newcdnboater
Seaman Apprentice
- Joined
- May 14, 2008
- Messages
- 40
Hi, I've got an '87 3.0l mercruiser with Alpha one drive. Engine runs extremely well on muffs but in the water (salt..haven't tried fresh) it idles rough, will stall on acceleration, backfire through carb BAD, and most times won't take any throttle at all. Once in a while it will take off and be fine...WOT (didn't take note of RPM though). It appears it could run all day at high throttle but as soon as I bring it back below 1/2 throttle, it starts to sputter and shake until stalling. I end up hobbling back to the wharf and it sounds like it's only running on two cylinders (not though..pulled each plug wire with no change in behavior). Whenever you open the throttle after the high speed trip, it just backfires through the carb.
Has new Delco plugs MR43T .035 gap. New wires, new dist cap, new points, new fuel filter, new water/fuel filter, fresh gas, timing set 6 deg BTDC and advancing, new oil and filter.
I keep checking for water in the cyl but no sign. Plugs are coming out dry and black (not sooty though) and the new oil still is crystal clear. I am now at the carb and suspect it is the cause. However, I noticed the hose from the thermostat to the block is hot, intake from raw water is cold, hose to manifold is cold...is my thermostat working properly. The temp guage never seems to go above 130, and that's on the muffs...120 in the water.
And back to the carb, I plan to do a rebild this week...it is the mercarb #1389-9350. Once I pulled the carb off, LOTS of corrosion in the intake manifold. No flaking, but it looks iminent. I'm surprised it will run at all with that much corrosion in there. This is my first boat and I'm not sure if this is normal or not.....and, could it be related to the backfire/stall issue. Doesn't seem likely but maybe.
One more thing, my ignition coil is quite hot when engine running but the heat seems to be inductive off the mount.I've heard of coils acting funny when hot. Do you think I should replace it on spec?
Sorry 4 being so long winded. Great forum. Keep up the great info/tips and help!
Has new Delco plugs MR43T .035 gap. New wires, new dist cap, new points, new fuel filter, new water/fuel filter, fresh gas, timing set 6 deg BTDC and advancing, new oil and filter.
I keep checking for water in the cyl but no sign. Plugs are coming out dry and black (not sooty though) and the new oil still is crystal clear. I am now at the carb and suspect it is the cause. However, I noticed the hose from the thermostat to the block is hot, intake from raw water is cold, hose to manifold is cold...is my thermostat working properly. The temp guage never seems to go above 130, and that's on the muffs...120 in the water.
And back to the carb, I plan to do a rebild this week...it is the mercarb #1389-9350. Once I pulled the carb off, LOTS of corrosion in the intake manifold. No flaking, but it looks iminent. I'm surprised it will run at all with that much corrosion in there. This is my first boat and I'm not sure if this is normal or not.....and, could it be related to the backfire/stall issue. Doesn't seem likely but maybe.
One more thing, my ignition coil is quite hot when engine running but the heat seems to be inductive off the mount.I've heard of coils acting funny when hot. Do you think I should replace it on spec?
Sorry 4 being so long winded. Great forum. Keep up the great info/tips and help!
