Recent content by jimmbo

If you decide to work on this Engine, beware that a special Tool is required to position the High Speed Nozzle properly in the carb body. Also you would need to use BRP Precision Blend in the Gear Case. That is what BRP calls its Type C gear oil. While there are some 3rd party gear oils that...

Far from it. There is a lot more to Fuel Delivery Curves than just Jets.

Blade Flex, 2 words that have sold tens of thousands of SS Props. If the Blades of an Aluminium Prop Flex, it would be in the Hundreds of an Inch.

I suspect that Amazon Prop is quite a bit different from a Mercury Prop of the same Dia and Pitch. Quite a bit different, might seem like little to you, but most Boaters think a Prop is a Prop

I remember seeing that pic of the 4hp merc, 70 or 71, I recall

It is on the Band, around the Upper Gear Case

Everything has a Place, and Everything all over the Place

That pic is a 66.

Some specs for the 1970 line

"Cheap Amazon Prop" tells us nothing about the Prop you put on, other than it is 14.5 X 19 that is apparently blowing out at High Speed. Is the Hub on this Prop the same Diameter as the one you took off? What was the diameter and pitch of the 4 blade? The number of Blades is also a factor I...

Diameter and Pitch are only part of what makes a Prop. Blade Area, Blade Shape, Constant vs, Progressive Pitch, Cup, and Rake are also factors. Change any one of those, even the slightest and it becomes an Apples to Oranges Comparison Now about your Replacement Prop, does it have the same Hub...

Gonna need a hell of a set of Ramps to get the motor high enough to remove the Lower Unit to replace the Water Pump Impeller

Perhaps a Gil Bracket would have worked a bit better

Actually the opposite was the case for decades, more hp was squeezed out of a given displacement, just about every model yr. Some examples of many were; OMC's 70.7 inch block was originally, a 50hp, later becoming a 60, and finally a 65. Same went for their 2bbl 89.5 inch block, 75hp, then 80...

Just because the Displacement is the same, doesn't mean a change in Jets or Timing will turn a 50hp into a 70hp. Porting, Pistons, Exhaust Tuning, Carbs, Reeds, and other differences are things that are often different to get the differences in Hp. As for the WOT Rpm range being the same, that...