Cav Plates? Who needs 'em and why?

[specrocz]

I have seen many Spectras here on RD's and have noticed some with the full cav plates and many without. I have a 24xs, BBF, V-drive that has no plates and I think it rides excellent, however I haven't rode in a boat equipped with them. Sometimes while riding at cruising speed and higher, the steering is less than responsive in respect to wheel input vs. the boat actually turning. Sometimes I gotta crank the wheel a full turn to get the boat starting to turn. I've heard this was common in v-drive boats. Do the cav plates affect the steering? I've had this boat for 15 years and probably will never part with it. Just thinking about things to do to make it better and maybe faster.:cool:

[CampbellCarl]

My 24' Howard (splash of your Spectra hull) also has no plates. I'm told that there is a sizable 'hook' built into the bottom that helps the boat roll-over onto plane and no plates are needed.

Mine also don't turn worth a shit, I was given a turn fin (mine doesn't have one) that I have not yet installed. Does your Spectra have a turn fin (about where the v-drive is located)?

CC

[specrocz]

Yes mine has the skeg or finn that attaches just about a foot foreward of the V-drive unit. Once the boat is into a turn, it carves the water nicely. It's at about 35+ mph and in a bit of a chop, I'll need to crank the wheel a whole turn before the boat responds. Makes me not want to let any novice drivers take the helm. :drnkfr

[CampbellCarl]

I wonder if the spacing from prop to rudder has something to do with it......

Seems like there is a BIG distance and if you imagine that the prop wash is headed downward, how much is hitting the rudder surface?

I'm gonna measure mine tonite (prop to rudder) and report back. Yours looks WAY to far apart (maybe effecting the turn).

CC

[RiverDave]

I wonder if the spacing from prop to rudder has something to do with it......

Seems like there is a BIG distance and if you imagine that the prop wash is headed downward, how much is hitting the rudder surface?

I'm gonna measure mine tonite (prop to rudder) and report back. Yours looks WAY to far apart (maybe effecting the turn).

CC

That picture it looks WAY WAY WAY too far apart..

RD

[alohajeff]

Looking at those pics... That is about how mine is setup. My buddy also has a 24XS and his prop to rudder distance is the same as mine. Both of our 24XS's have the turn fin. My steering is a single cable jobber run down the port side. It turns much better when the cable is pulling and very poorly when the cable is pushing. One of the things that I am looking to upgrade is the the steering helm and cable setup. I would like to run another cable down the other side to balance out the effort it takes to turn.

Oh yeah... my prop has just enough gap between the strut to get a puller in there. Originally I had an inch gap and I cut the shaft down in an effort to get the boat freed up.

The previous owner installed a twin ram trim tab setup. After I cut the propshaft down the tabs became more necessary and noticeable. The tabs do not help steering feel, the additional bow load makes the steering feel even heavier. The tabs do however help when the chop comes up. I can plant the bow and motor right through it. The ride is smooth enough that in 2-3' chop the boys can nap.

Aloha

[specrocz]

I measured my distance from prop shaft to rudder and it came out 10.5 inches. How does that compare to anyone out there?

[CampbellCarl]

I measured my distance from prop shaft to rudder and it came out 10.5 inches. How does that compare to anyone out there?



My Howard 24' is 8" from tip of prop shaft to leading edge of rudder.

CC

[75 Spectra V-Drive]

My 20' used to have Bennett trim tabs, if you not going fast this is a great option. lets you adjust for many different conditions. ( fat guy driving ) Seems crazy to me you have zero trim control as it sits. my prop to rudder distance is over 18" turns on a dime thanks to Racey:thumbsup

[vdcruiser]

With the rudder that close to the transom and no cav. plate above it, it may be pulling air from the surface of the water and causing the rudder to cavitate or operate in a pocket of air.

[AzGeo]

IMHO it's the balance of the mass and the position of the prop itself. The boat was built to run without plates (save money) and the faster you go, the less steering control you will have.(bow steer) IMHO you need to move the prop forward (cut the strut and shaft) and move the motor back as far as you can. THEN you will need plates, a turn fin, and realize some much needed speed. In other words, the bulk of the gross weight FALLS FORWARD at speed because the motor is too far forward and the prop is too far back, and lifts the tail under power. When I worked with/custom rigged boats for Howard Brown, he had two positions for the struts on his cruisers (both Spectra designs) The original position that required no plates, and the other position 6 inches forward of the first, for boats that ran more power and required plates. I offered these simple (low cost) changes here first, instead of just telling this guy to 'bring me the boat and $13K to re-rig it with good hardware' (not bronze stuff) or just send it to one of the 'self proclaimed artitsts around here' and spend $25K, for the same performance. I hope my opinion on this subject is now more clear. IMHO this boat was originally built 'as a budget V-drive' and it can be corrected for a reasonable amount of money. I am sure there are a number of different ways to do this job, what I have offered has worked for me (and my customers) for over 40 years. "That's it".

[Its good to be King]

WHAT THE FFFFFFFFFF . ???????????????

[specrocz]

My engine couldn't move much further back, the exhaust hoses are about 12" and the balancer has about 5" to the rudder. Maybe the hull has a hook to it and it wouldn't plant the bow so fast and so much if it were to be removed. It does plane very quickly and gets to speed in a hurry. If I were to move the strut forward, would it have to be a new strut or could the existing one be used? Another thing the Moeller poly fuel tanks I installed 10 years ago put the weight of the fuel near the filler cap. I have a pair of Imco aluminum 24 gallon tanks to put in which will bring the fuel weight to the rear where it belongs.

[74 spectra20 v-drive]

That 24 is a heavy boat with a lot of bow out front not sure how much impact plates would have if any without major power and running gear mods. I have a friend with a 20, it has decent power and running up about 45mph there is little to no change with full up and full down plates, this boat was a coast guard boat as well and is a heavy mother, I would put money down that it weighs close to what the standard 24's weigh. This boat has original strut locations and angels prop is close to 3" from the bottom of the boat.
Vdrive cruiser on these pages has a Howard 20 with strut mods and a lot of HP, the mods he undertoook made a world of difference to his boat, but again that is the 20 not the 24.
I moved the strut location added a long barrel strut with less angle and extended the inside lap strakes nearly 4' on my 20. It originally came with no plates and I was told that the 20's didn't need them unless you changed the power and added quite a bit to it. I was puting plates on it regardless. I personally love the look of the CAV plates, have been a flat bottom guy all my life so in my mind a vdrive with no plates just "looks" wrong. As I am getting around the day cruisers I am seeing that many really do not need plates to cruise and pull a skier.
I am still building my 20 so I do not have any comment on the performance mods, I also never drove the boat prior to tearing it down, just have the refrence of my friends boat and again it is a heavy beast.

[AzGeo]

It looks like you extended the 'center strakes' back to the strut area. GREAT MOVE !!! That is what will hold all that gross weight up while you are pushing it forward with an 8 degree strut. Mount the water pickups (aprox) 14" ahead of the prop (2" ahead of the strut base) and you will have no cooling problems. One for motor cooling and the other for trans and V-drive cooling. When my shop did 'custom rigging' for Howard Brown we always tilted the (20' and 24') hulls 90 degrees and never turned them over as you have done. So you moved the strut (forward) and sharpened the keel. (nice work) IMHO you will ride on those extended center strakes (with the 8 degree shaft angle) to about 110/115 MPH. IMHO great work !