Sorry for the long post, but I wanted to be sure to have ALL the information.
1978 "V1500" Mercury 150 HP V6
1979 "16-8" Champion bass boat
Symptoms:
Work done. All work and adjustments done according to the official Mercury manual for this motor:
Other points:
I've searched and read a lot of stuff (here and elsewhere) on my issue, and I came to the conclusion that it must be the reeds. So last night I pulled the reed block. I was planning to make a new set of carbon fiber reeds for it. But....
According to the book, the reeds are "perfect." They are clean and flat. They are all fully closed. Shining a light through from the back, no light can be seen under the reeds. They all open freely. The block surfaces under them are smooth and not indented. The limiting plates are all at the specified 0.200" gap.
So, should I go ahead and replace the reeds with new carbon fiber reeds?
Should I replace the coils just because they're old and they're the last remaining parts of the ignitions system?
Would it help to advance the timing a bit at low speed?
Should I replace the low-speed jets?
Should I just get a new fuel-injected motor? (Just kidding on that. Can't afford it.)
1978 "V1500" Mercury 150 HP V6
1979 "16-8" Champion bass boat
Symptoms:
- When trimmed down for idle and no-wake operation, seems to "load up" with fuel. Burns very rich. No-wake operation is difficult at best. Will stall if throttle is applied too quickly in gear.
- Hole shot? What hole shot? Throttle must be applied gradually, or it will just bog or stall. Can be helped by trimming up, but then the boat's attitude is all wrong for coming up.
- Long crank time on cold start. Pump the bulb up hard. Engage choke (key in). Open throttle slightly. Total crank time over a minute (in proper short bursts). Hold key in for a moment after start. (No "fast idle lever" on this motor.)
- After running, will start almost instantly all day long.
- At speed, no problems.
Work done. All work and adjustments done according to the official Mercury manual for this motor:
- New head gaskets. Compression balanced 110-120 per cylinder.
- New thermostats.
- Fuel pump rebuilt.
- Carbs totally rebuilt. All jets, ports, passages are clean and clear. Jets are correct sizes and not worn out. Float levels set "by the book."
- Carbs synchronized "by the book."
- Both ignition boxes are new.
- Replaced OEM-type "surface gap" spark plugs with extended-reach conventional gap plugs of correct heat range. (Made a MAJOR improvement in running, but didn't help this issue. Yes, there's plenty of clearance to the piston tops.)
- New plug wires.
- Ignition timing set "by the book."
Other points:
- The carbs have NO idle mixture adjustments. The only way to affect idle mixture is to adjust the float levels (for only a slight change), or replace the jets.
- I have not replaced the coils. They are the originals. They seem to be firing just fine, and pass all diagnostics "by the book." This does not appear to be a spark issue.
- I have two props, a 3-blade stainless Hoss, and a 4-blade composite Piranha. Both are properly sized for the boat and motor, 5500 rpm at WOT.
I've searched and read a lot of stuff (here and elsewhere) on my issue, and I came to the conclusion that it must be the reeds. So last night I pulled the reed block. I was planning to make a new set of carbon fiber reeds for it. But....
According to the book, the reeds are "perfect." They are clean and flat. They are all fully closed. Shining a light through from the back, no light can be seen under the reeds. They all open freely. The block surfaces under them are smooth and not indented. The limiting plates are all at the specified 0.200" gap.
So, should I go ahead and replace the reeds with new carbon fiber reeds?
Should I replace the coils just because they're old and they're the last remaining parts of the ignitions system?
Would it help to advance the timing a bit at low speed?
Should I replace the low-speed jets?
Should I just get a new fuel-injected motor? (Just kidding on that. Can't afford it.)