Where to find info on "loop" engine vs: "new style"

[BondoBob]

My son may be buying a 87 XP150 Evinrude and 17 1/2 foot Skeeter. I would like to know the differences between the various year motors (pros and cons). This 87 is a "loop" scavanged motor which I know describes the porting arrangment but how does that compare to later or earlier motors? More power, better fuel economy, better idiling? Is there reference material on the net? I love all motors so this is important to me. Thanks.

 

[FlyBoyMark]

Re: Where to find info on "loop" engine vs: "new style"

Most all newer motors are loopers except for a very few small outboards of each maufacturer. In general they produce more power per cu in and have outrite better acceleration and torq. Loopers tend to idle a tiny bit rougher and cross scavenged can idle all day or troll all day without ever skipping a beat. Loopers generaly use port and cylinder head shape to attain fuel flow effects in the combustion chamber where as cross scavenged use a piston with bump or baffle on the top of it with porting on opposite sides of the cylinder to attain desired combustion chamber flow. The main reason for going to loopers is simply put: more HP per cu. in.<br />As far as fuel economy, that is all based mostly on hp produced by the engine. Loopers might be more fuel efficeient at cruise and cross scavenged efficient at trolling speeds or lower throttle settings. The newest motors still use loop charged induction they just use a different newer and more efficient EFI and oil injection system to be more "green" concious. Most all of the maufactureres have a detailed description on their site with cutaway views of their motors induction system and description of their fuel charging systems.

 

[Dhadley]

Re: Where to find info on "loop" engine vs: "new style"

The 1987 XP 150's are crossflow motors. As mentioned, they dont produce the torque of a looper but they are a very solid and proven design.<br /><br />It should be a good motor for the Skeeter.<br /><br />Good luck!

 

[BondoBob]

Re: Where to find info on "loop" engine vs: "new style"

Thanks for the information.

 

[BondoBob]

Re: Where to find info on "loop" engine vs: "new style"

I checked out the boat tuesday night, only 75 psi on all cylinders. The motor had a jack plate which combined with the age had cracked the transom to the point that by lifting the motor up and down I could see the transom move 1/4 to 1/2 inch! Looking under the hatches at the attachment to the stringers you could see the cracks also. So obviously I vetoed that one. Oh yeah, the lower unit was cracked into the gears too.