Yamaha 703 throttle problem

Dan Gurney · 27 August 2013, 22:58

Sorry for the flurry of posts but having used the boat more in the last fortnight than in the preceding 9 months I have a bunch on niggly little things I'd like to get sorted (such as engine height) over the winter.

I have noticed that the throttle seems to slip slightly and the engine gradually loses revs. I can open the throttle again and the revs pic up fine. It also seems to be particularly pronounced in heavier weather, if there is any sort of impact from waves. It doesn't seem to do it at all in flat water. I cannot see the lever actually moving which suggests it's something inside the box. I have tried tightening the friction adjuster but this seems to have little or no effect. There also seems to be a variable amount of 'play' in the thottle: sometimes you need to move the level 10 - 15 degrees in the desired direction before anything hapens to the revs, other times it works straight away.

These observations are all from using the boat and not based on methodical trouble shooting but I thought I'd see if anyone has had similar issues. From a search of 703 issues it seems quite a few people have had them apart in the past.

spartacus · 28 August 2013, 06:33

Assuming its Teleflex 33C throttle and gear cables, are they old, tight bend on route to engine, any damage, etc? Disconnect at throttle and engine end and feel for friction and play while moving. Should be pretty fluid. If clear, then connect to throttle end again and use adjustment lock screws at engine end to remove any play (in neutral), and that you have full WOT (wide-open-throttle). Test, etc.

9D280 · 28 August 2013, 08:55

You might be surprised at how far the lever can move and not be "noticable". The engine RPM drop is more pronounced at higher RPM. The engine will have a return spring that will drag the throttle back to ilde - that is likely what is doing this.

There is (or should be) a friction screw at the front of the 703. Give it a clockwise turn (& try it before you go out - you can lock it almost solid if you turn it too far!) & see if that cures it.

Dan Gurney · 28 August 2013, 09:06

Quote:

Originally Posted by Clamchowder

I have tried tightening the friction adjuster but this seems to have little or no effect.

plus 5 characters

jyasaki · 29 August 2013, 15:26

On my Yam control, I had to really crank the friction adjustment to get the throttle to nearly static. It is still prone to rolling off slightly, but I'm afraid to try and tighten the thing any more than I have. Just something to live with for now (not that a hand on the throttle is a bad thing anyway.)

jky

9D280 · 29 August 2013, 15:50

Quote:

Originally Posted by Clamchowder

plus 5 characters

D'oh. That'll teach me to skim read stuff at work.......

davej · 29 August 2013, 20:24

I replaced the 703 and cables recently on our dive boat, simply because it was wearing out and had developed slop, not only in the cables but the control box. This dated to 1994 and had worked well for many years but the time had come and replacing both has worked a treat. When we took the 703 apart we came to the conclusion that all the various sliders, cams and wheels etc had all worn a little and gave it this slop. A set of cables and a box from BHG marine were exactly £300.

We had tried all sorts but ours had worn wasn't just loose friction etc.

Dave