Johnson BJ60PL4 v. BJ70PL4 What's the difference????

[Capt Joe]

What is the difference between the Johnson 60 & 70 HP 4 stroke motors??<br />Both weigh 163 kG. Both have 74x75.4 Bore & Stroke. Both displace 1,298cc. <br />The only difference I can see is a slightly higher rev range 5,200-5,800 (70) compared to 4,700-5,300 (60).<br />Sorry, the other big difference of course is the price.

 

[jimmbo]

Re: Johnson BJ60PL4 v. BJ70PL4 What's the difference????

Possible differences; different carbs/air valves, intake manifolds, camshaft, spark advance. A difference in compression ratios would mean different pistons or/and heads. If the engine has a computer running it, a different map is most likely involved.

 

[Capt Joe]

Re: Johnson BJ60PL4 v. BJ70PL4 What's the difference????

I'm no mechanic, but with the same bore & stroke how can the compression ratio be different?

 

[jimmbo]

Re: Johnson BJ60PL4 v. BJ70PL4 What's the difference????

different piston tops and/or size and shape of combustion chamber in the head. Just like a car. The Chevy 350 has been made with compression ratios as low 7.8:1 and at the other end, even higher than 13:1 and the bore and stroke stayed the same.

 

[Capt Joe]

Re: Johnson BJ60PL4 v. BJ70PL4 What's the difference????

Thanks Jimmbo, There go all my arithmetic theories re length by width out the window, but I see what you mean.