1977 Evinrude 70 HP: Trouble idling in water and cannot reach WOT

[SHSU]

Thanks racerone ,
Glad I asked the question on the fuel line change. Any thoughts on why forcing gas through might cause the increase in RPM at high pressure? Gummed up carbs?

As for your other questions:

"Rebuild": I didn't do a true rebuild. Didn't crack the case and redo the cylinders. But took the powerhead off the outboard and opened everything else from the exhaust to head. Put in new gaskets and cleaned out those areas.

Flywheel key: checked and verified that TDC of Cylinder 1 is TDC.

Orange Wires: Checked that. Had the engine achieve WOT on first outing on this power pack before this issue started. The second time out, engine started up just fine, idled out achieved WOT then when I slowed down again, engine died. Haven't been able to achieve WOT since then. That was 3 or 4 trips ago.

Reed Valves: I will be checking those again when I pull the carbs off to reclean. One thing I noticed on this last trip was a lot of blow back out of the air box early. Then it stopped. So will be looking at those.

The change in RPM noticed was before I corrected the timing. I haven't checked that again and forgot to check. Glad you mentioned that.

Any other suggestions, please let me know

Thanks again,

SHSU

 

[oldboat1]

Is there still evidence of water intrusion on the top cylinder? In combination with gasket replacement (which you have done), you will want to resurface the head cover to insure there isn't any warpage.

As I understand relocation of the tell-tale elbows, the top of the powerhead (your location) is acceptable, as well as the top of the cylinder head. As you also have a sender in the powerhead, maybe the bleed off from the tell-tale affects the gauge reading(?). And in any case, there obviously can't be any intrusion allowed into the cylinder -- something you might want to confirm. The sender typically has to be matched to the temp gauge (eg. VDO to VDO).

What was the indication that the rectifier went bad? Would lose battery charging, but was there a change in tach operation at that point? Is boat speed commensurate with low rpm readings, or does it seem as if the boat is moving along faster than the tach would indicate?

Guesses, of course. Getting good feedback but seems no success quite yet....

On the carb cleaning --- be sure you run soft wire or mono through the h.s. jet on the bottom, then carb spray. Additionally, the nozzle gaskets need to be in place for the the carb to draw properly.

 

[Tim Frank]

Have you replaced the fuel lines?
They do deteriorate internally over time and can shed debris that will gum up the works.

 

[SHSU]

Howdy Oldboat 1
Appreciate you stopping by. Answers below:

Water in cylinder: After the new gasket install, I checked and didn't see any. But will check again when I pull the carbs off to see if I can see carbon build up or any water evidence on the spark plug after this last outing.

Cylinder Head: When I pulled the head, I checked with a straight edge to make sure there was no warpage. Didn't resurface as I didn't see any warpage across the faces

Temp Gauge: Possibly, I am not sure. This last time I shot it with my thermal gun and it was coming in at ~110-115. Didn't try it while on the water yet as temp gauge still read the same as when in driveway. Also, the sender and the gauge were bought as a kit, so both are matched.

Rectifier: When I replaced it, it had exposed wiring and no spark was being created.

Tach: Believe it is reporting accurately. Seems consistent with the speeds we are achieving. At 2000 RPM we are getting 5.5 MPH. Can't get up on plane.

Howdy Tim Frank

I replaced the hoses during the initial rebuild and have checked them again by blowing air through them. But when tearing apart the carbs will be checking all of those again as well.

As always, much appreciated

SHSU

 

[racerone]

In my opinion it should not be hard to figure out what is wrong here.

 

[SHSU]

In my opinion it should not be hard to figure out what is wrong here.

I am hoping so too. Only wish there was a way I could load test easily at home. I have looked at getting a loading prop, but can't find one for this engine. Think it would be worth it as I have to drive ~1 hour and 15 minutes to put the boat in water. So if I go out, we are looking at making a day of it, as best we can regardless if the engine is working well or not...

SHSU

 

[oldboat1]

Kind of a complex post, so might have missed a response. Did you try a drop-cylinder test at higher rpm. If not, you might try that with a timing gun. Attach sequentially to each plug wire, and see if the flash stops while running -- would indicate no fire on that cylinder. As you are a hike from a body of water, try it in a large plastic garbage can filled to the brim, and keep the hose running -- might have to brace the can. Bump the rpm and see if you get a spark drop. It may actually be happening, if at all, before you notice it at 2K rpm.

[edit. Revisited your test barrel pic -- you might either raise the barrel or lower the stern. Get the leg as deep as you can.]

 

[SHSU]

Howdy oldboat1,
I did not check any of the other cylinders at ~2k RPM (other then Number 1 Cylinder) with the timing light. Did that to see what my timing was set at.

I will try that as you suggested to see if I see any drop in cylinder 2 or 3.

Also when I test in the "barrel", I am not putting the engine in gear. Should I? Also, if I am putting in gear, I am guessing prop needs to be on to provide a "bite" and load on engine.

Thanks,

SHSU

 

[oldboat1]

I do it with the prop on. Before you do the test, let the engine run until it warms up. Test in gear -- fairly short bursts should be sufficient to see if there is spark drop.

 

[SHSU]

Howdy All,
Sorry it has been so long without an update.

As recommended took apart my carbs and looked at all the reeds

Cylinder 1


Cylinder 2


Cylinder 3


See no issues with the reeds on any of the cylinders. Also the carbs looked very clean as well.

I decided to look at the air manifold.... Realized that I didn't torque the bolts... :facepalm::facepalm::facepalm::facepalm::facepalm:

Suspect that was the issue..... To much air being sucked in from other areas then the carbs.

Took the boat out Saturday and had to adjust the timing, but...

Once timing was fixed and adjusted the link/sync she ran beautifully!!!!




With the new 15 degree prop, was able to get RPM to 5200 at WOT and the boat full of fuel, 2 adults, 1 child, dog, fishing gear, and full tank of gas. Didn't notice any temp issues, this time but will keep an eye on it.

Just want to say thanks for everyone chiming in and helping.

Until next time

SHSU

 

[oldboat1]

Good success story -- Thanks!

Happy Boating :thumb:

 

[MoNeM]

Very interested in this thread as I have the same motor 70773s the only difference is that my linkage is horizontal and not at 45 degrees as yours. I to have the problem that the motor does not idle and therefore I cannot get into gear because the this.. I am hoping that the remedy (Air leak) will also solve my problem