Engine spacing??

[VCinRI]

I have seen some of the larger Grady's with engines spaced what looked to be 36" or more.
Could anyone tell me the benefits or draw backs of wider than normal spacing? Is cavitation a possibility at hard turns?
Does it maneuver better at the dock?

Thanks,
VC

 

[seasick]

I have seen some of the larger Grady's with engines spaced what looked to be 36" or more.
Could anyone tell me the benefits or draw backs of wider than normal spacing? Is cavitation a possibility at hard turns?
Does it maneuver better at the dock?

Thanks,
VC

There are recommended spacings from the manufacturer that takes a lot of factors into account and like a lot of things is a compromise. The most important factor is prop height relative to the hull and resulting water flow. Moving the spacing may also put the props in non optimal flow areas. You are correct that wider could mean that a prob may partially or completely raise out of the water on turns. Handling at low speeds may be better or worse, it's hard to say, but it could be worse if both motors are the same rotation since prop side thrust will be acting at a greater leverage length.
Trimming of motors may have more dramatic effects on handling since the thrust will be farther away from the center of floatation. Trimming range may also limited since the props could come out of the water at smaller angles especially when the boat leans.

 

[BobP]

Grady probably did ample sea testing to be sure nothing negative occured with handling as they widened the spacing. The stern of the larger gradys does look a little naked to me with the usual spacing. Spacing was always to Yamaha spec which is a minimum spec. The same industry spec applied to every motor brand (V6) wih one exception; Yamaha Fs, they couldn't design the new 4 stroke motors narrow enough to retrofit twins in standard drillings, everybody else did.

V8s are on their own with 6 bolt mounts.

 

[VeroWing]

A very general "rule of thumb" on engine spacing is, narrow spacing for better performance, and, wider spacing for better handling. Of course there are many more variables to take into consideration when mounting multi outboards.