3.0 mercruise wont start

new 3.0 mercruiser installed i have the ddis installed when i turn engine over it sounds like it is going to start but does not also backfires thru the carb

i thought it was a new carb?

 

Sounds like the ignition timing is not set right.

 

that is what i was thinking but i have the diss system on mine i have looked up the setup and you really cant srew it up from what i am reading the #1 piston does not even have to be to the top

 

cant get my 3.0 mercruiser to start. wont run. but fires up. backfires

I Bought my boat this summer used it is a 1987 searay deville, with a 3.0 mercruiser. and alpha one outdrive ..I drove it all this summer with no problems at all. Infact it always started 1st time.. this year I replaced the plugs . all new bellows, and all fluids were changed. Ok heres what happened. about a week ago I noticed 1 side of the exhaust bellows came off. i called the marina and spoke to a mechanic he stated that it would be ok to ride it that day as long as I didnt let off the throttle really fast at high speeds. not sure what he meant by that. but I did what he said. anyways when i was driving it I noticed it wasnt driving near as fast as it normally did.(maybe because of the exhaust bellows ?)it felt like i was driving 5 to 8 mph instead of 40mph. it just wouldnt plane out. infact it felt like it was dragging a house. then the motor stalled. and every since it wont start. It starts for like 1 to 2 seconds. it fires everytime. cant figure it out. it gets spark to all 4 plugs, its getting fuel in the carb. I am lost. if you hold the key over in start position its like running. and when you give it gas with key turned over it even revs up,,and if you do it for about 6 seconds sometime it backfires...But like I said you have to hold the key in start position. as soon as you let off on the key it stalls out.. my neighbor inspected it and says it seems like the ignition in the dash is bad. My brother also inspected it and says it sounds like the timing. he checked the points and everything.. both my neighbor and brother are good car mechanics. but dont know to much about boats.any real boat mechanics here can tell me what they think?

 

Your problem is the ballast resistor circuit.

When you crank the engine the ign system is fed by another circuit. When you release the ign switch another sytem takes over,-- this bit is not working.

Google it for full explanation.

 

what is the ballast resistor circuit and wheres it located?

So you dont think it is the timing at all? get this when I change 2 of the spark plug wires around. it runs perfect if I hold the key over. with no backfire at all? I dont get that. I know it isnt the firing order because the other way the wires were is the way they always been and it always ran perfect. now this ballast resister circuit. I couldnt find this on ebay at all. is that a part? or something else?