Outdrive is mounted 1" off-center?

[tuantom]

Well, the title pretty much says it all. As I'm restoring a 1967 24' Piranha there are all kinds little suprises along the way. I put a new plywood transom in the boat last fall and am now ready to cut out the key hole for a Volvo Penta 270 drive. I thought I would just cut it exactly where it was by using the existing outside glass skin as my pattern; however after going over it a few times it's become apparent that the drive was mounted 1" off-center to the starboard side. Is this done on purpose? Or a simple math mistake?

This boat always had a problem with hard steering starboard. It seemed adjusting the touque fin (?) on the outdrive would only shift the RPM range that boat would pull to the left. I had it set so it would drive pretty straight at cruising speed - but at full throttle it would really want to pull. Would 1" off-center on a 7' wide hull cause this?

Thanks,
Tom

[im412]

firstly, i dont know
but a search might be worth while, there was a topic here that talked about a 6" or so offset of a prop shaft on a boat to counteract prop torque
cheers jack

[spank]

Well....that means your engine is 1" off center. This might be easily recitified depending on how your beds are set up. If this is not the case, then you will have to modify your engine beds to allow the 1" shift back to center.

[tuantom]

Yes, the engine is also 1" offset. I don't mind doing the glass work and engine mount modification to center the engine - but I don't want to do this if it is offset for a reason. I've found some very vague info after hours of searching suggesting that this could be done on purpose to counteract prop torque. nothing definitive, though. I couldn't find the post about the offset prop shaft; but it seems to suggest that there could be some reason behind the offset.
However, I measured 3 boats with volvo penta outdrives yesterday - all of them dead center. So it doesn't seem a common practice to offset the outdrive; but there must be a theory about it. Maybe low speed control? I don't know.

[nevd]

Some high performance boats offset the motor to counteract motor/prop torque. The offset direction is also correct so I suggest you do the same again - particularly if it decreases engine mount rework. I suspect the offset is however too little to have any noticeable effect.

[spank]

I would not be surprised at all if it was just off 1"....many builders have done worse. Trim tabs are always an easy option to conteract any torque issue. Alternatively, you could always mount the engine with the 1" offset and just live with it, as it isn't going to make a world of difference in the end.

[tuantom]

The boat used to have manually controlled hydralic trim tabs - they were effective for getting up on a plane; but you had to hold them down - and you would get tired of doing this after a short time. The only reason I would consider moving everything to dead center is if it would help remedy my steering issues. However, it doesn't seem as if it would help that much.
- Tom