77' 70HP Evinrude Dies/stalls at 2k - RPM - FIXED!

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Numlaar

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Hi all,

I have 1977, 70HP evinrude 2-stroke, 3cyl. (running it on a 15ft fiberglass trihull that weighs maybe 500lbs). I don't know what prop pitch, as the prop is not labled, but appears original.

The motor sat for probably 10+ years unused. I have done a major overhaul on it, and done the following:

Rebuilt carbs (tanked, cleaned, rebuilt with kits)
new spark plugs
New coil packs
Seafoam decarb (yes it was NASTY), but seems clear now.
(ton of stuff to the lower unit but that doesnt apply to my issue).

Compression is:
120 #1 (top)
110 #2 (middle)
125 #3 (bottom)

The problem is this:

When I go to take off the motor goes, bleehhhhh (hard to describe the sound, almsot like a vacuum cleaner sucking really hard), like it's either starved for fuel/air or flooding, then it will either conk out, or slowly start to take off, (RPM's build little by little, till vroom, then it seems fine)...

This is worsened, when say, I am idling down a channel for a while, then go to take off, it can take up to 2 mins before the engine starts to "go". When this is happening, I will get maybe 2k rpm out of it. it will chug along, then suddenly it will take off and be fine again... work great until I let it idle down then problem starts over.

When I don't let it idle down for long, it seems to work just fine, like if I go WOT, down to idle, come off plane, then take off again (fairly quickly), there is no issue, and it runs just fun, takes off just fine... its only after it idles for a bit that it becomes a problem, then wont go.

Motor will always instantly restart afterwards.

When it does get going, and gets up on plane, WOT is 5200rpm (not sure if thats good or bad), with me in it (200lbs more). I dont have a speedo, so don't know how fast I am going.

It also "seems" to be using a lot of gas.. this is the first time I have had it in the water, but test running it around yesterday I went through 8-gallons in about an hour... (running between WOT and idle while trying to figure out this issue).

Any thoughts?
 
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Numlaar

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

One friendly bump looking for a reply, then I'll check back tomorrow....
 
D

DJ

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

You have "synch/link" and carburetor issues.

Take it back to whomever tuned it.

DO NOT run it that way.
 

jonesg

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

Try choking it when it goes bleeehhhhh :D
if it responds with power then its starving for fuel.

Did you rebuild carbs with new carb kits?
You may have missed something in the carb job.
 

Numlaar

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

You have "synch/link" and carburetor issues.

Take it back to whomever tuned it.

DO NOT run it that way.

well that would be me... sooo.... :) any suggestions on what I should look for?
 

Numlaar

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

Try choking it when it goes bleeehhhhh :D
if it responds with power then its starving for fuel.

I'll have to try this tomorrow and let you know

Did you rebuild carbs with new carb kits?
You may have missed something in the carb job.

I realized that, pulled em back off.... (had the carbs off it 3x now), ran through them all again, and don't see anything wrong... there isn't really much to these carbs... its orifices top/bottom, so there arent even needles in it. Just the float valve... which works fine, all 3 pass the air hold test, and there is no visible fuel leaking...

Its also, new gas tanks, new hoses, new bulb, new filter, new pump, and yes the vent is open on the tank.

Like I said, it is just fine if I don't let it idle too long... but when it does, it chugs for a while then goes again... and seems fine after...

Any idea what I should be physically looking for in the carbs?
 

jonesg

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

Did you get the high speed and idle jets mixed around?
Its not hard to do.
 

Numlaar

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

Did you get the high speed and idle jets mixed around?
Its not hard to do.

No, these were done one at a time, and made sure they matched #'s for each.

It will run WOT, just has a huge hesitation to get there after idling for a while... once I get it WOT and run it and let it come back to idle and take off right away its fine, it only happens after I have been idling for say 2 mins +, then it chugs and bogs and takes some time to get up and go again.

While reading various other threads on the issue a few mention a possible crank seal problem? The motor did sit a long time, and in fact was sort of "locked up" when I got it, I had to pull the plugs, and oil the cylinders and let it sit for a few days and then turn it over by hand to get it freed up. (never torn into the actual powerhead)...

Once I freed it up, it started and initially would only idle... ( NOTHING above 2k rpm), once i rebuilt the carbs it was able to go WOT but developed the problem it has now, so its a definite improvement, but still not 100%.

One other thing I noticed while checking it, was the timing advance seems "sticky" like its moving through pancake syrup... is that how its supposed to be? is there a way to lube that without taking the whole thing off? (From the looks of the spring I dont wanna mess with it coming apart on me)
 

Numlaar

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

Good morning folks!


Try choking it when it goes bleeehhhhh :D
if it responds with power then its starving for fuel.

I will be sea trialing it here shortly, and let you know on this one...

