75hp Johnson Stinger low Compression PLEASE HELP

[camohunter]

I've got a 1980 75hp Johnson Stinger 20" club foot on a 1652 aluminum boat. I've ran this motor a good bit in the last year and it always runs really strong and fast, but will not idle very well. The carbs are clean and have new main jets installed (did not help idle problem). It spits and sputters a mist back out of the top carb and cuts off under low rmps.

I bought a compression tester and the compression checked out weak yesterday @ 79,80, & 85 lbs. Is this low compression possible on a motor that runs strong? Do you think I got a bad compression tester. I tested the motor warm with all the plugs out and at wide open throttle.

Thanks in advance for any advice.

Justin

[captbone]

Check and replace the reeds. The mist out the top carb is hint something maybe going on with reeds.

[camohunter]

Can the reed valves affect the compression readings?

[captbone]

No but your compression readings are all with 10% of each other. I would not be overly concerned. Replace the reeds and retest your engine. I think they are your issue and will fix idle and run quality.

Just my 2 cents.

[25XS]

Sounds to me like you need a THOROUGH carb cleaning, followed by a procedure in your service manual called "Sync & Link" where you synchronize (properly per the book) the carb butterfly opening to the timing advance mechanism... I have done lots of them and they make a sick engine run like new.

You also may have lost the clear, outer sleeve off the carb advance cam roller ("Roller & Sleeve ***'y" in the parts list) so the timing is advancing ahead of the throttle plates. That would cause the "Lean Spit" backfire through the carbs.

I'm in Georgia, too (Buford / Lake Lanier) Where are you located?

Tom

[camohunter]

Sounds to me like you need a THOROUGH carb cleaning, followed by a procedure in your service manual called "Sync & Link" where you synchronize (properly per the book) the carb butterfly opening to the timing advance mechanism... I have done lots of them and they make a sick engine run like new.

You also may have lost the clear, outer sleeve off the carb advance cam roller ("Roller & Sleeve ***'y" in the parts list) so the timing is advancing ahead of the throttle plates. That would cause the "Lean Spit" backfire through the carbs.

I'm in Georgia, too (Buford / Lake Lanier) Where are you located?

Tom

I live in Wayne County on the Altamaha River.

I've had the carbs off and adjusted the linkages and stuff when I installed the tiller handle, so that could be the problem. I really don't think it's trash in the carbs. I feel like I'm pretty good at cleaning the carbs. I would take it to the boat mechanic here, but I don't have a lot of confidence in them. Do you think my compression is too low? I have read that these stinger motors should be around 150psi.

Thanks for the help! I'll research the Sync and Link