Props used on 1980s models 390 sedans/EC with 3208

[fighterpilot]

What size props and pitch were used on the 1980s 390 Sedans and Express Cruisers. With tunnels did that limited the diameter that could be used with the 320HP 3208s or did they just make a big tunnel? Going to look at one today and would like to be informed. Thanks

 

[Tanqueray]

Why not wait till tomorrow to ask? I can't even figure out what it is you want to know. I'll guarantee you the props on a 3208 and a 390 Sedan WILL be different. You say you're going to look at one today but didn't say which one.

 

[JVM225]

Sounds to me like he is looking at a 390 Sedan that is powered by 3208 Cat's and he is looking for info on the props that can be used on that particular boat.

 

[David M]

Whatever the pitch, the diameter should not exceed 85% of the distance from the shaft to the hull bottom. The clearance is necessary to preclude vibration caused by turbulence between the prop edge and the hull. 80% is better, however, 85% is acceptable.

For example, if the distance from the blade protrusion at the blade hub to the hull is 10 inches, then the absolute maximum prop that could fit on the boat would be a 20" prop. 80% - 85% of 20 inches is 16 to 17 inches in diameter. 16 inches being preferred for smoothness under the hull.

HTH

 

[fighterpilot]

jvm225-your are right, was going to look at a boat-actually did look at a boat and wanted to be a little more knowledgeable on the subject. Boat on a lift and owner said they were 24 square. With the 355HP Cat 3208 engine and the loaded weight of 25,000 lbs for the Sea Ray 390 Sedan I would think 24 square would be over propped. Wondered what others were running. Since the 390 EC and the Sedan use the same hull and in some cases the same engine I would think the proping might be similiar. Hence my question. Thanks