In the meantime, regarding my timing arm advance question:

Here is what I am talking about:

Timingarmwitharrow.jpg


On the pivot bolt, the grease is really old (33years anyone?), and the arm while it is synced and moves with the carbs, it moves very slowly, and feels "sticky"...

1. could this be contributing to the hesitation/bogging problem I am having?
2. If so, how do you lube this? Like i mentioned previously, I am a little leary of pulling the bolt, and have the tension spring fly out (never had one of these off before).


Also, as mentioned, I de-carbed it with a can of sea foam, but I am still getting this:

Carbon.jpg


This motor sat forever! So again a couple questions:

1. Should I run another can through it?
2. Could this (carbon buildup) be contributing to my problem?

Thanks in advance!

I will check back in a bit after the sea trial and let you know the answer about the choke soon.
 

Numlaar

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

Try choking it when it goes bleeehhhhh :D
if it responds with power then its starving for fuel.

OK just got back from the sea trial, and tested this.. here is what happens:

Starts right up, warm it up and idles fine...
Take off at just above idel (1500RPM) and its fine
Get to the channel and nail it, bogs and dies
If I very slowly creep the throttle up, it will chug/bog from 2k RPM to 3kRPM, then vroom takes off
If I "plow along" at 2k RPM, just where its wanting to die, and a very quickly burp the choke, it will decrease RPM to about 1800, then increase to 2500, then settle back down to around the 2kRPM mark and start to chug again...

Burp the choke again, same thing...

If I burp the choke to get it through the 2-3k RPM range I can go to WOT.

So it DOES seem like it is starving for fuel...

I also did the hand test for each carb, got gas from each...
When applying the choke get gas from each carb as well... so it "seems" like its getting plenty of fuel, but obviously has a severe problem in the 2-3k RPM range.

Any suggestions now on what to look for???
 

patrick4266

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

I had a similar problem, just got it running right yesterday. I rebuilt carbs, still did the same thing took then back apart a few times, new primer bulb, reset the floats,lync and sink,every thing i could think of. I would try to go and it would fall flat on it's face. Bought a parts motor for 150 changed carbs and it runs great. I think i must of had a internal leak in one of my carbs or i did something wrong in rebuilding them but I have rebuilt a lot of them and they worked fine.
 

Numlaar

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

I had a similar problem, just got it running right yesterday. I rebuilt carbs, still did the same thing took then back apart a few times, new primer bulb, reset the floats,lync and sink,every thing i could think of. I would try to go and it would fall flat on it's face. Bought a parts motor for 150 changed carbs and it runs great. I think i must of had a internal leak in one of my carbs or i did something wrong in rebuilding them but I have rebuilt a lot of them and they worked fine.

I have a very similar motor (mine is a 1977 70 Evinrude)... I also have a 1976 Johnson 75HP Stinger...

Do you think swapping with these carbs would be ok?

The main issue is, they haven't been rebuilt, and have been sitting for an unknown number of years, also, they look identical, but according to the book they are actually different part #'s (no tags on the carbs themselves to verify) ... I am assuming because of Orifice sizes or some such. I just don't want to put them on and risk damage to the motor.
 

Numlaar

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

One friendly bump tonight for the evening crew...

outstanding questions:

1. The choke test while running did increase the RPM's which indicates a fuel starvation issue (between 2-3k RPM). What else should I check or look for?

2. Would it be worthwhile, (and OK), to swap the carbs with the carbs off a 1976 75HP Johnson Stinger?

3. Could carbon buildup be an issue, and should I run another decarb (see picture above)?

4. Could the timing arm feeling "sticky" be an issue, and is there a way to lube it? (see picture above)

Thanks for any additional information or direction on where to go with this!
 

patrick4266

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

I have a very similar motor (mine is a 1977 70 Evinrude)... I also have a 1976 Johnson 75HP Stinger...

Do you think swapping with these carbs would be ok?

The main issue is, they haven't been rebuilt, and have been sitting for an unknown number of years, also, they look identical, but according to the book they are actually different part #'s (no tags on the carbs themselves to verify) ... I am assuming because of Orifice sizes or some such. I just don't want to put them on and risk damage to the motor.

Some one that knows more than me will have to answer that one for you. I have a 83-70hp and took the carbs off a 85-70hp, they work good. I don/t see how it could damage the engine.
 

Numlaar

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

Some one that knows more than me will have to answer that one for you. I have a 83-70hp and took the carbs off a 85-70hp, they work good. I don/t see how it could damage the engine.

Too lean of a condition will easily burn a piston on a 2-stroke, so I want to be sure before I swap them out...

but thank you for being honest, I would rather play it on the safe side. :D

So I guess that puts me back to my last post, with questions 1-4 needing some answers!

