Twin 1984 Mercruiser 470s with alpha 1 drives
-info for both engines-
*Compression good/even - starboard engine 140,138,140,140 port 134,132, 135,135
*New plugs properly gapped per factory manual
*New cap, rotor, points, condenser
*Point gap/dwell set per factory manual
*Timing set per factory manual
*Automatic chokes, clean and functioning
*Engines run off a common tank. The tank was drained and filled with fresh gas before we started them the first time and as we have been using the boat some, we have run about 120 gallons through the system and changed the filters 3 times just to make sure there were not too many ?nasties? clogging things up.
*With about 15 hours of run time on the plugs, they are barely taking a tan/lt brown color.
Both engines, once started run GREAT. They are smooth at idle and all the way up to high rpms whether they are gradually accelerated or the throttles are slammed wide open. There are no hesitations or backfires.
My problem is that when trying to START these engines when they are COLD, BOTH of them backfire through the carburetor and must be cranked a lot, most of the time pumping the gas helps. After they are warm, they start with just a quick bump of the key ? no touching of the throttles.
I have disassembled, cleaned and rebuilt the port engine carburetor. It was very clean inside. This has not changed the start up of the port engine at all.
BOTH engines backfire when trying to start them cold.
These engines were not run for a couple years, and the boat is new to me so I do not know much of the history. One engine is definitely newer and the PO confirmed that he had to replace it due to massive water intrusion due to exhaust/operator failure.
Another thing I have tried is moving the timing to TDC and slightly retarded, but no change in how they start when cold. I put them back to the factory manual setting.
If anyone has made it this far-thank you-, I have run out of things to try.
Any ideas?
-Kyle
-info for both engines-
*Compression good/even - starboard engine 140,138,140,140 port 134,132, 135,135
*New plugs properly gapped per factory manual
*New cap, rotor, points, condenser
*Point gap/dwell set per factory manual
*Timing set per factory manual
*Automatic chokes, clean and functioning
*Engines run off a common tank. The tank was drained and filled with fresh gas before we started them the first time and as we have been using the boat some, we have run about 120 gallons through the system and changed the filters 3 times just to make sure there were not too many ?nasties? clogging things up.
*With about 15 hours of run time on the plugs, they are barely taking a tan/lt brown color.
Both engines, once started run GREAT. They are smooth at idle and all the way up to high rpms whether they are gradually accelerated or the throttles are slammed wide open. There are no hesitations or backfires.
My problem is that when trying to START these engines when they are COLD, BOTH of them backfire through the carburetor and must be cranked a lot, most of the time pumping the gas helps. After they are warm, they start with just a quick bump of the key ? no touching of the throttles.
I have disassembled, cleaned and rebuilt the port engine carburetor. It was very clean inside. This has not changed the start up of the port engine at all.
BOTH engines backfire when trying to start them cold.
These engines were not run for a couple years, and the boat is new to me so I do not know much of the history. One engine is definitely newer and the PO confirmed that he had to replace it due to massive water intrusion due to exhaust/operator failure.
Another thing I have tried is moving the timing to TDC and slightly retarded, but no change in how they start when cold. I put them back to the factory manual setting.
If anyone has made it this far-thank you-, I have run out of things to try.
Any ideas?
-Kyle
