70 hp, Thought I had it fixed BUT NOT

[roger3645]

Okay this is what I have and what I have done. I have a 1991 70hp Johnson. It?s new to me since Jan 08. Compression is 120 psi on all three. I have decarbed the motor with 2 treatments of sea foam, and replaced the plugs. I have blue spark that will jump a 7/16 gap. I took apart and clean the carbs and have a really good firm primer bulb. Reset the link and sync per the manual.

1st problem poor idle, poor top end and fouling the plugs.

Problem was a bad thermostat, the spring inside thermostat was broken. New spring and new thermostat. Idles well and does not foul the plugs.

Problem is it surges at WOT or anything above 4500 rpms and when she surges it feels like it wants to go for a second then bogs down. Now I?m thinking it?s starving for fuel, float drop may be to low. When I had the carbs apart I turned them upside down, there was about an 1/8 inch space between top of float and base of the carb. Is this TOO Much????

Second problem: This has happen twice, once before I replaced the thermostat and once after. It was currently running like this when I last shut it off. Will not idle under 2000 rpms kind of like an automatic choke stuck on a car. Nothing I could do to get the idle back down. Could this be a bad electric primer or something like that. Well I guess I could have taken the primer apart and cleaned it. As I?m thinking about the primer, it has a red switch (or lever) that is set parallel to the solenoid. When the motor is running and I move the lever down to the 6 o?clock position it will shut the motor off. Is that normal ?

Any information will be greatly appreciated!

I thought the thermostat was the only thing wrong but I was wrong

Thanks
Roger

 

[tashasdaddy]

Re: 70 hp, Thought I had it fixed BUT NOT

the primer is a valve that allow fuel into the intake, it is operated by pushing in of the key. you never have to turn the knob, unless the battery is dead, and you are rope starting the motor. this picture is the normal postion for the red lever. when you move it you are flooding the motor with fuel.

check and make sure the timer plate is moving freely, could be getting hung up, causing the high idle. also when surging is you primer bulb collasping, this would be a fuel restriction from the tank, possibly clogged vent.

 

[Dhadley]

Re: 70 hp, Thought I had it fixed BUT NOT

With the carb body upsidedown the float should be parallel to the gasket surface.

What spark plugs are you using?

 

[roger3645]

Re: 70 hp, Thought I had it fixed BUT NOT

I'm using the recommend plugs CJ4 , gapped at .030. The timer plate is not hung up and moves freely. Got an e-mail from previous owner. He said had same problem in the past with missing at top end. It was the hose from the tank to the motor. I'll check for restricted fuel line. Hope it is that simple.

 

[jtexas]

Re: 70 hp, Thought I had it fixed BUT NOT

you need a resistor-type plug to suppress the radio frequency interference with your electronic ignition - use QL77JC4

 

[ezeke]

Re: 70 hp, Thought I had it fixed BUT NOT

Your engine started life with the QL77JC4 and that is still the recommended spark plug:

http://www.boatsetup.com/SparkPlugChart.pdf

 

[roger3645]

Re: 70 hp, Thought I had it fixed BUT NOT

Yes those are the plugs I'm using. Just could recall all the numbers off the top of my head. Pickedup a new fuel hose from the tank to the motor. I'll try it out on Tuesday or Wednesday. Aren't those great days off?? LOL.

 

[roger3645]

Re: 70 hp, Thought I had it fixed BUT NOT

Okay I hooked up the new fuel hose from tank to motor. Started it up and it still will not idel below 2200 rpms. The butterflies on the carbs are closed. I disconnected throttle linkage backed the idel timing screw all the way out. Idel mixture screws on each carb are set at one turn out from lightly seated. There is no binding on the timing base or throttle control arm of the motor. I know I am grasping here but could it be low fuel level in the tank? It's a 10 gallon tank but there may be only 2 gallons in the tank. I also ran it with the gas cap off so it can't be a venting problem. Or could it be a restriction in the fuel pickup in the tank causing too much pressure? I'm guessing here, but I'll run it on another tank in the morning. DOes this motor have a quick start or something like that. I took apart and clean the electric primer. Any help out there????? I'm lost!!!

 

[clanton]

Re: 70 hp, Thought I had it fixed BUT NOT

While you are getting the bugs out, you should locate the service bulletins for this engine and do the updates. One for waterpump, relocating of tattle tale hose, change of thermstat spring and cover, carb jet and timing kit, temp sender change. The temp sender pigtail should have tan wire with blue stripe. After the engine is running, it should be proped to turn 6000 rpms.

 

[clanton]

Re: 70 hp, Thought I had it fixed BUT NOT

mixture screws out one turn not enough, may need 3-5 turns.

 

[clanton]

Re: 70 hp, Thought I had it fixed BUT NOT

The fixes are,
SB2221 temp sensor, pigtail tan/blue stripe
SB2225 thermostat seat
SB2271 jet kit/ timing change
SB2276R1 relocation of tattle tale nipple
432955 waterpump kit has different inpeller, thermostat housing cover, spring, and inclueds SB2276R1

 

[roger3645]

Re: 70 hp, Thought I had it fixed BUT NOT

Thanks I'll check on the updates.

 

[rickdb1boat]

Re: 70 hp, Thought I had it fixed BUT NOT

When it dies, pull the plugs and see what their condition is. Wet or dry? I have my 91' 70 HP carbs set to 3 1/2 turns out. You might want to adjust the plug gap to .040 instead of .030 for a better idle. It will not affect running at other speeds. But it should still idle well at the current spark plug setting...

 

[rickdb1boat]

Re: 70 hp, Thought I had it fixed BUT NOT

Also, when you cleaned the carbs, did you remove the high speed jets (Oriface) and clean them as well? Spray carb cleaner in all passages and then blow out with compressed air? If not, you may still have a clogged carb. That's what it sounds like from your description...

 

[roger3645]

Re: 70 hp, Thought I had it fixed BUT NOT

Yes I cleaned the high speed jets. I will moved the gap to .040. I stared it up today using another tank but same high idle. Moved the idle screws to 3 turns out, lowered idle now very ruff and alot of unused fuel coming out the exhaust. I'll take he to the lake in the morning. Manual shows 1 turn out for idle mixture screws. But I'll give it a try at 3 or 3 1/2. Oh! she does not die at WOT just misses really bad. Guess I can run her for a while at WOT shut her down and then check the the plugs. I'll post an update tomorrow after 3 pm. Thanks for the information.

 

[roger3645]

Re: 70 hp, Thought I had it fixed BUT NOT

Okay took her out for a spin today. Ran it with the cowl and air silencer off. All carbs have a good even spray of fuel. #1 plug is the one that is missing, also hear a popping sound I think the #1, coil is arking. Also the #1 plug will get fouled. No way it'll run with the idle screws 3 turns out. I Think my carb setup may be a bit different. On the top of the carb I have only one core plug with a screen on each side. I notice on carb kits the come with core plugs and not screens. Should I update my carbs and replace the screens with plugs? I going to get a new coil and a new set of plugs and gab them at .040 and see if that's the ticket.

 

[roger3645]

Re: 70 hp, Thought I had it fixed BUT NOT

Clanton as far as the SB go. My Tattle tail is at the top of the block and I do have a one piece thermostat seat. I'll check the others.

 

[roger3645]

Re: 70 hp, Thought I had it fixed BUT NOT

Oh! my carbs are the TR model not the SV model maybe that's the difference in idle needle setting.

 

[roger3645]

Re: 70 hp, Thought I had it fixed BUT NOT

Well I gapped the plugs at .040 and replaced the Number#1 coil, and she runs as smooth as silk throughout the entire power range. Thanks for all the help.