So you have a completely different prop replacing the old one, so results are going to be different. There much more a Propeller than just Diameter and Pitch.
You say the Solas has thicker Blades. Thinner Blades are more Efficient than thick Blades. Contour, would be referring to the Blade's...
Yo say you replaced it with a 'Same Spec' Prop.
Same Brand, and Model?
How old was the so called Factory Prop?
Was the old Prop Vented?
Do both props have the same Blade Shape, Contour, Rake, and Cup?
I guess there could be a Typo on the Chart. Where it lists 5 1/2 and 6, it probably should state 1954 - 1965, the listing for 6hp should be be 66-thur 76. It was from one of OMC Accessory Catalogs.
Yours is a completely different Tilt-Trim System than what was used in 1973, and you are correct to use ATF in it. However the previous design used SAE 20 as the fluid.
You cleaned the carbs last year? Did you drain them, or use a Fuel Stabilizer, prior to the Winter Layaway?
When you were cleaning them, did you remove the Core Plugs, especially #5, and get the gunk out of there? Is #38 in good Condition?
Could be a leaky Gasket between the Carb and Intake, and/or a leak between the Intake and the Crankcase. Link and Sync out of adjustment. Low Float Level, bad Gaskets in the Carb, dirt/Gum/Varnish in the carb circuits, to name a few
The Marine Interstate Battery that came with my Boat still had 75% Capacity at 14 yrs, tested at the Interstate Store. It seem to garner a lot of attention from the Staff. I traded it in on a new one, that was 8 yrs ago.
Welcome to iboats
I suspect that engine has an Oil Mixing System, and the Oil is kept in a Separate Tank. I also doubt an Engine requiring the use of Premixed Gas, would have lasted 2 hours if run without Oil
I used the Enertia as a Example as to what is possible with a Blade Design. My Avatar pic, was shot when the Boat had an OMC RAKER, that used to be on my 150 FICHT(had to replace the Rubber Hub to a VP) I don't think the Enertia is made in a size that will fit on a 115hp engine.
