Volvo/Penta Rooster Tail

[cnewman]

I recently purchased a Four Winns Freedom 180 with a 5.0L Volvo/Penta.
This is my first Volvo/Penta boat and came across something I've never seen:
When I'm trimmed at certain speeds I see a roster tail that originates from the I/O Unit. Is this normal? It seems to occurs when I'm trimmed down and varies with speed.

Thanks for your help,

Chad Newman

[Corpus Skipper]

How much of a rooster tail are we talking about? The drive shouldn't create much of a tail, unless it's trimmed way up. Is there a sounder transducer or something mounted near the drive? This could be the cause of the tail.

[BoatingSlave]

I have the same issue. I have a '98 Four Winns 205 Sundowner and when I am on a plane I have a rooster tail. I have a Volvo Penta 5.0L GL with the SX Cobra outdrive. The rooster tail is very noticable, about 2 - 3 feet high. It appears to be coming right of the outdrive itself and there is actually 2 tails. The only thing I have attached to the transom is a paddle wheel spedometer. The paddle wheel is more to starboard and the tails appear to be at the center. I have the same effect with a 3 blade (14 1/2 x 19) or a 4 blade (14 1/2 x 18) prop.

Any insight would be greatly appreciated.

Thanks,
Jim

[gonzo]

With the boat on the trailer, trim the drive all down. The cavitation plate lower surface should be flush or about 3/8" higher than the keel. They may be installed too low.

[Willallison]

I'd have to agree with Gonzo. Chances are that what you're seeing is not actually a rooster tail - water being thrown into the air from the blades of the prop - but spray coming off the lower unit if it's mounted too low. If this is the case, the water will tend to spray up and to the side and probably from near the front of the lower unit. A rooster tail will eminate from the back of the cav plate and will shoot directly backwards

[BoatingSlave]

Forgive my ignorance this is my first I/O, if the issue is that the outdrive is to low what would need to be done to raise it? I know with an outboard raising it up is not a huge undertaking.

Thanks,
Jim

[gonzo]

If that is the case, the transom opening needs to be recut.

[BoatingSlave]

I checked the outdrive in the down position and it is not below the keel. It is roughly 3/4" above the keel. Could this also cause the problem? If so, I am guessing that the sam solution would still apply, recutting the transom. If not, any other ideas or suggestions?

Thanks,
Jim

[gonzo]

Does the rooster tail disappear if you trim the drive up?

[BoatingSlave]

No, it doesn't dissapear. It seems to have less height when I trim up but then the boat begins to purpoise. Would a hydro foil help the situation?

[dereksireci]

I've never worked with Volvo but I know that Merc outdrives can be fitted with a spacer to lower them. On new boat models we always started out with the drive rather high (large x-dimension) because it is easier to lower than raise.
djs

[gonzo]

I'll call Bob Crocker (Volvo-Penta product developing manager) and ask him about the problem. From what you tell me it has been going on for a while. It may take a couple of days for a response.

[gonzo]

The official answer from VolvoPenta is:
Use zinc part number 3857857, this will reduce the spray.

Originally Posted by gonzo

The official answer from VolvoPenta is:
Use zinc part number 3857857, this will reduce the spray.

I have recently bought a 1998 FourWinns with a Volvo Penta. I have noticed a rooster tail also, when u talk of zinc part number 3857857 what are u referring to. Remember i know very little of these engine. Thanks for your help.

[Frans X L]

Check the transom /bottom junction. IE do you have a sharp edge, or is it slightly rounded. For a planing boat the bottom edge of the transom must be sharp or the water follows the curve and shoots upwards. You could err on the side of sloping downwards, ie having a slight 'hook' in your bottom as they say. any convex shape in the aft 1m (3 foot ) of a planing hull is going to cause problems with handling.
The thing to do is to place a straight edge on the bottom at the transom. You should not see more than a few mm of daylight for a fast planing hull.