TOPIC: Mercury 500 Throttle adjustment

I have a 67 mercury 500 that I just replaced the impeller on. We have everything back together and are able to start the engine. We have the bottom end in a tub of water and I'm getting some water spitting out the back ports and some dripping at the pee hole. When we put it in gear the prop engages but as we add more throttle it only appears to go one speed and doesn't go faster unless we physically turn the distributor. The control box has a black lever that says lift for cold starts and the motor will only run if this lever is halfway or all the way engaged. Is there something we are overlooking as far as the throttle linkage is concerned? Hoping to get this to the lake soon and we are almost there but keep running into little snags. Any help or suggestions are appreciated.

Rick
67 HydroSwift w/ Mercury 500 Thunderbolt

upon futher investigation it almost appears as if the throttle is backwards. When moving the accelerator forward the prop appears to move correctly pushing water away but I only have one speed no matter how far I push the handle forward. When engaging reverse it slowly opens up and turns the distributor and the carb linkage. Where did we go wrong? Could we be off on the shift shaft on the lower unit? (we did have some trouble getting it lined up correctly so the shift lever would go back and forth and the prop would spin freely in neutral).

Confused in ID at the moment....

Rick
67 HydroSwift w/ Mercury 500 Thunderbolt

you might have a box for a 20hp they were backwards.or check and see if you have the cables on wrong but i would think it is the box.

Update:

It looks like the warm up lever allows the throttle to fully engage when it is off. However, when we try to slowly back off the warm up lever the motor will die. It will only run with the warm up lever 3/4 or all the way engaged. Once we hit about half way the motor starts to sputter and die. So now the question is we have is about the warm up lever. How long does it need to be engaged before the motor is warmed up? Why does the motor die when trying to slowly disengage the warm up lever? I think once we get that figured out we can adjust the carbs properly and head to the lake for a trial run.

Sorry for all the out loud thinking, just trying to get this out board figured out.

Rick

Rick, the warm up lever should only be needed for a few minutes, if everything is set as it should be. Did you have the timing belt off, or the plug wires, or the throttle cables? Just wondering if it was running well prior to your impeller replacement, or if you have some tuning to do.

Thanks Mark for the reply I appreciate the help. We replaced the impeller and cleaned the carbs. We had the carbs off and did our best to put them back on just as they came off. My Brother in law said they got it running but didn't run it long because of lack of water out the pee hole so not sure if it was running as it should before we started. We've run it some more and it idles slightly rough but smoothes out when manually giving it some throttle. We can still only get the warm up lever backed off to half way (from all the way on) before it studders and dies. Not sure what is wrong at this point but I think we are close if we can figure out the warm up cable and get it off so we can accelerate instead of just idle. Any ideas would be appreciated as others are starting to get impatient and we're hoping to make it to the lake....

Rick

With the main throttle/shift lever in neutral and the fast idle lever down, is the distributor resting against the idle stop screw? There are stop screws for WOT and idle. The distributor rotates without opening throttle to carbs for the first portion of increase, you may need to adjust the idle stop in a little and try that. (It also does this in reversing, just not as much.) Is there a lot of play in your throttle cable? They (the cables) really should be adjusted per the manual, let me see if I can find a copy of the "link and sinc" procedure.

With the throttle in nuetral and the warm up level down (off) the distributor is resting against the stop idle screw. With the engine off we moved the warm up lever back and forth and it when it is engaged halfway the distributor is about a 1/4 inch away from the stop screw. As the distributor turns closer to the stop screw it sputters and dies. The cables don't seem to have a lot of play but info on how to adjust them would be handy just in case.

Rick

Check your email inbox Rick.

Mark, I really appreciate your help. I checked my email but don't have anything new. You can email direct at rhedelius at hotmail dot com.

Engine is currently idling with an occasional slight surge but still have the warm up lever just above half.

Rick

I wonder if maybe one of the carburetors float needle is stuck shut?
Sounds like maybe she isn't running on all (4).
What are the idle jets set at?
Try squirting fuel mix into each carburetor with a pump bottle (like an empty 409 bottle) and see if the beast perks up at all.

As you probably already know - the warm up throttle lever needs to be completely down (slow) before shifting into either Forward or Reverse and it needs to stay down after that. If it is creeping up on you it needs to be repaired before the inside of the control box gets damaged.
Thom

Thom/Mark,

Thanks for you help and suggestions. Haven't had time to get to it today with family stuff going on, but hopefully tomorrow we'll get another stab at it for some more troubleshooting. I'm anxious to get this in the water for a test drive....stay tuned..

Rick

dave bernard wrote:

you might have a box for a 20hp they were backwards.or check and see if you have the cables on wrong but i would think it is the box.

Only gearshift is backwards on the 20hp & down controllers. No difference internally on the throttle side. We have tons of 'em here in the UK!

ok, after some fiddling around it looks like the bottom 2 cylinders (3&4) are not firing. We pulled the wires while running and there is spark but the engine doesn't die when completely removing the wire like it does on the top 2 cylinders. We put brand new plugs in but same thing. Where do we go from here? I having a feeling if we can get those two running the warm up lever will come off like it's supposed to and we can make a trial run in the water. Any ideas?
We're scratching our heads at this point.

Rick

Compression test results:

Cyl 1 = 115
Cyl 2 = 110
Cyl 3 = 110
Cyl 4 = 115

I'm not an expert but that seems ok to me.

Rick

Rick, what did the spark plugs look like from 3 and 4? Wet with fuel, or dry?

They were a little wet because we were running it but not saturated.

Rick