Converting from sub-surface drive to surface drive

[Kez]

I see there isn't much activities in the mono forum and I am not sure if I will get any resplies. But I will try.

I am restoring an old .40 Deepvee that was set up for sub-surface drive. The prop is 3/8" below the vee currently and I am running a X445 to 447. I am wondering what kind of performance, handling difference can I expect if I convert it to surface drive. By surface drive I mean the drive cable to exit the transom rather than under the hull.

For one thing, the surface drive set up is more scale looking. Also I think it has less drag because the stuffing tube is not under the water. It also make for a neater install.

Just want to know the pros and cons before I plug up the hole and drill new ones in the transom.

kez

 

[tnrcboatracer]

Not sure how it will handle. MIght be a little short and wide for the surface drive, buyt give it a shot.....

 

[dwilfong]

My first build 1 1/2 years ago was a DV40. I made it surface drive from the start. Had a K&B 7.5 in it.

It was very fast could not find a prop it could not run. The only problem it would chine walk real bad and blow of the water. It was a real hand full. fun boat to play with.

It might be beter sub surface will keep more boat in the water. If I had it all over to do again I would have made it sub surface.

David

 

[Michael Costanzo]

i have a older areomarine d/v 40 hull and we set it up to run as a surface drive and it went like a bullet and turned just fine. mike.

 

[Kez]

Thanks guys for your replies. While I have your attention, can you tell me how far back you have the drive dog from the transom? Also, how high up was the prop from the vee. My K&B 7.5 can turn a 447 3/8" below the vee. How much bigger prop can it turn with the surface drive set up.

Thanks.

kez

 

[tnrcboatracer]

I run X450/3 on my seaducer 45 and it is set with the shaft C/L at 3/8" above the bottom of the hull. Shaft height is used to settle the hull, and lifting props ususally don't work well on Mono's. The X452 will also work, but the 2 blade prop doesn't handle quite as well as the 3 blade on my setup.

 

[Joe Warren]

I see there isn't much activities in the mono forum and I am not sure if I will get any resplies. But I will try.

I am restoring an old .40 Deepvee that was set up for sub-surface drive. The prop is 3/8" below the vee currently and I am running a X445 to 447. I am wondering what kind of performance, handling difference can I expect if I convert it to surface drive. By surface drive I mean the drive cable to exit the transom rather than under the hull.

For one thing, the surface drive set up is more scale looking. Also I think it has less drag because the stuffing tube is not under the water. It also make for a neater install.

Just want to know the pros and cons before I plug up the hole and drill new ones in the transom.

kez

Kez, we have hashed this topic before. Boat Hulls that were layed up years ago that was orgianlly set up for sub surface. These boats had the Breaking point 4-5 inches ahead of the boats C.G. The Modern Surface drive Mono Hulls today have the beaking point only approx 2-3 inches ahead of the boats C/G. (BREAKING POINT) If you measure the boats flat ride surface underneath the boat. From the transom going forwards. At the point the flat surface starts to bend towards the Nose of the Hull this is the Beaking Point. The Boat Pivots or turns on this point. Also If you change From Sub Surface to Modern Surface Drive it effects the length of the riding surface & the wetness of the Hull a great deal. C/G Even if you have a older hull & dont know the exact C/G of the Hull from the mfg. It will end up approx @ the front of the Flywheel when you figure out where the engine belongs. You engine location will greatly determine where the C/G is. I have modified Many Mono hulls looking for more Performance. Some Mono Hulls are built for Racing Only! Some are built for Sport boating @ best......jw p.s. if you do convert this older boat mono hull you will have a boat that loads the engine hard & turns slow.