Motor size for Tom Cat

[onwater4fun]

We will be buying a Tom Cat and would like suggestions or experience input with regard to motor size. We do not fish but cruise long distance 95% of the time at 6-7MPH. We would like to equip our Cat with motors that would offer good economy while putting but would be powerful enough to cruise on plane when necessary.

[thataway]

I would not consider the Tom Cat 255 as a boat for long distance cruising at 6 to 7 knots. My experience is because of the drag of the bridge deck being in the water, the mileage at 7 knots is the same as at about 24 knots. Also the Tom Cat needs to get up on a plane to be on top of the waves for the smooth ride.

The boat in the Chesapeake which I belive is still for sale, has used 115 Suzuki's--the 115's and 90's seem to work fine on the 24's. I feel that the 255 is a better boat with the 150's. The reason is that it is more responsive--when you have to drop down speed, it gets up on a plane a little quicker. I am sure that some will feel that 115 hp per side, is OK and many will vote for the 130's. However, the mileage seems to be about the same for 115 to 150's. (Don't know of any 175's--but suspect it would be similar with that power).

If you want the slow speed seriously consider the C Ranger tug 25.

[journey on]

Or a C-Dory 25. Runs well at 7 knots, and is 1/2 the price. Same size cabin as the Tom Cat, except for the v-berth.

Boris

[squidslayer]

I can keep on plane with my TomCat 255 as low as 8 -10kts with permatrims.... you can get just as good mpg at 15kts too..the 25 C-Dory is goes for 70 k.....the TomCat 100k but the TomCat is TWICE the Boat......
I went with 150 Hondas because they get about the same MPH as the 130 or less....its not how much horsepower you HAVE that is you MPG..its how much HP you USE to push x amount of weight
Plus Honda will finance your WHOLE BOAT including electonics..trailer...for 6% 15year

Dick
255 TomCat
ShirleyMae
Orinda

[drjohn71a]

As mentioned above, the hull shape has much more wetted surface at hull speeds than planing speeds, thus less efficient. However, Brent and Dixie on Discovery have used a single engine at slow speeds for cruising efficiently in smooth water (they have Honda 135's).

The Honda 150 pretty much behaves as a 135 until you get the rev's up. It is really nice to have that extra power when storms are nearing, or have already caught up with you.

I have 150's and feel that's the best available at the time.

However..... with the TomCat's sensitivity to aft weight, if they were available, I'd be looking really close that the new Evinrude E-Teks.... they are hundreds of pounds lighter than the four strokes and no break-in, no 20 hour maintenance, no 200 hour maintenance.... That would be nice.

John

[JimD]

The difference between a Honda 150 and an E-Tec 150 is only 59 lbs (20") or 58 lbs (25") So times 2 it is 118 or 116 lbs..I guess significant on a stern sensitive tomcat. (the weight issue gets very noticable when comparing to the Verado) The big weight to power ratio occurs when using twins on a non cat. For example, when using 2 Hondas to achieve a total of 150 hp @ 384 lbs ea. for a total weight of 768 lbs vs a single 150 @ 478 lbs. Now THAT is significant! Lower mpg too. Of course the peace of mind and slight mauverability (they are closer together than say on a tomcat which REALLY gains low speed manuverability from 2 engines) increase are the tradeoff.
My offshore buddies tell me that low end torque on a 4 stroke make riding the throttle in large swells almost a thing of the past, whereas it is a must on a 2 stroke.
Having said that, I am a 2 stroke geek all the way, having had 2s all the way back to the 60's and seen them hold up as long as 40 years with minimal maint.

[drjohn71a]

Jim -

I had not realized there was such a small weight difference on the Honda/E Tek comparison. You imply that the Verado is different. Is the Verado heavier?

John

[JimD]

[JimD]

[thataway]

My experience with low speeds is if one goes much over 6 to 7 knots, there is a fair amount of drag and turning effect of the single motor.

Some what contradictory is that although the widely spaced motors of the Tom Cat should give much more maneuverablility, the "keel" effect of the two narrow hulls tends to resist turning, so one has to use a fair amount of power to manuever with just the twins (not using changing direction of the props by steering)--so I tend to steer as I do with a single motor. The effect of twins seems much more with inboards than with the two outboards of the Tom Cat.

Good question if one put a much lighter engine on the boat if the bridge deck would be clear of the water. My neighbor has a TC 24 and his bridge deck also drags with twin 115 Yahamas, so I suspect that one would have to get well dtown in HP (weight) to get the tunnel clear aft. I haven't seen one of the Tom Cats with no engines. But if you wanted to run at only displacement speeds, than you could consider mounting only a single engine--that would get the weight way down--and with 25 to 40 hp you would get speeds of 7 knots or maybe a bit more with excellent economy....but then, you have lost the real feature of the Tom Cat--which is speed. (in my opinion).

I don't see the TC as being "twice the boat" as a CD 25--the TC does have a bigger bunk and I believe a bigger cockpit--but if one only wanted displacement speeds, the CD would be considerably cheaper with a small single engine....

[journey on]

As long as we're discussing Honda motors, let me try this one, an honest question. When we bought the CD-25, we were offered the Honda 135, but I went for the Honda 150.

Now these engines are both the same motor; as near as I can figure out it's the Accord 4 cyl set on end. Honda claims the difference in horsepower comes from "V-Tech" and Scott Reynolds claimed it's only good over 4000 rpm, a number I rarely see. Honda has never defined what V-Tech is, though they charge $850 for it.

I just read that on a motorcycle V-Tech lets the engine run on 2 valves/cyl at low rpm, and uses 4 valves over 4000 rpm. That wouldn't let an engine go from 135 to 150 hp but it might increase the bottom end torque.

Anyone know what V-Tech is on an outboard? I assume it's some change in the intake, but what exactly is it?

Boris

[JimD]

go here http://www.honda-marine.com/outboardprofessor.aspx# and choose "vtec" on the right column
If you rarely see 4000 rpm at wot then change your prop pitch. If you just cruise slowly then have fun!

[squidslayer]

TomCat's sensitivity to aft weight ?????
I have not noticed any ....if fact I think alittle more weight would help in the aft......I could trim the bow down a little for a change instead of negative and up.

Dick
"ShirleyMae"

[JimD]

[thataway]

I would not characterize the Tom Cat 255 has being sensitative to weight aft--it does with the 150 hp engines--but if you start adding more weight aft it may change the handling characteristics. The issue is that the tunnel is not open at low speeds--the boat has to be on a plane before the tunnel is open and air can pass thru. The cushion of air allows a pillow like affect. If the bridge deck is dragging (which it does) there is more resistance to progress thru the water, and there is more propensity to slap when you hit a wave. Many of the other cats have air under the bridge deck and the tunnel is open at displacment speeds, giving a better ride.

The trimming bow down brings the stern up and opens the tunnel, but only at planing speeds. We will have to so some photos at different speeds (from another boat)--to see at what speed exactly the tunnel opens up. I will be very surprised if it is open at 8 knots, even with the bow fully trimmed down. But I'll document what I find with photos--have friends from the PNW arriving tomarrow, and that will be a good oportunity to do some tests.