1976 thunderbolt 115.

[Shadow1234]

I have read a little on this engine and people say if you have the wrong prop you can burn up the #3 piston. The prop i have is a SS 21pitch. So you think this will be the right pitch.

 

[Droll]

Re: 1976 thunderbolt 115.

I have read a little on this engine and people say if you have the wrong prop you can burn up the #3 piston.

To big a prop can AND will damage ANY outboard engine.... on the inline 6 engines the # tends to go first..

The prop i have is a SS 21pitch. So you think this will be the right pitch.

What size are your boat ?? ( length, weight, type of hull )
What WOT rpm does the engine have ?? ( WOT = Wide Open Throttle )

You should be able to reach 5500 rpm with a lightly loaded boat ( you + fuel )...

Quick example...
Got a 15 foot boat with a slightly "tuned" early 80s 90hp ( ported to 140 spec + 150hp carbs ).

• Started with a 19 pitch alu propeller.... WOT rpm was 5100
• Next tried a 16 pitch alu propeller... WOT rpm was well above 6000
• And just for fun tried a 21 pitch SS propeller.... WOT was 4800 rpm
• Ended up with a 17 pitch SS propeller..... WOT now are close to 5800 rpm

Arne Kjetil

 

[Chris1956]

Re: 1976 thunderbolt 115.

A 21" pitch prop is a bit tall for most boats with a 115HP inline six. If the boat is real light, it might be OK. I ran a 21 pitch prop on my 150HP inline, on my 16 foot avenger, which is 1000# in weight with motor. It was the most that motor could take. If your boat is heavier or has a deeper vee, it may be too much prop.