trim range on Volvo SX outdrive

[BartW]

the trim range on my new VP SX drives is very small,
I can only use her in max down position -7° till -6° (angle on the EVC display)
if I use a higher trim angle the prop gets air.
On my previous boats with merc Alpha1 drives, I had a play range of around 10° on the same scale.
Who has experience with VP-SX, is this due to the transom design, or is this tipical for a Volvo Penta drive ?

 

[Pinnacle]

I have an SX drive - single prop.

I don't recognise the problems you are describing. We can and do use a range from full down to a few degrees up. Tend not to do more that this cos it tries to lift the bow too much.

Is the cavitation plate on your drive level with the keel?

 

[BartW]

I have a twin installation,
the center of the cavitation plate is level with the keel,
but my boat has a small beam and still quite a deep V at the stern, so this might be the reason of my problem,
it is not really a problem as I don't need a lot of trim on this boat,
but still I was wondering

 

[volvopaul]

Sounds like the trim switch is set wrong or faulty, beware of running the leg too high you may damage the uj coupling would get it checked out by lifting the leg in the trim position, measure the amount of chrome rod that is out of the ram cylinder, there will be a max amount before the leg moves to the beach position.

 

[Bod]

I'd also be interested the experts views on this as I've notcied something similar.

Three years ago I re-engined from a AQ225 with 280 leg to a 4.3GXi with SX leg. I started off running a 19" pitched prop and had no problems as I can remember.

After changing to a 21" I noticed that any trimming away from fully down made the boat susceptable to caviation, especially in other than flat calm conditions and in moderate turns. The boat is quite flat bottomed (18 deadrise I believe).

Could the pitch of the prop make a difference? Next season I'm going back to the 19" in the hope that this will allow me to trim up a bit. I also wonder if the transom plate adapter used has left the leg in the wrong position.

Never had this problem with the old engine which gave a wide range of trim.

As to the EVC display - it was pig to setup the sensor according to the boatyard and appears to lose all contact with reality above a reading of 0.

 

[BartW]

Paul,
when the leg is fully trimmed down, EVC display say's -7°, ram cylinder fully in, no chrome visible.
when the leg is a little trimmed up, EVC just going from -7° to -6°, Ram cylinder 3,5cm chrome visible, now the cavitation plate is in line with bottom of the boat, (this is the best cruising position in flat sea)
When the leg is trimmed more up, more then -6°, I get cavitation , from here the trim range is not usable for cruising.
Beach and trail position, Ram cylinder out completely or almost completely no problem, works well
thanks for posting /forums/images/graemlins/ooo.gif

 

[volvopaul]

Sounds like the trim switch has stopped working, as when you trim out or lift the leg the reading should go from say -7 to + 7 or 8 depending on set up the rams are moving but the gauge is not telling you its moving up the scale.

 

[BartW]

I think I didn't explain very well,
the switch and the readings, all work fine,
I can easyly trim -7,-6,-4,....0.....+1,+2,+3, .....
but the usable range for cruising is very limited,
I can only use from -7 till -6,
when I trim from -6 upwards, I get cavitation or ventilation very quick

 

[TonyJones]

This would definitely be ventilation (sucking air down from the surface) as opposed to cavitation (the forming of air bubbles on the forward faces of the prop blades during acceleration).

Could it be that the drives are installed too high on the transom and are too near the surface when you are well up on the plane? I hope not: moving them down is would be a major operation.

Best wishes
TJ

 

[volvopaul]

Maybe the trim switch is set wrong.

To set the gauge at zero the correct amount of ram rod length should be set, then set the gauge to zero, the yamaha and mercruisers are roughly the same, I doubt the installation is wrong, do you have trim tabs to correct the trim angle when planing or getting on the plane, it maybe just that the leg is going too high when you trim out lifting the prop out to the surface too much, get the ram length checked.

 

[BartW]

Hi Pinnacle, could you tell me on which boat you have that SX drive mounted, is it a single or twin installation,
As you say that you can trim from -7 to lets say +3 it's a lot more than I can,
so I think that my problem must be created by the hull shape and the mounting hight of the drive.
The boat manufacturer claims it is a typical difference betweeen the SX drive, compared to the Merc drives.

 

[BartW]

Tony, yes you're right this is ventilation,
and you're probably right aswell about the mounting postion of the drive that is quite high,
I think this is typical for a twin installation in this small beam boat,(2.5m) and quite deep V at the stern.
I don't think it would have been possible to put the drive lower
and for sure not now anymore (transomcutout..etc).
But in fact I don't have a problem with it, as the boat has very good ruff sea behaviour, and cruises very fast with different loads (light and heavy weight). I can do eventual bow levelling with the trim flaps.
thanks for posting