1974 Evinrude 70hp stalls into gear.

[sycostang67]

We took our boat out for the first time the other day and for the most part it worked great. The only issue we had was it stalled 2 of the 3 times we were trying to get underway. It was fine when we launched, I let it idle for 2-3 minutes before taking off. When we went to leave our dock later on, I again let it warm up for 2-3 minutes and when I put it in reverse it died. It took 2-3 tries to fire it up again but then it went into gear just fine. We cruised for about 20 minutes then went to load up on the trailer. I shut it down, went and got the trailer and started it back up, put it in reverse and it died again. It took another couple tries for it to fire and then I loaded it up. The only constant was it usually seems to happen when going to reverse. I was wondering if bumping the idle up just a tad would help. It seems awfully quiet at idle that I'm afraid it's going to stall because I can't hear it running. As I'm typing this out I realized I don't really recall what speed it was idling at. I can put the muff on it and fire it up though, what speed should it be idling at?

 

[jbuote]

Not a pro here, but pretty sure you want 650 -750 RPM at idle, in gear, in the lake.
If you're going to try and set it on muffs, I think you'd want to see about 1100 - 1150 (ish) RPM.

If you set it on the muffs, you'll still want to check and reset it once on the lake.
Muffs are "Ok" to get close, but then you want final settings done on the lake under load.

That's a general baseline anyway..
More experienced folks here could let you know more details than that..

Hope it helps!!

 

[sycostang67]

That gives me a place to start, thanks.

 

[sycostang67]

I went and put the muff on and fired it up, it seems to idle about 1300 rpm right now. We are taking the boat back out tomorrow though so I will check it in the water and pay attention this time. I do have one other question though, not sure if it's related. There are some holes on the lower drive unit. I cleaned some stuff out of them that appeared to be an old wasp nest. I noticed it was full again today so I cleaned it out again. I ran the motor and it filled up some more so I cleaned it a 3rd time. I continued until it would no longer fill up with the motor running. Could these holes being plugged have caused my issues?

 

[fireman57]

That is where the water to cool your engine enters so you were probably over heating. make sure they stay clean and run again and check the temp

 

[jbuote]

That is where the water to cool your engine enters so you were probably over heating. make sure they stay clean and run again and check the temp

Hmmm....
I thought those were water outlets... The inlets should be under the muffs, and vertical no? (Like I said.. I'm not a pro.. LOL)

 

[jhetrick55]

This are definitely where the water is going to enter your engine. Do make sure they're clean or you may overheat the engine. jbuote is also correct that you want to set the idle out of the water, in neutral at about 1000-1100 rpm. In gear in the water should be about 650-750. Hope it goes well!

 

[racerone]

No those are NOT the water intake holes for the cooling system !!

 

[jhetrick55]

racerone - where the muffs are covering are the inlets are the intakes. Sorry, not the circled holes.The circled one is the water outlet. Either way, making sure the inlets or outlets are clear is necessary.

 

[sycostang67]

We took the boat out today, in the water in neutral it currently idles at 1200rpm, and drops to 1000rpm when put in gear. When we first took off, it stalled into forward gear and when I was increasing the throttle it felt like it bogged a bit. I also neglected to really let it warm up much. When we were leaving the other dock though, I let it warm up a bit longer idling at 2000rpm(neutral throttle) and I didn't have any issues going into gear that time. I'm thinking maybe I just wasn't letting it warm up enough before. I imagine we will be out again later this week so I can try some more.

Another thing I was wondering is how do I know if the tachometer is giving me a correct reading? The original motor was most likely a 90hp 4 cylinder Johnson. Would the lack of a cylinder change the reading? I know some aftermarket auto tachometers have to be set for the number of cylinders they are being attached to.

 

[jbuote]

The original motor was most likely a 90hp 4 cylinder Johnson. Would the lack of a cylinder change the reading? I know some aftermarket auto tachometers have to be set for the number of cylinders they are being attached to.

Yup!
You need to set your tach to appropriate settings for what engine you have now..

in the water in neutral it currently idles at 1200rpm, and drops to 1000rpm when put in gear. When we first took off, it stalled into forward gear and when I was increasing the throttle it felt like it bogged a bit. I also neglected to really let it warm up much. When we were leaving the other dock though, I let it warm up a bit longer idling at 2000rpm(neutral throttle) and I didn't have any issues going into gear that time

Shifting at the RPMs you listed would result in GRINDING/CRUNCHING gears as far as I know...
Your tach is off.
If shifting is pretty smooth, but you keep dying, I'll bet your rpm is still too low, but your tachometer isn't set properly so it looks high..

I'd stop any other troubleshooting in the shifting area until you've verified your tach is correct.
Either that, or buy/borrow/rent a timing light with tach, or an optical tach or some other tachometer you can verify with.

If a second tachometer verifies the reading you posted, then something else is REALLY wrong..

I'll stop here, and leave you in the pro's hands.. I might not have all of this right.. LOL

 

[flyingscott]

What is your compression? Have you done a spark test yet?

 

[sycostang67]

There's no grinding/crunching when going into gear, just a light thunk sound.

I haven't done any mechanical tests, the place I got the boat from said they do a leak down style compression test on every motor, If it loses more than 10% of the pressure over a given amount of time they won't sell it. I do have a spark tester so I can do that. I'll also pop the tach out to see if it's adjustable. If it's not, I assume I will need to get a tach that can read for 3 cylinders.

 

[oldboat1]

If you are having trouble cleaning out old nest materials, drop the lower unit and clean/flush up in the leg and the lower unit (some flushing at least). May be surprised what you find in there.

 

[flyingscott]

Good luck with your motor

 

[sycostang67]

I got under the dash and the tach was adjustable, I now have it set for 3 cylinders. Now, neutral idling out of the water it's at 850rpm and in gear it's 800rpm. I had a brain fart and forgot what I was supposed to set it at and then got caught up cleaning the gauges and ran out of daylight. There was so much dust I could barely see the mph gauge. I'll get it adjusted tomorrow and out to the lake again this week for a submerged test.

 

[sycostang67]

I got the idle adjusted to 1000rpm on land last night and took the boat out this afternoon. Idle speed in water is now 800rpm, I had no stalling issues or noises going into gear. It's also nice to know I'm not doing 4k rpm at 20mph now. I'm now turning 2600rpm at the same speed. Thank you guys for all the help in getting this figured out, taking the boat out will be a lot more relaxing not having to worry about this anymore.

 

[jbuote]

NIce!!

I'd still adjust the idle back down to 650-750 RPM next time you're on the lake with it.
Then it's whatever it is at home on the muffs or in a barrel..

Also, I'd do the compression and spark test as well as flyingscott mentioned.
Even though it may not be an issue, it's ALWAYS a good idea to do it. Even now that it seems to be running pretty good, you'll want those readings in case of an issue later.
You'll know if compression has reduced or spark is worse then it is now etc... or it could even tell you if you should expect any issues in the near future (low compression for example would run, but might not last...)

I did baseline checks on both engines I have and recorded the results for comparison later if I have any issues.
Also... A leakdown test on a 2 stroke doesn't really mean much at all. Helps a bunch on a 4 stroke, but not so much on a 2 stroke.

It's the compression numbers you really want.

Glad it's working out! :thumb:

 

[sycostang67]

All right, I'll break out the compression tester this weekend before we take it out again. I guess it would be nice to have a base line that way I can tell if something has changed later.

 

[Inland Fiber Classic Boats]

I agree with oldboat 1 start there work your way up..