New TomCat 25

Brent,

So glad to hear about your trip and that your boat is performing up to specs! On the water being thrown from one engine to the other, sounds possibly like same problem I had after the dealer installed both about 2 1/2" below the bottom planing surface of the boat. The anti-ventilation plate should be even to about 1/8" below the bottom of the boat as you know, at least on the monohulls. With the engines mounted 2 1/2" lower, they were throwing water all over the place during my breakin runs on Lake Cachuma (Roger took pictures!).

Thanks for the report.

Steve
 
Based on what I have read, I would think that one of the advantages of bracket-mounted outboards is that the outboard could be raised fairly significantly. The water flow that leaves the bottom of the hull curls back up towards the surface and the bracket-mounted outboard is running in that higher water, and can be mounted higher. The higher the outboard, the less drag. I wouldn't be too surprised if the anti-ventilation plate could be 1 to 2 inches above the bottom of the hull, but on the other hand, I'm no expert and can't say for sure.

Jim
 
Steve and Hoop,

Thanks for the reply's. The motors are mounted as high on the Armstrong brackets as possible now. Already in the highest hole. There is room to move the Armstrong brackets up another 3" to 4", but that would involve patching and redrilling 30 or 40 bolt holes. Not something I want to do on a new boat. I will contact Jeff Messmer and Scott Mathews at the factory to see if any of the other TC255 boats have had the same problems.

Really had a great trip on Lake Powell. Spent 8 days, fishing, cruising and just laying around. This is so much more boat than the TC24 we had previously. Went about 100 miles on the water. Launched at Bullfrog Marina, went uplake to almost the old Hite Marina. That's the end of the lake now, where the Colorado River pours in. Caught Large Mouth Bass, Small Mouth Bass, Black Crappie, and Walleye. Mostly plugging the shore from the dingy. Trolled some for Striped Bass but with no success.

Brent
 
Hi, Brent

Sounds like a great trip!

I have the opposite situation with my engines: My port sprays onto my stb, but not when she's above about 4100. I've got to finish the documentation process before I take her out again, and I'll also have the 15x19 props on then. I've never flooded out an engine.

Stopping at the exhaust fab shop today to check on progress for the compressor.

Reseated the rail flanges just in time for an inch of rain.

Bob Cat
 
Thought I'd pass along some information pertaining to the brackets for those of you that are curious about such things.

While it's true that when mounted directly to the transom the motor's anti-ventilation plate should be very close to the same height as the low point on the transom (this varies somewhat with hull shape) when mounted on a bracket the rule-of-thumb is that the motor goes up 1" for every foot it's back from the transom.

This works well on the deep-v hulls that brackets are typically mounted on but doesn't have direct application on a catamaran hull. A bracket on a deep-v hull acts as flotation for the motor at rest, as a giant trim tab when accelerating to a plane and then mostly lifts from the water once on a full plane. A catamaran hull does not have the same acceleration characteristics (it doesn't have as much bow rise and it doesn't lift as high when on plane) and therefor the brackets don't work the same way. As soon as the boat slows down and settles the rear corners of the brackets press into the water and become their own miniature boats with a wake and spray pattern.

Another issue with a catamaran hull with regard to spray is that there are two times more transom ends; that is, each hull has a transom and like all boats there's a spray pattern off the aft corners (in this case the brackets). Since the cat has two inside corners (and a converging wake in the middle) things get a little interesting; especially as the boat is slowed down and the transom settles further into the water. The Tomcat runs very flat at speed; as the speed increases the hull flattens and the pressure builds up in the tunnel which lifts the boat a bit along with the normal lift generated by the hulls. When this happens the spray at the transom subsides because the brackets ends are running clear and the spray off the transom is flat enough that it doesn't kick up over the engines. As the speed comes down and the stern settles the spray pattern angles up at the same time the transom angle is increasing (in other words, the angle is "closing up") and the intensity of the spray increases because the transom corners are digging deeper. The result is lots of spray being thrown up in the air and toward the engines.

This exact same thing happens on a deep-v monohull with an outboards on a bracket. The difference is that there isn't another engine next to it that's taking all the spray because the "V" shape of the hull and the bracket throw the spray out to the sides. Again neither engine ends up taking spray from the other; however, there's always a transition speed where lots of water is shooting up past the engines. It's a characteristic of bracket configurations and as an operator one just learns to avoid the speeds where it's the worst.

