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Old 05 June 2009, 14:57   #1
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Country: UK - Scotland
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Tohatsu 50d2 Timing Problems

Last year I carried out a tune up following the Clymer Workshop Manual and afterwards the engine would rev high at tick over and had lost some of its top end speed. After adjusting the timing and throttle link rods I managed to regain some top end speed but the tick over is still high and idle screw makes no difference. The timing link is set at 98mm and throttle link is 115mm.

I tried again today to set up the timing but there seams to be three flat surfaces one left one middle where gasket and head meet and the 3rd on the right, the manual states to align the flat surface of the crankcase mating surfaces with the calibration marks on the set rings. Any one know which one it is?
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Old 08 June 2009, 13:09   #2
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ya, first take that clymer manual, run down the dock as fast as you can with it, stop short at the end and launch it.
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Old 08 June 2009, 15:43   #3
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Yeah funny enough your not the first person to tell me to lauch the Clymer Manual.

Managed to get hold of the Tohatsu Service Manual, its a good bit better.

Managed to sort the high rev problem but now lost power, seamed to be that only 2 of the 3 carbs were working. I gave a quick clean of the jets a couple of days ago, but I stripped the carbs fully today and gave them a proper clean to find that the fast jet on one of the carbs had been clogged up.

Whilst reinstalling the carbs I found the timing mark which is situated higher up than where I was looking. So managed to set up the timing as well, hoping to get the boat on the water near the end of the week to see if it has sorted out the running problems.
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Old 09 June 2009, 03:48   #4
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Quote:
Originally Posted by bobbyjoeufb View Post
Yeah funny enough your not the first person to tell me to lauch the Clymer Manual.

Managed to get hold of the Tohatsu Service Manual, its a good bit better.

Managed to sort the high rev problem but now lost power, seamed to be that only 2 of the 3 carbs were working. I gave a quick clean of the jets a couple of days ago, but I stripped the carbs fully today and gave them a proper clean to find that the fast jet on one of the carbs had been clogged up.

Whilst reinstalling the carbs I found the timing mark which is situated higher up than where I was looking. So managed to set up the timing as well, hoping to get the boat on the water near the end of the week to see if it has sorted out the running problems.
I have seen a sticking reed cause that symptom, worth having a look with the carbs off. The other thing is the balancing of the carbs would also cause it. Was the engine sitting doing nothing for a while before you tried tuning it ?

The big worry is oil feed; if one of the carbs has been running lean,it's been under oiling the related cylinder.

Your blocked jet could be the obvious cause , if it were me I'd take an airline to all the jets and balance each carb again, just to make sure.

best of luck.
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Old 09 June 2009, 04:04   #5
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Thanks for that.

The engine had been sitting for about 8 months, but I did take the carbs off and gave them a quick clean over with carb cleaner and removed the fast jets and checked they were clean. The blockage happened after it had all been put back together.

I have fully stripped the carbs; cleaned and used an air hose to ensure all passage ways and jets are clear. So with any luck should be sorted, no doubt will have to adjust the carb mixture and timing when its on the water.
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Old 09 June 2009, 22:26   #6
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sinc and link the carbs before you start it up. back the idle screw out till it does not touch the carb arm, loosen the other two carbs at the link, re-tighten them,
check that all carb plates are closed, then put some idle speed back in to it.

it will never run right unless you link and sinc them. carefull, some link screws are reverse thred.
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Old 11 June 2009, 15:22   #7
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Quote:
Originally Posted by fast fred View Post
sinc and link the carbs before you start it up. back the idle screw out till it does not touch the carb arm, loosen the other two carbs at the link, re-tighten them,
check that all carb plates are closed, then put some idle speed back in to it.

it will never run right unless you link and sinc them. carefull, some link screws are reverse thred.
Thanks I have followed the manual and syched the carbs up, however I noted that the bottom two carbs were not opening fully. Tired the Throttle Level Screws but still not working so I have adjusted the Throttle Link Rod which the manual sets at 90mm although its now set about 95mm. Will hopefully get to try it out on the water some time next week.
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Old 03 July 2009, 11:24   #8
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Taking a while to get the boat back on the water thanks to a back injury at work.

Zapcat is running perfect!

Hopefully heading up West next weekend, so will take the GPS out and see how fast its going.
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