Backfiring engine losing power

lewglo · Post by **lewglo** » Mon Jul 16, 2012 9:35 am

We are new to this site - but have a 28' Trojan with flybridge. We have 318 Chrysler engines and have had trouble with both. Two mechanics have worked on them and neither seems to know what the problem is. Had a compression test which was good. Trouble with starboard engine we hoped has been resolved although not able to test it yet - mechanic replaced several parts and put a new electronic ignition in. While he did this he suggested we replace the port one as well, so as not to have any future trouble. This was after having to replace the starter on the port engine. Unfortunately this engine now backfires and loses power as soon as you put it under load. It will idle all day at the dock and will motor at about 7 knots on way out of harbour. As soon as it heats up for a few minutes it backfires and there is no power. Anybody had this problem, we would certainly love to hear from you - we are really at our wits end with this - this is the second year in a row we have not been able to use the boat - and we have spent a tonne of money on trying to resolve the problem. Until we can get the port engine problem rectified we cannot test to see if the starboard engine has actually been fixed. Thanks for your help....

sluggo · Post by **sluggo** » Mon Jul 16, 2012 11:11 am

but when I went through backfire issues it was always water in the fuel.
so I would check my water/fuel seperaters. On mine there are 2, a 'big one' that is from the gas tank into the engine, and a 'liitle' one that is in the carbourator. I did change the filters in my big one several times, to really no advail. I found that not all the parts where in the filter system, and when I replaced them, everything seemed to work fine. if it were me I'd start there.

Torcan · Post by **Torcan** » Mon Jul 16, 2012 12:52 pm

Many things could be wrong

some that come to mind are:
Ignition timing incorrect
Damaged valve springs or sticking valves
vacuum leak
intake air (vacuum)leak
water in fuel
too rich?

BarryL · Post by **BarryL** » Mon Jul 16, 2012 3:03 pm

Spark plug wires out of order?

kallen · Post by **kallen** » Mon Jul 16, 2012 5:19 pm

Remember the K.I.S.S it rule.
1- firing order
2- timing & advance total
3-spark plugs & wires ( proper routing of wires)
4-Timing chain play ( no more that 8 degrees)
5-ballast resistor voltage
6- coil voltage
7- carb float level
8- fuel pump pressure test
9- fuel filters
10- ignition control box
We are assuming that good parts were installed by your mechanics & that the distributor is correct.

alexander38 · Post by **alexander38** » Mon Jul 16, 2012 6:33 pm

+1 on Kallen

k9th · Post by **k9th** » Mon Jul 16, 2012 6:37 pm

From my little bit of knowledge, it sounds like the answers already given pretty well cover it.

Welcome to the forum.

prowlersfish · Post by **prowlersfish** » Mon Jul 16, 2012 7:37 pm

Did It do it before it was worked on ? If not start there ,

Jfreeman1412 · Post by **Jfreeman1412** » Mon Jul 16, 2012 8:10 pm

Water in Fuel

Coil may be bad.....It will act good until it heats up and will go bad.

Try here....http://www.marineengine.com/boat-forum/ ... rive-Forum

Lots of experts that are willing to help.

Big D · Post by **Big D** » Mon Jul 16, 2012 10:12 pm

Jfreeman1412, did you get straightened out with your distributor - got the answer you were looking for on that site?

Jfreeman1412 · Post by **Jfreeman1412** » Mon Jul 16, 2012 11:41 pm

I have got a ton of advice and knowledge....I will be heading out to the boat this weekend and hopefully will have some answers for everyone. Still need to find out if my distributor is advancing, but will find out this weekend.

tunatamer · Post by **tunatamer** » Tue Jul 17, 2012 9:44 pm

I would. Check the distributed. The old ones have system where the more the elms increase the mechanism turns and thus advances the timing. If this isn't turning as the rpm increased the timing will be thrown off thus creating a backfire situation. I'm actually a marine tech. And have come across this on.older vessels with the original distribiter. Hope this helps. Josh

Jfreeman1412 · Post by **Jfreeman1412** » Tue Jul 17, 2012 9:52 pm

Hey Josh
When you replace the original distributor, do you just set the base timing or do you set the advance? And a shot in the dark.....Do you have the advance curve for the 318 marine engines?

What brand of distributor do you replace them with?

g36 · Post by **g36** » Wed Jul 18, 2012 8:53 am

although i am not capt josh
i replaced both of mine on my 78f32 318s with these. summit had a good price then you might look around and find them cheaper. both engine rotations on my 78 318's used the same distributor . the rotation is the same for the distributors on my engines. and as i recall i set at the 5 degree mark .

http://www.summitracing.com/parts/MAA-YLM579AV/

jefflaw35 · Post by **jefflaw35** » Wed Jul 18, 2012 8:07 pm

nice add G36, a bit pricey but im going to look araound like you said. I still need a new one. Thanks for the input!!

Trojan Boat Forum

Backfiring engine losing power

Backfiring engine losing power

I dont know much