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  1. jimmbo

    Estate sale lot of 18 - 25hp motors - Compression gauge variables.

    Felt Air Cleaner? For the past 50 years I have seen nothing but Foam Filters on Chain Saws, so that one you are referring to, must be really old
  2. jimmbo

    Prop Selection - Bayliner 175

    I reread the Thread, I didn't see anything Insulting...
  3. jimmbo

    Estate sale lot of 18 - 25hp motors - Compression gauge variables.

    The Bearings would be gummed up real quick
  4. jimmbo

    Prop Selection - Bayliner 175

    Maybe you need to get a Prop with Vent Holes to improve the Hole Shot
  5. jimmbo

    Estate sale lot of 18 - 25hp motors - Compression gauge variables.

    A 2 Stroke Engine would not last very long if it were inhaling Wood Dust, and it wouldn't be Build Up in the Combustion Chamber that kills it
  6. jimmbo

    Estate sale lot of 18 - 25hp motors - Compression gauge variables.

    I think the only engines that had the Decompression Feature were the 57 - 59 35hp, and the 60 - 61 40hp
  7. jimmbo

    Estate sale lot of 18 - 25hp motors - Compression gauge variables.

    The 25s, have a different Cylinder Head from 18/20s, to make up for the Lower Piston Height in the 25. If someone stuck a 25hp head on an 18/20, then the Compression would be high enough to cause Detonation. But I doubt even that mismatch would have 200psi. Maybe with a very large Carbon Buildup...
  8. jimmbo

    What could cause this

    VRO didn't come out until 84 Only the Intake Side is scuffed/Scored, and the Exhaust Side is Fine?
  9. jimmbo

    Timing is retarded ;-)

    As other mentioned the module in the Distributor controls the Spark Advance. If it is pooched or is the wrong one(you don't know the Servicing/Repair History), the Timing Advance could be off(man I hate Electronics on engines. My I/O has a Distributor with good old fashioned Weights). That could...
  10. jimmbo

    Prop Selection - Bayliner 175

    There is a Check Valve in the Compression Gauge to allow the gauge to eventually measure the Max Pressure. If that valve wasn't there the Gauge would drop as the Piston descended. When the Gauge is connected the actual Compression Ratio drops a bit as the Gauge adds Volume to the Combustion...
  11. jimmbo

    Transom replacement or design flaw?

    People use those to buy time on a Fiberglass boat with a Rotted Transom "I think the boat is actually from the mid 90s. The reason I posted is because even with the 5hp outboard, I was getting a lot of transom flex. I don't want to replace the wood in the same configuration and end up with the...
  12. jimmbo

    Prop Selection - Bayliner 175

    Most V6 Outboard Props are the same as I/O Props If it is a dog and you are turning 5300, which above the RPM Range for that Engine, it is going to have even slower acceleration with greater pitch. 171, 182, 181,171 for compression Numbers? That engine has about 8.5:1 for a Compression Ratio...
  13. jimmbo

    1981 Mercury 7.5 2 stroke

    They can't label and market 2 two engines as different HP when there is no Difference. There is a difference between the two
  14. jimmbo

    1981 Mercury 7.5 2 stroke

    There is some difference in the Motor for the Difference in Horsepower
  15. jimmbo

    Outboard ran without water for about five minutes

    In 1976, I ran a 5 1/2 for more than 2 hours in a Barrel at about 1500 in Gear for 3 hrs to dry it out after I flipped the boat it was on. Water didn't seem to get very warm
  16. jimmbo

    Prop Selection - Bayliner 175

    If the boat is a Dog with a 17, it will be even slower, maybe not even able to plane with a 19. The 3 liter was geared quite low and usually came with 21 -23 inch pitch Prop. You are propped very low, and normally that engine would be severely over revving with a 17 inch. What is the Gear...
  17. jimmbo

    1981 Mercury 7.5 2 stroke

    Older Motors had 3 Rings, improvements in Ring Technology, enabled the 3rd Ring to be removed, reducing Friction. The Blocks, while both are Lightning, as mentioned above, have different Porting, and thus are different Part #s
  18. jimmbo

    Timing is retarded ;-)

    It sounds like this Engine may have been overheated. If you have done a Compression Test, what were the Results? If you haven't, do one, before going and spending money.
  19. jimmbo

    1981 Mercury 7.5 2 stroke

    Something is Different for the Peak Torque to be in a higher Rpm Range
  20. jimmbo

    Timing is retarded ;-)

    No Knock Sensors, they are designed to burn Reg Gas. Comparing a Boat Engine to a Car Engine, is an Apples to Oranges Comparison, even when it comes to Engines like the 4.3, the 5 liter, and the 5.7 liter. Completely different Operational Parameters
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