View Full Version : More prop and trim questions

08-24-2010, 10:23 PM
Hello all-was finally able to get the 18 out on some relatively smooth water for some performance testing. Engine is a 351w, altitude 5500 above sea level. Prop stainless 15x21rh. Boat is a port helm.

1. Motor would only turn 4000 rpm or a little more, according to the manual I have a 351 should turn about 4400, is that correct?

2. Drive is a Volvo 270, no trim. Currently on middle of the three adjustment holes. When accelerating from a stop prop slips a little, same with slow speed (10-15 kts) tight turns. Move drive in or out or leave alone?

3. There is a pretty strong torque steer to port even with trim tab adjusted pretty far. Since I need less prop at this elevation anyway would it help to switch to left hand rotation.

Thanks for any feedback. Jim

08-26-2010, 09:10 AM
If engine sounds like it is running well, prop is wrong. Chances you have the old aluminum prop or an ultra. I sell new style SS props that don't slip.

08-26-2010, 09:24 AM
The middle setting on the Volvo 270 is usually a good all around setting for an 18. the lower setting puts the bow down too far. Upper can be faster, but I found better handling in the middle.

A port helm boat should typically have a left hand prop. You can change the rotation of the drive easily.

The older volvo drives generally have alot of steering torque at the wheel. Power steering or hydraulic steering is generally the only way to get rid of it.

What size prop do you have now. Griz can set you up with a nice one for your boat.

08-26-2010, 10:56 AM
Currently a 15x21 stainless

08-26-2010, 07:46 PM
what rpms are uoy turning?

08-27-2010, 09:02 AM
With the 15x21rh stainless the motor is maxing at 4000 making 40kts. Remember this is at 5500' altitude. Gonna try a 15x19lh. Boat is running well, jumps onto plan with just that little bit of slip.

09-01-2010, 11:36 AM
Ah left hand rotation is the way to go. Torque steer just about completley eliminated with the tab in Nuetral position. Tried a 15x19lh Volvo elephant ear prop and got max rpms at 4600. Boat road and steered much better, no slip. Can the pitch on boat props be tweeked at all? I think about a pitch of 20 would be perfect.

09-01-2010, 11:44 AM
prop pitch can be tweaked by any prop shop. You may hear some people talk about 'labbing' - that's just super-fine tuning for maximum speed. I wouldn't bother unless you are looking for that last tenth of a knot.

09-01-2010, 03:30 PM
Does it matter to pitch up or down, have a 15x21lh coming I am going to try before doing anything. But if the 21 takes rpms to low, is it better to increase pitch on the 19 or reduce pitch on the 21?

09-01-2010, 04:15 PM
I typically deal with larger props, but usually my prop shops will go 2" either direction. On a small sterndrive prop they may have a little less room to work. A call to your local prop guy will let you know if they prefer one over the other.

09-02-2010, 07:56 AM
A 19 inch Solas might be the ticket for you. They act like a slightly bigger prop and were designed for the older volvo drives. Big Griz was instrumental in getting Solas to make a high performance stainless prop for the older volvo drives.