back fire

[diversion]

hi i have trojan f26 318 engine it back fires at around 2800 rpms sometime can't get to full rpm i change gas filters plug & wires what could it be

[woodboat]

On a Chrysler marine my first thought is the Ballast resistor. They are cheap and easy to replace. I thought I had a Carb issue on my last boat, A marinette with a 360 but it was only the resistor. Short of that I would be thinking coil and distributor. My current boat with a 350 chevy was backfiring. Replaced the distributor with a Mallory unilite, all is well now.

[Corpus Skipper]

I concur with woodie. You can eliminate a lot of headaches with electronic ignition. I converted my 350s with a kit from Pertronics, replaces the points, uses same distributor. About $70 per engine, available from Summit Racing (www.summitracing.com). They're worth their weight in gold! :D Also got easier starting and reduced fuel consumption (3 gph per with new carbs as well)

[Corpus Skipper]

http://store.summitracing.com/default.asp?target=edepartment.asp&N=120+4294925143&x=17&y=8
Here's the page.

[gonzo]

2800 RPM is about when the secondary springs start stretching. If your distributor shaft/bushing is worn out or the springs are weak it will overadvance.

[trouty]

the distributor cap, and make sure there isn't an blackened carbon 'arc' created between two adjacent HT outlet poles on the inside of the cap.

If it gets wet under the cap and any salt deposits there - the spark can track across to an adjacent spark plug wire lead inside the dizzy cap - thus firing a cylinder before the exhaust valve is closed - (or when the inlet valve is still open - meaning a backfire thru the carby!).

Good luck.

[Frans X L]

backfiring is usually a sign of retarded ignition timing.