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  1. jimmbo

    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    There are a few more contributors on iboats that have access to MercNet. However, being it proprietary, they are limited to what they can openly reveal.
  2. jimmbo

    Evinrude 90HP won’t go over 2000RPM

    A 3/8" Gap is for testing the Ignition System's capacity to supply a Spark strong enough to jump a gap of 0.030" when the Spark Plug is subjected to the Conditions inside the Combustion Chamber on the Compression Stroke Something has happened to cause a loss of more than 50% of the Engine's Rpm...
  3. jimmbo

    Engine misfires after rain storm

    High Humidity, which can happen when it rains, can wreck Havoc on Plug Wires. It can also help create conductive Paths on the Ceramic Insulator of the Spark Plug, especially if that Insulator is cracked Outboards can be just as finicky, the newer ones, with all the Electronics, even more so
  4. jimmbo

    Evinrude 90HP won’t go over 2000RPM

    What was approx 3/8" gap? A regular spark plug has a gap of 0.030", 3/8" is 0.375", almost 13 times wider
  5. jimmbo

    Evinrude 90HP won’t go over 2000RPM

    All the Cylinders getting fuel? If not, they aren't getting Oil. What do the Plugs look like? As for Good Spark, is it good enough to jump a 3/8" gap? Have you tested the Compression?
  6. jimmbo

    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    However since you don't know the Service-Repair History, what is the Gear Ratio of the Outdrive currently on the Hull? What is the Manifold Vacuum at Idle, and at WOT, read from an actual Vacuum Gauge? I know on my 5.7 it is 18" at Idle, and 4.5" at WOT with the 500cfm 2bbl, and with the...
  7. jimmbo

    Rectifier Upgrade

    An Unregulated Charging System hitting 16 volts in pretty much normal at high Rpms. Those charging systems don't put out much Current, and simply use the Battery(Wet Cell ONLY), as a sacrificial Reservoir, boiling when the Voltage is high. After the drain on the battery, from cranking, and use...
  8. jimmbo

    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    Low vacuum, as well as an Inverted Vacuum curve, I would be inclined to think the Sensor that monitors it defective. In Post #24 you said the Boat-motor was new to you, so you haven't got the repair History of it. I assume this below the WOT range of this motor, rpm you posted is how it has...
  9. jimmbo

    Mercruiser 4.5l low vacuum, WOT 4350 and higher fuel consumption

    How long have you owned this Boat and Motor? Before this low rpm issue came about, what Rpm was it getting at WOT?
  10. jimmbo

    Need HELP identifying motor first

    Idle speed is set in Gear, under load, and is generally 600rpm, give or take 50rpm. 1100 in Neutral, will do a lot of Damage to the Clutch Dog, and Gears. Do you have the correct Factory Service Manual for the Motor? If not, get one. It will have the correct Specs and the process of the Link...
  11. jimmbo

    Bass boat trim authority sucks in mid range

    Those POS, are also for pushing the Bow Down Here are some general suggestions as to what Height the Engine should be mounted. Choice of Prop, is also a factor as to how high it can be raised. That said, Heights higher than Flush with the Hull, only start to offer benefits above 45-50mph
  12. jimmbo

    Linkage Slop

    Cable may need replacing. In the 60s the Cable Ends could be tightened when they got loose. I don't know if the Silver Item, between the Thumb and finger is actually Screw
  13. jimmbo

    1986 Mercury 9.8 110 outboard

    Air-Fuel, Compression, and Spark at the proper time and it should fire. You have fuel, in the cylinder What are the Compression Numbers?(this is a very long thread) You have Spark at the Plug Wire The chances of both Plugs being bad is unlikely Maybe the Spark Timing is was off Maybe there is...
  14. jimmbo

    1986 Mercury 9.8 110 outboard

    It appears to be functioning, but once it warms up, it could become unstable.
  15. jimmbo

    Sputtering Johnson V4 90hp - 1994

    Having the same Splines, doesn't mean it is going to fit properly.
  16. jimmbo

    Sputtering Johnson V4 90hp - 1994

    Well few of us have Oscilloscope ears, and that is why a tach is the most important gauge you can ever have on a boat
  17. jimmbo

    Sputtering Johnson V4 90hp - 1994

    Too bad we can't hear the motor. What Rpm did she reach?
  18. jimmbo

    Bass boat trim authority sucks in mid range

    I feel, that it just comes down to trying to operate the Trim in a matter that is outside the Parameters for that Speed. Leaving the Old Lady at the dock or at home, will allow him to go faster, and be able to trim the motor up higher.
  19. jimmbo

    1984 Mercury Black Max 150 hard start and wont idle.

    Welcome to iboats At 4800 that engine is overloaded, WOT range for that motor is 5000-5500 Before you start throwing parts on it. Start with the Basics: Can the Ignition System provide a Spark Strong enough to jump a 3/8" gap on every cylinder? What did the plugs look like? Are the Carbs clean...
  20. jimmbo

    4.3 Mercrusier carb questions

    I have always used Lacquer Thinner for cleaning carbs, taking care not to put any plastic parts in it, Parts come out of it clean, not oily like a lot of Carb Cleaners, dissolves gum and varnish very quickly too
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