1. The choke test while running did increase the RPM's which indicates a fuel starvation issue (between 2-3k RPM). What else should I check or look for to determine the cause of the fuel shortage?

2. Would it be worthwhile, (and OK), to swap the carbs with the carbs off a 1976 75HP Johnson Stinger?

3. Could carbon buildup be an issue, and should I run another decarb (see picture above)?

4. Could the timing arm feeling "sticky" be an issue, and is there a way to lube it? (see picture above)
 

Numlaar

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

Still looking for some guidance on where to go with this motor... :(

Thanks
 

Numlaar

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Re: 77' 70HP Evinrude Performance issue

Re: 77' 70HP Evinrude Performance issue

OK well since I am not getting any feedback, I went ahead and did the following:

Left the original carbs on the motor, and put on a new fuel pump... NO CHANGE

Took the carbs off the 1976 75HP Johnson stinger, and swapped them on to my evinrude (only difference that I could determine was the high speed Jet # was a 55d instead of a 54D)... but still NO CHANGE

I do not see how two completely different sets of carbs can produce the same results, unless its something else that is causing the problem... still same issue... have to burp the choke to get it through the 2-3k RPM range, (to keep it from leaning out and dying), otherwise runs fine.

I am really desperate here.. I have one week to get this boat water ready... Please anyone, someone, toss me some guidance??? (I can't afford to take it anywhere).
 
D

DJ

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Re: 77' 70HP Evinrude Dies/stalls at 2k - RPM

Re: 77' 70HP Evinrude Dies/stalls at 2k - RPM

The "triple loopers" are very sensitve to "Synch-Link" adjustments. If you have not done that, per the OEM manual, you are jousting at windmills.

I've burned up a couple 3-cyl. "loopers" by ignoring that, amongst other things.:(

That engine has to have ALL THREE cyl's. hitting 100% or it will bog and die.

Something is is missing here:

1. Compression.

2. Spark-at the right time.

3. Fuel-through ALL jets.

4. Fuel and timing synch.

We figure out which one and we have it.:)
 

Numlaar

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Re: 77' 70HP Evinrude Dies/stalls at 2k - RPM

Re: 77' 70HP Evinrude Dies/stalls at 2k - RPM

The "triple loopers" are very sensitve to "Synch-Link" adjustments. If you have not done that, per the OEM manual, you are jousting at windmills.

I've burned up a couple 3-cyl. "loopers" by ignoring that, amongst other things.:(

That engine has to have ALL THREE cyl's. hitting 100% or it will bog and die.

Something is is missing here:

1. Compression.

2. Spark-at the right time.

3. Fuel-through ALL jets.

4. Fuel and timing synch.

We figure out which one and we have it.:)

1. Compression was noted in first post:
120 #1 (top)
110 #2 (middle)
125 #3 (bottom)

2. ?

3. Has to be... I have checked and re-checked and triple checked the carbs, and like I said, even took a set off another motor and got exact same issue, just no way that 6 carbs can all be bad. Pulled em open again to be sure, and they are spotless... can take carb cleaner in a spray can, and spray it through all the jets without any problem.

4. The Linc & sync was done a while back, I dont have a book for it, my neighbor did it... I also don't have the money to get a book right now (I have 7 dollars to my name)... can you post the steps or send them to me?
 

Numlaar

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Re: 77' 70HP Evinrude Dies/stalls at 2k - RPM

Re: 77' 70HP Evinrude Dies/stalls at 2k - RPM

Update:

Got the steps and the Link & Sync Didnt help. Still does the same thing.

I went ahead and pulled the Whole side assembly, with the timing arm, etc. cleaned and lubed it, and got that working better, this seemed to help a little, but it still wants to die when trying to throttle up.

I read this on another forum for a motor with the same issue:

"problem is lower part of cylinder is losing compression causing loss of crankcase pressure. There is a test for that. Remove plugs an rotate piston to top. Then place your thumb over the hole and rotate it quickly down and see if a vacuum will form enough to make a pop when you remove your thumb. Common problem in those motors which will mean a rebuild to include boring.

Another good indication is it will idle for a little while and then die. The primer bulb will stay hard but you need to choke it to restart it. Then, if you tap the choke and it takes off, then it runs fine.

Put your thumb over the spark plug hole and draw the piston down for each cylinder. If it doesn't suck, then it needs a rebuild. Don't do a compression cause it can have 125lbs compression and still need the rebuild. The fault is at the bottom of the stroke, not the top. The stroke down is what builds crankcase pressure which pushes gas into the cylinder. No downstroke pressure and engine will stall."


I am unable to perform this test myself, as I need someone to bump the key for me while I thumb the spark plug hole.

Do you think this may be it, and the motor is just "done"?

Still looking for ideas on this thing...
 
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