Think of it this way...with a catamaran you basically have two boats running side-by-side. If you were to take two individual boats out and run them as close together as the cat hulls are you'd certainly expect the aft end of each to get doused by the wake/spray from the other boat; especially at those speeds where there is lots of spray. Since the spray pattern off the transom of a boat is generally back and out the further aft you place the engine from the transom the more likely it is that the engine will end up in the spray pattern of the other hull. That's essentially the situation on the TC255; it's the result of the characteristics of catamaran hulls combined with the characteristics of the brackets. Essentially the solution is the same one employed on monohulls with brackets; you avoid the speeds where it's the worst. You either need to be up on a full flat plane where the spray is reduced (and flat) or slow enough that the hull settles and spray is not an issue. The in-between is sort of no-man's-land as it is on deep-v monohulls.

There's no doubt that raising or lowering the engine will affect how much spray is generated because the height affects the running attitude of the boat. The lower you mount the engine the more bow rise you get and conversely the higher the engine the flatter you can run with less drag, at least until the point where the prop ventilates. Tucking the engines all the way in tends to lessens the spray (at slower speeds when the hull isn't running flat) because the thrust from the props then lifts the stern which it turn means the aft bracket corners aren't depressed as much and that knocks down some spray. And, if you go too deep you create spray off the leading edge of the lower unit. But...height adjustments alone will not eliminate spray.

Something else that might help would be a spray apron off the rear trailing edge of the bracket (I'd go full width). I'd make it of some relatively stiff but still flexible material (white semi-truck mud flaps?) and make sure it reaches to the leading edge of the engine's lower unit when it's trimmed to its normal running angle. Th goal here would be to eliminate any spary being generated off the leading edge of the engine's lower unit as opposed to the spray off the trailing edges

Creating lift in the stern is a key component in reducing spray and reducing the running angle. I found on the original Tomcat 24 that the installation of the Honda SST hydrofoils (larger than Doel-Fins) made a big difference in trimming the boat. I haven't had the opportunity to try them on the TC255 but given there's no convenient way to install trim tabs this would be the next best thing.
 
I talked to Jeff and Scott from the factory yesterday. Seems the spray problem is only associated with boats equiped with Honda motors. Honda's have two extra small cavitation plates, above the main cavitation plate. These two small ones are picking up the water coming off the Armstrong brackets, and throwing it into the air. No problems on any boats sporting other brands of motors. We are working on some ideas to remedy the problem. Will report back with results later.

Brent
 
We received our 255 TomCat a few weeks ago here in Deltaville, VA. We have Suzuki 115 hp four strokes. They are 2001 engines with low hours swapped off the boat we traded in. We have an issue with water pouring up over the hydraulic steering arms and splashing up on the lower part of the engine covers when moving between about 8-12 knots. As soon as the boat is on plane, everything is fine. Same problem occurs when coming off plane. We have the boat at a local Suzuki dealer right now to get the engines raised up 2 notches (could go up 3, but worried about cavitation). I wouldn't describe our issue as water "spraying" on the engines, more like pouring up around the Armstrong brackets. Hopefully raising the engines will help somewhat, but I imagine the issue will still exist to some degree.

We love the boat, of course, and have only experienced one other problem. I found a screw protruding about 1/16 of an inch through the gel coat in the bottom of the port sponson about 8 1/2 feet from the transom. I noticed it only because of the small chip in the gel coat created by the screw. The Suzuki dealer is also fixing this.

Thanks to all for the useful and entertaining information we have absorbed from this site in the past months. Haven't had anything to add until now.

Brock
 
Hi Brock. Sure would like to see that new TC 255 on the water. Would you like to meet up at Reedville for lunch some weekend? We're around the "corner" on the Potomac near Lewisetta on Cod Creek.

Would you consider coming to the Langford Bay Gathering in June? We'd love to see a 255 there, I guarantee you'd be the only one and the center of attention!!

Charlie
 
Posted a couple of pictures on page 6 of Dive Cat's album.

She has her name now.

