Tunnel Hull Cavitating Pics

[89 redfin]

It appears that cavitation plate is about 2 inches above the top of the tunnel.

So is this why it is cavitating out of the hole,?

 

[89 redfin]

trying to upload pics are a problem.

 

[Watermann]

The correct term may be 'ventilation' where the prop being too close to the surface pulls in air. The plate above the prop is a the AV 'anti-ventilation' plate and it should be right even with the bottom of the hull with the motor trimmed down.

Photo bucket accounts work best here and paste the IMG code into the post.

 

[89 redfin]

got it!

I thought as much as it is 2 inches above trimmed all down, will instal fixed jack plate and lower it 2 inches and repost.

THANKS! to everyone who commented!

 

[mrdancer]

got it!

I thought as much as it is 2 inches above trimmed all down, will instal fixed jack plate and lower it 2 inches and repost.

THANKS! to everyone who commented!

You'd probably be better off with a hydraulic jackplate, if you can swing it.

The anti-ventilation plate on my engine sits about 2-3" above the top of the tunnel, and it works just fine. However, it has a custom tunnel prop (Blaster) on it from Baumannprops.com . A good tunnel prop (extra cupping, large blade surface area) works a lot better at grabbing the aerated water coming out of the tunnel. Give Louie or Matt at Baumann a call and they can get you set up properly.

 

[metriccrescentwrench]

T.....The plate above the prop is a the AV 'anti-ventilation' plate and it should be right even with the bottom of the hull with the motor trimmed down......

Proper engine height depends on a lot of factors including hull design, engine setback, prop selection etc. For instance, my Checkmate is perfectly happy with the AV plate about 7 inches above the bottom of the pad. But here the OP is talking about a tunnel hull which is different than my Pad-V, which is different than a V hull, etc.

 

[Stumpalump]

Everybody thinks the cavitation plate needs to be a specific height above or even with the bottom. Wrong because all boats are different. It's trial and error and some boats need to be below the hull to perform. I just dropped one an inch below and gained 2 mph. The next boat may run fine inches higher. People think they can eye ball it and say it's right. Nope and the fallacy is so widespread that company's sell hundreds of electric jack plates to the fools that think they need to adjust it all the time. Wrap your brain about what it's doing with max trim and max speed. Set the height so it performs at top speed with no cavitation and with just a little room to trim up beyond that. Reread the last sentence a few times and set the height to that and that only.

 

[mrdancer]

Ummm, this guy is dealing with a tunnel hull. To get the most out of a tunnel hull, you need an adjustable jackplate. Yes, you can just set it and forget it, but that is like having a 4wd truck and never using the 4wd feature - IOW, why have a frickin' tunnel if you can't take advantage of it? They are hugely inefficient compared to a standard hull, so if you got it, you should use it to its full effect and at least get a little payback.


On my boat, and most all other tunnel hulls that I am aware of, you drop the jackplate to get a good holeshot, then raise the plate to either 1) run through shallow water, or 2) gain better performance while on plane, or both. You can't have both at one setting with a tunnel hull. The adjustable jackplate also makes a huge difference if you're varying loads a lot - i.e., your boat is loaded with people/cargo one day, and just you and a buddy the next day.