1987 Evinrude 70hp wont idle under 1100rpms

[bgphill]

I bought this motor from a guy who said he was having idle problems. I figured for 300 bucks and a little work I could solve the problem and get a great motor for my boat.

Here's what the motor does. Idles just fine on the muffs or in the river out of gear at 1100rpms and at 850rpms if you back off the idle that far. I set the idle out of gear at 1100rpms. When you put it in gear, if you don't bring it up past 1100rpms quick it will die. It runs just fine throughout the rest of the rpm range and at any speed off idle. Key primer doesn't help much. You do have to key prime a bit and throttle up to get it to start when hot. All three carbs show signs of spitting back a little fuel into the air box. I read that some of this is normal (adjusting the floats has no affect). Checked the needles and seats twice (all good).

I have so far rebuilt the carbs (total tear down twice) link and sync on the install 3 times, replaced the stator and rectifier (it had been cracked and melted), replaced the leaking VRO with a standard fuel pump #438559, new fuel lines and primer ball from the tank, new tank vent, new water fuel separator, new champion plugs (tried gapping at .030 and .040), compression is 120 across the board, new plug wires, ran ohms checks on the timer base, stator, rectifier, coils (all within spec), ran a spark check several times at 7/16" gap (all good) temp sensor tested good and the battery is new.

I found a post by Dhadley that fits my issues for a 1978 70hp motor and he replied that these motors have reed valves that stiffen over time that create this problem. I have stainless steel reeds (probably the originals). Could this be my problem? Could this stiffening also cause blow back in the air box by not allowing the fuel to pass by? If I need new reeds then what's the best?

Help???

 

[bgphill]

Re: 1987 Evinrude 70hp wont idle under 1100rpms

Still no replies on this issue but I will add an update. I removed the intake and inspected the reeds. None are bent, warped or broken. I can however see small cracks of light at the tips where the reeds meet the reed box. The light gap is larger on some leaves than others but none are more than .010. I've heard you should see no light. Does anyone know how much gap is allowed between the reed and the red box if any?

 

[R.Johnson]

Re: 1987 Evinrude 70hp wont idle under 1100rpms

All that! And no compression test on a 1987 motor.

 

[R.Johnson]

Re: 1987 Evinrude 70hp wont idle under 1100rpms

Sorry, I mis-read the post, you did a compression test

 

[FishHunt23]

Re: 1987 Evinrude 70hp wont idle under 1100rpms

For what it's worth, I've got a rebuilt 1988 70. It was a salvage-type buy not unlike yours. I've done a ton of work on it (many of the same things you mentioned) and had the carbs and cylinders professionaly rebuilt and the crankshaft replaced.

I don't have a tach on the boat so I can't quote RPMs, but I have the same problem as you. It starts and runs very well, but won't stay running at low RPMs in gear. I can go maybe 30 seconds at the slowest speed (guessing 800 RPMs or so) but then it will stall and I have to prime to re-start. If I bring it up to about 1200 RPMs right off the bat it runs like a champ and I get smooth accelleration to top speed.

I know this post isn't much help, but misery does love company... I'm a fisherman, and my biggest complaint is that I can't troll with it. I will soon be looking for a buyer than doesn't care about trolling!

 

[bgphill]

Re: 1987 Evinrude 70hp wont idle under 1100rpms

Thanks for the company FishHunt23. Did you replace the reeds in yours? I looking at ordering a set of Boyesen reeds from bobsmachine.com as a final straw. Here's a link to the dhadley post I found. Maybe it will help you.

http://www.outboardmotor.biz/t/015575.html

 

[bgphill]

Re: 1987 Evinrude 70hp wont idle under 1100rpms

Hey FishHunt23, do you have fuel spitting back out of your carbs like I do and is your fuel economy absolutely horrible like mine? Reeds is the only thing I can come up with. I guess I'll break down and just do it unless you or anyone can think of something else to look for.

 

[FishHunt23]

Re: 1987 Evinrude 70hp wont idle under 1100rpms

Sorry I didn't respond earlier.

I didn't do the rebuild, so I can't comment on the reeds. However, the carbs do spit a little fuel and the economy isn't great. But then again, I don't have experience with a similar motor to compare it to for fuel economy.

I am living with the problem for now. If you do find success by replacing the reeds, please let me know. I think it's a good guess as to the problem.

John

 

[bgphill]

Re: 1987 Evinrude 70hp wont idle under 1100rpms

I finally have it nailed down. It's a bit lengthy but the process warrants explanation. I took the intake manifold as it were off and inspected the reed blocks and reeds. When you hold the blocks up to the light looking through where the carb would mate, you can see a thin slit of light between some of the reeds and their corresponding reed block. The reeds appeared to be in fine shape, no cracks, warps, chips or bends. I took the reed assembly into the mechanic that I ordered my new intake gasket from for his opinion. He inspected them and came to the same conclusion. They're fine. He did mention that my issues could have come from a leaking intake gasket. I didn't notice anything when I removed the intake but then again the gasket did not come off the motor and was worn and separated around each of the reed blocks where they attach to the manifold. I was going to order new reeds anyway until I found out they're two months out to get. I took my old reeds off the blocks, cleaned them and carefully tried to bend the ones that I felt could stand some adjustment. I made sure I didn't flip them when reassembling. I put the whole works back together with a new gasket and perfectly clean mating surfaces and viola, a quick link and sync an idle timing check and I had my idle back at 750rpms without dieing. Just so everyone that reads this post understands that although this has appeared to solve the idle problem, I'm still not enthusiastic about this motor. It still seems to burn a lot of fuel and it's no inboard.