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  1. 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
  2. jimmbo

    1981 Mercury 7.5 2 stroke

    There is some difference in the Motor for the Difference in Horsepower
  3. 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
  4. 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...
  5. 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
  6. 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.
  7. jimmbo

    1981 Mercury 7.5 2 stroke

    Something is Different for the Peak Torque to be in a higher Rpm Range
  8. 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
  9. jimmbo

    Timing is retarded ;-)

    Doubt that Engine has a Mechanical Timing Advance, but rather an Electronic Advance. How long have you had this Boat? Do you have any Service History?
  10. jimmbo

    1981 Mercury 7.5 2 stroke

    Are both Engines the Same Displacement? Were the Camshafts, the Heads, the Pistons, Intake Manifolds and Carbs, all the same Numbers on both engines. Something is different to move the HP and Torque Peaks to different rpms. When it comes to Outboards, I am more familiar with 2 strokes, and...
  11. jimmbo

    Transom replacement or design flaw?

    How much HP is the Boat rated for?
  12. jimmbo

    1981 Mercury 7.5 2 stroke

    Even with the Evidence shown in your Pics, many will still insist they turned a 7.5 into a 9.8 with a Carb swap, and even though it now runs worse at low and mid rpms, it gave them 5 or 6 more mph.... Heck, some even claim just the Carb Jet alone will does it Sorry for that Rant, but...
  13. jimmbo

    kiekhaefer

    Those tilted forward Powerheads, also have their Carbs facing slightly downward, while this may be great for having fuel spill in the the lower cowl, and in the water instead of puddling at the back of the Carb-Reed Block, it also, depending of the Carb Design, can make setting the Float in the...
  14. jimmbo

    Transom replacement or design flaw?

    Actually that plywood doesn't look as bad as a lot I have seen. I will assume that the Boat was from the 70s, maybe early 80s, so 45+ years. Another piece of Marine Plywood, will probably outlast most of us on this Board Doubt there is any Advantage to adding a Knee, if 5hp is all you plan to use
  15. jimmbo

    Few questions.

    Still haven't
  16. jimmbo

    Few questions.

    Looking at the bottom Picture, I think someone took that linkage apart, and put it together wrong, mainly that Tilt lock(#47), looks like it should be turned around. Installed as it is, it is preventing the Lock/Unlock Lever(#66) from moving However, what Motor do you have? That would make it...
  17. jimmbo

    Listing to port side

    I have never seen a setup like that before I would to see more Pictures of this Hull, from the Front, and with the Motor lifted.
  18. jimmbo

    Gph at various rpm...thoughts?

    Here is some of the Mercury Documentation of the Prototype Black Max compared to the I6 1972 1400. The 72 1400 had better Hole Shot than the I6 1500 that followed in 73
  19. jimmbo

    Gph at various rpm...thoughts?

    It took a little less than a 1/2 hour to burn through the 5 Gal(Imp) Tank. I guess that would be about 13 1/2 gal(US)/hr. It got about 4mph at WOT, it was really good at about 38 mph, a Tank would last over an hour All the Motors I listed above were Broken in by myself and were in good...
  20. jimmbo

    kiekhaefer

    I don't have 63 on file, but here is a page from the 62 Brochure
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