Throttle control woes - Yanmar 3GM30F

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dunedin

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Having had no problems with this previously, having a range of fun and games with the throttle controls these past few weeks

The cable failed in August - and was replaced by the yard engineer at Crinan. Cable was very slightly longer than the one removed (5.5m vs 5.25m) but otherwise seemed to be working fine.

However having been little used in the following weeks, am now having problems with the engine revs not dropping back when the throttle is moved back to neutral - stays 1,500+ revs unless manually pulled back at the engine end.
Stripped morse lever and no visible problems. Ditto at the engine end. Cable clearly new.

Jury rigged a bungy cord to pull throttle back to get into berth - which works to reduce revs as a temporary measure, but this doesn't allow use above 1/2 throttle and a bit of a bodge.

Can anybody explain what should return the throttle to low revs ? Is there a spring mechanism at the engine end or is it just the Morese lever pushing back the cable?
Any ideas ?
 
there is a return spring at the engine end.

our combined throttle/gear lever jammed this summer, have been selecting forward/reverse with the (disconnected) bike cable since, and left throttle on the control. its a fairly strong return spring, now that the throttle control lever is not sticky with 39 years of alum corrosion i have to use a bingy (its not just you!) to keep the revs up. (3gm30f also)

reason for delay in replacing control unit is not sure what to replace it with ie like for like that cunningly gets the mainsheet wrapped around it or hide it inside a cockpit locker

ps any sharp bends in the new control cable?
 
bikedaft said:
there is a return spring at the engine end.
Click to expand...

Thanks very much for the prompt reply.
Is the spring clearly visible - presumably somewhere on the throttle lever (not on the boat now but didn't notice it - perhaps could have come off)

bikedaft said:
ps any sharp bends in the new control cable?
Click to expand...

Unfortunately the route it comes has a few fairly tight spots - the fitter was cursing the boat designer, but it had worked fine for the last 10 years with this route.
 
We had a very similar problem this season - engine just seemed to rev higher than usual on "tickover". Found the problem at the Morse control end. The cable sheath passes through two holes, at least one of which should have had a circlip to prevent the sheath moving. For some reason, the circlip(s?) were missing - maybe had corroded & broken - but whatever the reason, the cable sheath could move freely. I pulled the sheath back to its correct position and fixed it in place using a couple of thin SS bolts/nuts which located in the slot the circlip should have sat in. Problem solved.

Not saying you have the same problem but worth a look.

Hope this helps.
 
the spring is internal to the engine gubbins. the easy way to tell is to detach the bike cable type thing at the engine end, its a small split pin, don't drop a washer in the bilges like i did, tho its worked fine for a while since... then it returns to idle, and you need to push the lever pretty hard against the internal spring to rev it.
 
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