Throttle issue... stays engaged

[efdog]

I'll try to keep this brief. I have a 2004 Merc 50HP 2 stroke. New to me motor. Took it on it's first run of the year. Shifts smoothly into forward and reverse. Seemed to have no problem getting to WOT and back to idle while underway. I did this 3 or 4 times, then what happened scared the crap out of me! I was heading back toward the ramp, and when I pulled back on the throttle nothing happened...my throttle handle is in the neutral position, but I'm still cruising at about 5000 rpms and 30mph! I moved the throttle back and forth to no avail, and finally was forced to kill the motor.

I was able to easily put her back into neutral, and when I started the engine I guess it was still stuck as rpm's went sky high, and I killed the engine immediately. I took the cowling off to have a look. Everything seems to be moving fine at this point as I move the throttle back and forth. With the engine off, I shift forward and reverse. Nothing seems to be sticking.

Next I start her up again, and am back in normal range. At this point, I'm scared to test WOT again to see if I had just freed something, so I just idled back onto the trailer.

Should I be looking at linkage on the motor or the throttle box itself? ...or both?

Man what a scary moment that was!!

 

[aussieflash]

Re: Throttle issue... stays engaged

Check throttle/shift cable retainers are in place.Check hoses are not obstructing linkage etc.

 

[efdog]

Re: Throttle issue... stays engaged

Check throttle/shift cable retainers are in place.Check hoses are not obstructing linkage etc.

Here's a couple pics...sorry they're dark.

The sheath looks good. Might need a bit of lube. No visible kinks.

The cable retainers to check are in the control box?

 

[aussieflash]

Re: Throttle issue... stays engaged

Cant see in the pic.Barrel retainer at motor and contrl box.Get someone to operate throttle while you watch movement at engine.

 

[efdog]

Re: Throttle issue... stays engaged

Thanks aussie...Everything appears to be moving as it should at the motor. I haven't looked at the control box to see if something may be slipping in there...very stange

Could the carbs have been stuck open? I'm probably not wording that right, but I'm thinking if this isn't a throttle issue, then it's a fuel issue right? I'm running last years gas...Previous owner said he treated the fuel, but who knows. Is there anything I can check visually with the engine either not running, or running on muffs?

 

[aussieflash]

Re: Throttle issue... stays engaged

Stuck carbs wouldnt explain it staying in gear.Check control box.Barrel retainers must be secure at both ends.Something may be loose or broke in box.Did shift handle feel any different?

 

[Big flop]

Re: Throttle issue... stays engaged

The lever that locks the cable
barrels is unlocked?
Move your throttle linkage
by hand
and make sure it's not
hanging up on anything.

 

[efdog]

Re: Throttle issue... stays engaged

Stuck carbs wouldnt explain it staying in gear.Check control box.Barrel retainers must be secure at both ends.Something may be loose or broke in box.Did shift handle feel any different?

That's true, although I can't be sure I backed off the throttle completely while I was underway as it all happened pretty quick...I do know that after killing the engine, I played with the throttle a bit moving it back and forth, and when I went to restart, i was in neutral and the rpm's soared immediately to 5000+. The shift handle still had normal resistance.

I'll have a look at the control box itself tonight to see if something broke off or is loose in there.

The lever that locks the cable
barrels is unlocked?
Move your throttle linkage
by hand
and make sure it's not
hanging up on anything.

I unlocked the lever when I was checking it all out, just to see if something was in there. Yes the throttle linkage seems to move freely and smooth as it should

Thanks guys. Hopefully I'll find something in the ctrl box.

 

[Georgesalmon]

Re: Throttle issue... stays engaged

I had a similiar problem once. It was the plastic barrel at the end of the cable that hold it in place. It was broken in half in the remote control (very hard to see). Sometimes the outer sheath of the cable would move instead of the inner cable. It was intermittent and the reason I have so little hair today.

 

[efdog]

Re: Throttle issue... stays engaged

I had a similiar problem once. It was the plastic barrel at the end of the cable that hold it in place. It was broken in half in the remote control (very hard to see). Sometimes the outer sheath of the cable would move instead of the inner cable. It was intermittent and the reason I have so little hair today.

Thanks George, I'll make sure to look closely. Yup, nothing worse then cruising along at WOT with your handle at noon. For a second, I was actually thinking "oh crap, I'm done!", then of course realized I could just kill the engine.

Kind of reminded me of this video...http://www.youtube.com/watch?v=ZSxK9bhMNj8

 

[Georgesalmon]

Re: Throttle issue... stays engaged

Off the subject but; many years ago MirroCraft was producing Sierra glass run-a-bouts (not made for quite a few years). I was plant manager at the time. We had a guy buy a 18' sterndrive from a local dealer on Friday. He took it out of Green Bay WI and hit a breakwater WOT I'm sure close to 60mph. Tore the lower unit up big time and he went through the glass STBD side windshield, took it off the boat frame and all. The hull and transom actually held up pretty well. No holes just a bunch of deep scratches (of course we couldn't see the "hidden" damage). Anyway, he showed up on Monday morning (happened on Sunday) with the boat on the trailer and needed a repair estimate for the insurance company. He was covered in badages, cast on one arm and the other wrist, and on crutches. I think we told him no way we would fix it because of the liability of what we couldn't see. The only estimate was for a whole new boat minus the trailer. Never heard how it ended but he was lucky to be alive. Imagine, lol, The Monday Morning after. Guy was a hardcore boater. Oh yeah, and I still rember the boat was red.