And I added an anchor stop between the roller and winch. Just barely fit. I raised it 1" on a stainless block to align it. 2 x 3/8 machine screws go into a 3 1/2 x 5, 1/4" stainless backup plate.

Next is a couple of 6 x 24 drawers under the table.

Still waiting for the compressor exhaust system.

Pulled the boat 2 days ago. Had about 3' between my back tires and the water. Easily drove the boat up and stopped her about 1' from the ugly black rollers. Pulled up to level ground. Winched in low but she wouldn't budge. So I set the brakes to engage hard and fast, drove about 50' and slammed them on. Perfect! She came forward and just kissed the rollers. Unfortunately, there's still about 3" hanging over the back. Also, my safety chain is now too short to connect.

CD is supposed to be sending low friction material to recover the carpet. I can see what else needs to be done so I'll do it myself.

Bob Cat
 
Talked to Jeff M. at the factory today. After measuring our boat and comparing it to one they are currently testing, it seems our Armstrong brackets are 2 1/2" to 3" too low. That is responsible for the spray from one motor to the other. Changes the dynamics of the water flow coming off the sponsons, onto the Armstrong brackets and ultimately onto the motors. We will have the brackets changed in June when we travel to the North West. Already had a trip planned to do either Vancouver Island or on to S.E. Alaska, for June and July. Will just have to live with the spray at Lake Powell and the Delta/Bay Extravaganza.

Brent
 
http://www.boattest.com/index.aspx

Tomcat 255 video and evaluation is at boattest.com . The video was fun to watch! A performance chart estimates 3.2 mpg at 20.5 mph with twin Honda 150s, if I am reading it correctly.

Select C-Dory under manufacturers. I was not able to link directly to the specific web page.
 
Based on my real life experience thus far, I have seen a maximum of about 2.3 nm/gal with my load. Haven't tried the new props yet. Would love to see anything over 3.0!

Bob Cat
 
Bob Cat":3frffuew said:
Posted a couple of pictures on page 6 of Dive Cat's album.
She has her name now.
Bob Cat
Click to expand...

Bob, great job on how you incorporated the "divers down flag" within your vessel's name!
 
Just got my May 2006 issue of Motor Boating in the mail yesterday. They did a test drive on the Tomcat 255 on page 38. Different writer on the article than the one on BoatTest. Will be interesting to compare the two write ups.

Jack
 
New pictures on P. 6 of album.

This is the new exhaust pipe. A TIG welders dream! 316 ss with 321 ss bellows they call "wrinkle belly". The system flanges to the exhaust manifold, replacing the muffler. Up 7", across and down to the 1/4" raw water injection at about 3 gpm. Carried down hill to the same hull penetration as before.

All I lack is the Honda header gasket I forgot to order until today.

So, the question some may be hesitant to ask: How much?

About $500, including the space age silicon/fiberglass wrap that covers the "hot" section prior to injection.

Result: Absolutely no heat in the transom and a more efficient engine from reduced exhaust backpressure from the muffler removal.

We were out Wednesday with the new props. We left the data on the boat so it will be reported over the weekend. Mileage did not improve, but WOT was reduced to 5500, the minimum. More later.

Bob Cat
 
Katy and I spent our first night on Dive Cat . . . in the parking lot at the Channel Islands ramp! Great practice and a lot of fun. Felt a little vulnerable to wandering land sharks who might have an interest in boarding so we had non lethal as well as lethal repellant.

Launched Sunday morning for Anacapa, then on to Santa Cruz with the original props back on (14 1/4 x 17). WOT back to about 6k and 35 kts. Best economy at 4200, 24 kts, 2.1 nmpg. Full fuel, water, 2 pob.

Compressor works great. Watermaker produces. Invertor works. Generator has to be connected to a bonded ground so the invertor will accept the power.

Back to C.I. next week for installation of curtains and cushions (like Fishtales) and measurements for a cockpit cover later on.

Launch and recovery process continues to improve. Still need a better roller stop on the trailer.

Going to San Diego/Chula Vista May 13-14 for granddaughters 1st b-day and rides in the beautiful bay. Visitors welcome!

Bob Cat
 
Bob,

You sure were lookin' good in the parking lot.
April23_2006_022.sized.jpg


Photo taken mid-day on Sun.
 
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