The V8 Owners Forum -

Hi. I hope somebody good give some advise. Its a little different because the vehicle with miss fire is a Fonda 16 GTO boat.
i have a miissfire under load. It seems to rev fine under no load but i can only feather the engine to half throttle b4 it starts to miss. I have replaced the plugs,leads, cap,arm and coil.Changed the points and condensor for electronic ignition and set the timing with a light, but this has not curred the fault?
I have zenith carbs, is the fault likely to be caused by a faulty carb? ? I am going to check the tappets for a tight one.
Hopefully somebody can help because it is a right pain dropping thr boat in only to find out its stll missing.
Many thanks .... Nick[/code]

What sort of electronic ignition did you fit? Did you fit the matching coil as well?

Chris.

Hi
Check your diaphrams in the carbs, you probably have a perrished one leading to an unstable mixture, really not an ideal carb for this environment (I presume you take it out on the sea) the SU would be better the Solex/zenith is really a bit delicate for this sort of use.
The other thing to check is the fuel pump, check it is actually delivering enough fuel for wide open throttle, also is the fuel pickup always below the surface of the fuel? is the fuel filter full of water?
Best regards
Mike

Hi
Thanks for your replys. When I brought the boat I put new plugs, leads, cap and points and condensor on before ever using it and the missfire was there 1st launch. I have no idea if it was there prior to me buying the boat.
I then brought the electronic ignition kit and new coil to try and rectify it and it has made no difference, so I'm kind of ruling those two out. I also did the timing with a light at that point.
I could have a dodgy plug or lead although they were all new ??
It's a righ pain because you have to launch it to see if any adjustments made cure it.
If I give it loads of accelerator from stationary it starts to miss straight away. Or I can feather it to half throttle before it starts to miss.
It kind of sounds a bit metallic and just on one bank but defo a missfire.
I'm not used to twin carbs setup. Maybe I should find a 2nd hand manifold and single carb setup ?

Hi
Have you got proper rover V8 cap and rotor arm, pattern ones are not always compatible. You seem fairly convinces it is ignition, yet what you describe, to me, sounds like a fuel supply problem, If not that then I would say coil or condensor, both you have eliminated, so its back to fuel.
I would not recommend a barrel on a boat they yould not like the boncing around and a salt water environment would cause one to rot in double quick time.
I would eliminate the diaphrams and fuel supply side before you change anything else, and probably the fuel filter.
You did empty the fuel tank before putting in new fuel and starting it up didn't you? Just if you had old fuel that had been standing in the tank from last summer and just added a couple of gallons of unleaded before starting up then you probably do have a miss-fire!
Best regards
Mike

Sounds metallic?
Leaking exhaust manifold gasket?

Or I'd check for water in the fuel or fuel filter - presuming a filter king type is fitted.

What type of fuel pump are your running?
Mechanical or electric & if electric which one - perhaps not able to keep up!

Ian

I have a video that the missfire is audible in towards the end of the clip.
Here's a direct link.

http://i151.photobucket.com/albums/s127 ... 768a9c.mp4

Or this is the image code.

I think I would try to borrow a known good set of carbs, flush the fuel system out and give that a whirl.

Chris.

A friend has an SU set up that he said was fine when removed. I have replaced the fuel filters when I put the service parts on. I must confess to not draining the tank as the fuel gauge hardly was registering.
I think a fuel drain and carb strip and investigate is in order.
Thanks for your help guys.

I've been puzzling over this one.

Runs OK until you accelerate and the engine revs rise then it messes about

What about

too much timing and as the engine revs up it adds too much advance so the spark ends up going to the incorrect dizzy post / crossfiring

Probably difficult but start it in the dark and look for the arcing between leads

Or
When it revs up the alternator kicks in and runs too many volts causing the coil to breakdown - is the coil matched to your new Dizzy output? Some are 9v and others 12v

Ian