 

[efdog]

Re: Throttle issue... stays engaged

Off the subject but; many years ago MirroCraft was producing Sierra glass run-a-bouts (not made for quite a few years). I was plant manager at the time. We had a guy buy a 18' sterndrive from a local dealer on Friday. He took it out of Green Bay WI and hit a breakwater WOT I'm sure close to 60mph. Tore the lower unit up big time and he went through the glass STBD side windshield, took it off the boat frame and all. The hull and transom actually held up pretty well. No holes just a bunch of deep scratches (of course we couldn't see the "hidden" damage). Anyway, he showed up on Monday morning (happened on Sunday) with the boat on the trailer and needed a repair estimate for the insurance company. He was covered in badages, cast on one arm and the other wrist, and on crutches. I think we told him no way we would fix it because of the liability of what we couldn't see. The only estimate was for a whole new boat minus the trailer. Never heard how it ended but he was lucky to be alive. Imagine, lol, The Monday Morning after. Guy was a hardcore boater. Oh yeah, and I still rember the boat was red.

what a trooper! Did he ever mention why he hit the breakwater? Night fishing or something and not familiar with the waters?

Well I wont be doing 60mph with my 50hp, but still don't really want to test out hitting something at 30mph.

 

[Georgesalmon]

Re: Throttle issue... stays engaged

It was a bright, sunny, warm, Sunday afternoon. No, he never said but if I had to guess,,,,, I would guess that "barley pop" may have been involved.

 

[efdog]

Re: Throttle issue... stays engaged

Good news and bad news...The good news is that the control box is functioning as it should. Nothing appears to be out of place or broken, and everything is well lubed and moving freely.

here's a video...kind of...I had to hold my phone with one hand and operate the control with the other. Not easy from outside of the boat.

I'm stumped. I guess my next step will be to take the boat out and try and diagnose on the water...if it even happens again. I'm not really too keen on that idea though.

 

[Georgesalmon]

Re: Throttle issue... stays engaged

Good luck and you already know to be careful

 

[efdog]

Re: Throttle issue... stays engaged

Well, I have no idea if this could be related to my issue or not, but today I was poking around in the bilge and found the ground to the engine just hanging there!!! I know with pretty much anything electrical, that if there's a ground problem, then strange things can happen. The ground is now on the battery where it should be. Anyone know what kind of issues can arise from not having the engine block grounded to the battery? Should the ignition even work without it grounded?

 

[CharlieB]

Re: Throttle issue... stays engaged

The ignition is self-generating and is a simple 'Ground-to-Kill', the battery is only on board to make starting easier.

It 'could' be possible that the battery charging circuit created an arc thru the control cables as the ground cable came loose/off, possibly spot-welding the cable in the WOT position. You continued movement of the control after killing the motor may have broken the cable loose again.

You may have been extremely lucky, your quick thinking and killing the motor averted a possible tragedy.

 

[efdog]

Re: Throttle issue... stays engaged

It 'could' be possible that the battery charging circuit created an arc thru the control cables as the ground cable came loose/off, possibly spot-welding the cable in the WOT position. You continued movement of the control after killing the motor may have broken the cable loose again.

Thanks Charlie...just to clarify though, my ground cable did not come loose from the engine, but actually was never attached to the battery itself... so all I had was a ground cable coming out of the engine and into the bilge just dangling there. Had I not been looking around in the bilge I would never have noticed this cable not being attached as it did not enter the battery compartment at all.
I had been running the engine without it grounded.

 

[efdog]

Re: Throttle issue... stays engaged

Just had it back out, and low and behold the problem did NOT fix itself...whatta ya know.
So I'm really stumped on how I can troubleshoot this. Happened almost exactly the same as the 1st time except I had plenty of water and was prepared. I started out by cruising around at various rpm's for about 5 minutes or so. Then I stayed at about a constant 3500 or so (just on plane), I slowly started to pull off the throttle, but rpm's did not change...I pulled it right back into neutral, and as soon as it clicked into neutral of course the rpms shot right up, and I killed the engine quickly. Without touching the throttle, I took the cowling off and took this picture...

I was able to move the throttle back and forth, and again, everything seems to be moving as it should. Nothing felt different when pulling off the throttle.

It started back up in normal rpms, and I was able to cruise back onto the trailer without any issues.

So what I know is that this happens randomly, and not at will. The engine is getting fuel when I'm not telling it to.

Where do I go from here?? Very frustrated...any help is really appreciated.

 

[CharlieB]

Re: Throttle issue... stays engaged

Take a very hard look at the throttle linkage on the carbs, I'd be opening and closing the carb linkage at the point the roller pushes the carbs open to feel for even the slightest roughness, sticking or binding. If the linkage is not sync'd correctly and even one carb is being pushed past a normal WOT position the butterfly/throttle shaft can bid in that carb, hanging all the carbs open until a strong enough jolt, jar, vibration causes the stuck carb to release.

The throttle/timing lever may be returning but if the carb linkages sticks at all, the carbs will stay open even tho the throttle control and timing are returned to the idle position. The motor will keep on going til the carbs close or you turn off the ignition.