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63 40hp RKL-25D stalls out when quickly pulling back throttle

vandenburgh

Contributing Member
Engine starts fine, and throttles up fine, but when pulling back quickly on throttle from running at 3500 rpms or so, engine stalls out. If I pull it back slowly instead, it seems to be ok. Any suggestions as to what may be the problem causing it to stall out on rapid deceleration?

I am currently running it in a test tank, but had this issue last time it was in the water as well.
 
Good to hear from you kimcrwbr1...
On low speed jet...
I adjusted the low speed jet best I could in my test tank when I went about getting it fired up the other day (needle was loose as I suspect I didn't tighten the packing nut tight enough couple years back, so I guess and it must have vibrated loose. I also dressed the needle by chucking it lightly in drill and sanding against 200 grit, then 1500 grit - did this to get groove out from another mistake I made couple years ago - probably damaged needle as I didn't heed advice last time to 'lightly seat'. As I couldn't run at WOT in test tank, just maybe 3/4 and only for short burst, probably need to dial it in on the water.

on link and synch.....I will check old thread, as I know we covered this, maybe I didn't get it right last time. Will check and report back.

on slightly different topic...how steady should the fuel flow be through filter bowl at idle?....after pressurizing line and filling filter bowl, starting engine and idling, the fuel seems to empty from bowl, then refill bowl, then empty, refill, repeat. Is this normal? (I guess I would have expected fuel level to remain a little more constant in bowl as it flows through, vs almost emptying out before more fuel squirts in, Just checking to see if I may be developing fuel pump issue or fuel line clog).
 
Any two stroke outboard... yanking the throttle back from a high rpm to a flat idle would most likely result in having the engine fall on its face. They're just not designed to respond smoothly to that action.

The 1963 40hp Evinrude/Johnson model incorporates a brass fixed high speed jet, located horizontally in the bottom center portion of the float chamber, way in back of the float chamber drain screw. Making sure that the ID of that jet is percectly clean is all that's needed to insure that the fuel flow at high speed is set properly.

Set the adjustable slow speed needle valve as follows.

(Carburetor Adjustment - Single S/S Adjustable Needle Valve)
(J. Reeves)

Initial setting is: Slow speed = seat gently, then open 1-1/2 turns.

Start engine and set the rpms to where it just stays running. In segments of 1/8 turns, start to turn the S/S needle valve in. Wait a few seconds for the engine to respond. As you turn the valve in, the rpms will increase. Lower the rpms again to where the engine will just stay running.

Eventually you'll hit the point where the engine wants to die out or it will spit back (sounds like a mild backfire). At that point, back out the valve 1/4 turn. Within that 1/4 turn, you'll find the smoothest slow speed setting.

When you have finished the above adjustment, you will have no reason to move them again unless the carburetor fouls/gums up from sitting, in which case you would be required to remove, clean, and rebuild the carburetor anyway.

Thousands of parts in my remaining stock. Not able to list them all. Let me know what you need and I'll look it up for you. Visit my eBay auction at:

http://shop.ebay.com/Joe_OMC32/m.html?_dmd=1&_ipg=50&_sop=12&_rdc=1
 
Thanks for the quick reply. On the cutoff switch suggestion, what are the conditions that are supposed to trigger cutoff switch? Is it triggered by over revving? just curious as to how it works and what conditions are supposed to trigger the switch and how my situation might be triggering it to disconnect when it shouldn't. I will try bypassing switch as suggested once I confirm link & synch not issue. Thanks
 
Update: I finally got the boat on the water today at the lake cottage so I could move beyond test barrel. Happy that engine started and idled fine, but downhill from there. Engine wouldn't hit full rpms. Didn't get too far trouble shooting as starter failed (hopefully just dead battery, but not too confident, but battery is on charger overnight). That said, before starter issue I checked and adjusted link and synch and believe that part is ok..this is how synch is working...butterfly just begins to open as marks on cam passes pointer on intake manifold as throttle is applied and continues to open as follower tracks cam as throttle is increased. when near end of cam, and throttle is pushed to WOT, butterfly fully opens....hopefully that part is right. After adjustment, tried engine again, and same issue.

So starts fine and starts out fine as throttle applied, but never reaches full power...it never fully planes boat off and it did so when last running season before last (wasn't in water last season), like it isn't getting full throttle. As a lark, I disconnected bottom cylinder to see if boat operated same way as when both were connected, and it showed same behavior whether bottom spark plug wire attached or not, so I am thinking bottom cylinder not firing at all but not sure and maybe it is something else, but thought I would mention. That is as far as I got, before my starter began acting up and not engaging (solenoid clicks, starter groans and spins a bit, but does not fully spin up)

Assuming I can get starter working (battery now on charger), what is recommended steps to trouble shoot engine not reaching full power? For now, I would like to assume compression ok as I don't have my tester with me and here through the coming weekend...and boat ran ok at WOT, maybe 20mph or so, last time on water couple seasons back at end of season).

I assume i should check status of spark on bottom cylinder as my next step. Any suggestions for next steps would be welcome as I contemplate situation while battery charging overnight (keeping fingers crossed starter hasn't gone bad!)
 
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