How do they gain 20 hp between the 40hp and 60hp

[schweg2]

My question is if the bore and stroke are the same between a 86 40hp and 84 60hp and the pistons have the same part# and the carbs take the same rebulid kit, how do they make 20hp?

 

[rodbolt]

Re: How do they gain 20 hp between the 40hp and 60hp

hello<br /> they make it very well. <br /> it can be by port timing. primary and secondary compression changes. carb jetting and exhaust tuning.ign timing or max RPM. lots of ways to make power.<br /> just remember its an air compressor.<br /> good luck and keep posting

 

[Dhadley]

Re: How do they gain 20 hp between the 40hp and 60hp

On a 40 the reed stops are set closer than on the 60. The carbs and cylinder head are slightly different too. You could open up the stops -- personaly if I were going to all that trouble I'd install Boyesen reeds. Either way dont expect some monumental difference. The torque is only slightly different. Remember, youre still dealing with the same bore, stroke, gear ratio, intake volume, exhaust volume and port timing.<br /><br />Good luck!

 

[G DANE]

Re: How do they gain 20 hp between the 40hp and 60hp

Take my advise: If you bend reed stops back, at least install new reed leafs, or better Boysens as Dhadley says. I did that once, only to loose a leaf. Luckily I found it behind a bypass cover ( it was on a crossflow ) after a total disassembly of motor. If it had went on, i wouldnt have needed the disassembly, only a garbage can. The power benefit was only minor, as I didnt have the port changes with it. The difference between the 40 and 50 looper is only reed assy, if you want to change I would look for a complete 50 assy on e-bay. There are porting etc. needed to get to 60 which has a different block.

 

[schweg2]

Re: How do they gain 20 hp between the 40hp and 60hp

I have a 60hp powerhead that I was going to put on my 40hp. I looked at boyseen reeds and the part#'s are the same for the 40 and 60hp. So are they the same you think?

 

[SCO]

Re: How do they gain 20 hp between the 40hp and 60hp

We need forktail for this answer. I can add power is the amount of work per second, and that a quantity of work(aka energy)is the torque times an amount rotation angle(of the prop or crank).You can rotate the prop through that angle in a minute, or in a second, but the same amount of energy is consumed. Torque is not energy or power. You can apply torque to a prop that is frozen and no work will be done, no work per second (power) will be generated. More power is when you consume those quantities of energy more rapidly. So, if you have a motor set up for it's max torque at lower rpm, then you get less power. I would think torque /power/rpm curves would look similar though, so it still doesn't make sense to me. Can anyone point us to some online power curves of various engines?

 

[G DANE]

Re: How do they gain 20 hp between the 40hp and 60hp

Each revolution of motor delivers a certain amount of turque. If you can make motor breathe better by changing carb, intake, reeds and exhaust tuning, it will deliver same torque amount more times pr minute ( rpm ) and perform better = more HP. Reed Leaves are the same for all, but stops are different. Changing reed stops only will only make minor difference.

 

[Dhadley]

Re: How do they gain 20 hp between the 40hp and 60hp

The Boyesen reeds are the same for the 40 and the 60 in question. Actually the reeds are the same as the V4 and V6 crossflow reeds. And the 60 degree reeds.

 

[schweg2]

Re: How do they gain 20 hp between the 40hp and 60hp

So I ordered some boyesen reeds...do I need to rejet my carbs now?

 

[Dhadley]

Re: How do they gain 20 hp between the 40hp and 60hp

Does the motor sneeze at idle now?

 

[schweg2]

Re: How do they gain 20 hp between the 40hp and 60hp

Yes it does.

 

[Dhadley]

Re: How do they gain 20 hp between the 40hp and 60hp

OK. Richen up the idle circuit until it stops. Do this before you install the Boyesens.<br /><br />Dont forget that if your carbs have air jets in the idle circuit you have to go smaller to go richer.

 

[BRIAN03]

Re: How do they gain 20 hp between the 40hp and 60hp

Mad EFI makes a 6-71 blower for these engines. If they dont have it in stock they can build it for you. They have EFI systems,light wheel flywheels, and MSD ignitions systems for this engine. I think the problem is they dont make any props to turn this big horsepower. good luck. Or you could buy a New bigger Yamaha You can Email me for a one on one conversation. I learned that here