go

Did not do a link and sync. I will get a manual tommorrow and follow the timing intructions and so forth.

Also changed the plugs last night. Went on the lake this morning to try it. Starts right up smooth. Went to give it some throttle bogged down right away.

Went aroung in a circle near the dock very unhappy. But there she goes 30mph. Thought problem was solved had my dog riding shotgun around the whole lake. Backed it down idled her down. Went quickly to full throttle off she went. -- Happiness however it did appear just a tad slower than last summer. Was getting ready to bring her in easy. Decided to test the throttle one more time bogged down big time. Took cover off motor nothing evident. Wire in place. Shut it off started right up putted back in unhappy camper. Ready to buy the manual for the link and sync exercise Thanks guys

 

[djeady]

Re: 1977 70HP Evinrude will not go

I've been haing similar problems with a slightly older Evinrude 70. So far, I've found the following:

- spark plug lead on lower cylinder may have been shorting out to cover latch - repositioned lead
- one wire in wiring harness had insulation worn off, this was causing the motor to pop the main fuse
- a lot of crap in my fuel - I have a large canister filter and have emptied crap out of this twice now

Not completely resolved, but getting better - keep plugging away - and don't forget it may be multiple problems interacting.

 

[jtexas]

Re: 1977 70HP Evinrude will not go

generally fully blown link & sync isn't required when all you've done is pull the carbs for rebuild, usually it all goes back on pretty much like it came off.

If it dies when you put the hammer down, but you can nurse it up to WOT, couple things I know of cause that: idle speed set too low, and the roller (middle carb linkage) hitting the cam too soon -- the timing advance has to start before the carb throttles start to open. There's a mark embossed on the cam, the roller should hit that mark. Idle speed should be 750-800 in gear in the water so set it at 950or so on the muffs, then fine-tune it at the lake.

Make sure the carb throttle valves are parallel, closed at idle, horizontal (not beyond) at WOT, and the choke plates stay open except when you engage the choke.

Link & sync issues aren't usually intermittent, either works or it don't. I had a plastic bushing break off the throttle-timing advance rod once, made for squirrely symptoms like that.

Bad fuel can do it, too.

 

[sleddogs13]

Re: 1977 70HP Evinrude will not go

I did meddle with the rod with the timing mark I turned it in and turned it
out a few times last year in an attempt to increase and lower my idle speed.

I have the manual it looks easy to do the link & sinc just a few steps.

I also bought an OMC fuel pump repair kit for this motor. The manual states the pump is not servicable beyound cleaning the screen. Just by a new fuel pump for $95. I did sqeeze the gas tank bulb when it had trouble and it was hard. The choke casued the motor to stall.

Can't wait to have the motor purring. It am hoping for the link & sinc!

 

[jtexas]

Re: 1977 70HP Evinrude will not go

yeah the manual says that about the pump, but the sierra kit I bought on iboats fit just right.

if pumping the primer bulb while its acting up makes it run better, that might indicate weak fuel pump; that pump, if the diaphram gets perforated, gas dribbles out the hole on the back of the housing.

 

[sleddogs13]

Re: 1977 70HP Evinrude will not go

I tried to do the linc & sinc. Did not know how many RPM's it was going the book states to set the spark advance at 4500 rpm's. How do we know?

Also the I looked in the carborators and the flaps only were 3/4 hoizontal at wide open throttle. We had to manually push the lever on the motor near the cam mark to open them up all the way.

 

[jtexas]

Re: 1977 70HP Evinrude will not go

Adjust the WOT stop screw, until the throttles open up all the way.

What book are you using, that tells you to use RPMs for the spark advance setting?

you should be setting your max spark advance with a timing light, with the engine running in a tank with a test wheel, or else using the procedure described here:
http://forums.iboats.com/showthread.php?t=228183

RPMs are measured with a "tachometer" -- if you only have one gauge on the boat, that's the one to have, it's an important diagnostic tool.

btw, by revving your engine beyond 1500 or so while the lower unit is not submerged, you risk "thermal runaway" (aka "preignition runaway"), in which carbon build-up in the cylinders heats up enough to ignite the incoming air/fuel charge; with the engine completely unloaded this is the equivalent of a spark advance way beyond where it ever should be. RPMs can race up out of control beyond design tolerances; the spark plugs become irrelevant, so the key won't shut the motor off. Choking the motor in hopes of flooding it out is the only hope.

 

[sleddogs13]

Re: 1977 70HP Evinrude will not go

Sarted in the driveway with the muffs. Just touched the key and she started right up. Had some trouble with the shifter and cable though. Stuck and jammed had to take apart and reasemble. Thinking I should replace the shifter control and cables.

Went to lake ready for fishing. Best I could get was a sputter for two hours. Working away never left dock.

First time ever would not start.

Went home parked in driveway downhill. Tested her started right up smooth!

Clean gas vented gas can. Incredible. Ran without engine cover on at the lake and in the driveway. fuel pump? Ready to buy a new motor. Anybosy know a good shifter cable kit -- in case it runs on the lake

 

[sleddogs13]

Re: 1977 70HP Evinrude will not go

Went to Maine after replacing the fuel pump and checking the timing at about 2500 rpm. The motor bogged down with white caps on Rangely lake and we limped back after running about 3 minutes.
All vacation played with stopping the bogging down even went to a marine mechanic who took it out of course it did not bog down then. A quick $85 bill. Went back to the camp. It would not start. Kept turning her over until she fired up. Put K-1 gas additive in tank to relieve the water problem in the new gas. A couple of other guys with boats had workrd on their boats for days to.

Could not go tubing could not go far. Even got it going raced around for about 30 minutes with me checking the timing hanging over the back of the boat looked like 19 degrees. Bought her back in to the camp and she stalled. Got her going but she idles a little rough. Another old Johnson 50hp next to me purred like a kitten. I am thinking it is the stator or timing base since everything else has been rebuilt or changed. I am ready to buy an impact gun to get the flywheel off. Also I tried a sterring wheel puller from Autozone and the threads do not match. My compression is 109, 104, 108.
Any help on the flywheel would be helpfull. Someone said to wrap a towel around the flywheel and hit the ratchet with a hammer to jar the nut free. A screwdriver slips off the flywheel and doesn't work when wedged against the block. I have to find a flywheel puller to with the right threads. Thank You

 

[jtexas]

Re: 1977 70HP Evinrude will not go

Hold the flywheel steady with a piece of bar stock bolted to the top.

Before you start buying more parts, though, get an inline spark tester (couple bucks at autozone), set it for 7/16", clip it to the engine block, attach the leads (one at a time), look for a strong blue spark.

Not sure what the timing at 2500 RPM is going to tell you. You can use the procedure described in the thread linked above to set WOT timing, but that has nothing to do with your bogging.

Are you using champion QL77JC4 gapped at .030?