ARE 200 hp Suzukis too much for the 255 Tomcat?

[pwsuser]

Hi Again,

I am thinking repowering my 2006 255 Tomcat with 175 hp or 200 hp Suzukis. I am mainly considering the 200hp because they are only 25 pounds, each, more than the 175 hp and they have the latest technology. I am thinking I may get better gas mileage if I keep my speed down. Also I generally go long distances with lots of weight.

I would like to know your thoughts on this issue.

Thanks,

Dave

[Aurelia]

Looks like they are the same basic motor/weight and I can think of at least one boat in our area that runs the 175s just fine. Motor weight is nearly identical. Is there a maximum HP rating for the Tomcat hull?

Greg

[pwsuser]

The Manual says 300 hp for 225 Tomcats.

Although I talked to my insurance agent and my bank and neither seemed to care if I went over the maximum rated hp.

[Reddog]

300 HP total? (150 x2?)
I am inclined to think that this issue has more to do with weight than thrust. The laws of hydrodynamics will limit speed (within reasonable limits). I doubt that in a real world overpowering would result in a transom failure. I go with if the weight is within the specs, more HP is fine.
I had a 69 Chevrolet with a built 454 that would break the tires loose in 4th if you nailed it, the solution was not to nail it.....

[gulfcoast john]

Hi Dave,
When you were buying your 2006 boat with Honda 135's this time last year, you posted that they had about 300 hours. With good maintainence you could get thousands (lots of regular use is better for outboards). Personally, I only know one TC255 owner who had 175 Suzuki's, Peter Brownell on Destiny II. That was a 2009 Marc Grove/Wefing's boat customized by Marc. Peter told me he never used or needed the extra power at Marc's Oct 2013 (or was it 2014?) Gathering. Beautiful boat. As I recall, they cruised from Lake Champlain to Florida areas, not Alaska. You want mileage? Brent on Discovery posted getting 4- 5mpg at under 2000RPM running one engine at a time in displacement mode with Honda 135's.
Some will claim you should never exceed the C-Dory twin 150HP rating for legal, liability, or common-sense reasons. Reasonable points.
I have a hard time imagining that twin 200HP engines at 3000RPM (likely its most efficient speed) would get better MPG than your 135 Hondas at 4400RPM (likely just before their MPG starts to soar, but a LOT less than twin 200's soars). I might be all wrong here, but I can't image twin 200hp engines getting better MPG than twin 135's ANYWHERE in the cruising RPM ranges of each.
The TC255 is a great boat, but I think it takes years and maybe hundreds of operating hours to get really familiar with it. I never need or use all the power of twin Yamaha 150's (but we're not in Alaska waters). Since there are lots of Honda 135 owners, and no 200HP owners posting, I'd advise saving those quite considerable bucks for a few years. I confess to posting about hanging Suzie 200's on that last new TC255 Marc got in, and he posted that he'd gladly do it, but that was pretty much in fun. So, if that's where you got this idea, forget it. I couldn't be happier with the performance of my boat (which, sadly, often functions as a floating RV base camp for weekend beach trips of 7-25 miles total until we retire next year). Compared to other RV's, the 255 is way more expensive, but floats better. At our 4th boating season after purchase, I still haven't decided which of 3 sets of props are best (I'll invest in a stainless version when I finally make up my mind, or maybe not). If I can take 4 years to decide on props at $118 each, you can take 4 years to decide on changing engines, and save some BIG money to boot. Or maybe not. Your call.
Happy Boating!
John

[Aurelia]

See the latter pages of the tread below for mpg numbers favoring the 200hp yamaha over the 150 honda on a 25 cruiser hull at similar rpms.

http://www.c-brats.com/viewtopic.php?t=23047&start=60&postdays=0&postorder=asc&highlight=

Greg

[pwsuser]

The rating of 300 hp is total for the Tomcat.

I bought the boat last year with about 300 hrs on the 135 Hondas and now they have 480 hrs, so I have been using it quite a bit. I was not happy with the gas mileage or cruising speed and have been working on that since I got the boat. I have changed many things and i have increased my speed and mileage.

However, I run very heavy sometimes and even when light I cannot cruise on step at lower RPMS like 3500 as some on here seem to be able to do. I have a flowmeter now so i can see how speed affects mileage. When I am light my best mileage is about 4000 RPM at about 20 knots, with medium weight, best mileage is about 4500 RPM at about 23 knots, when heavy, best mileage is amazingly at about 5000 RPM and about 26 knots. I interpret these results to mean that i am not fully on step and planning when heavy until 5000 RPM.

Do you agree?

Given that I generally run with medium weight and at 4500 rpm, seems like my motors are working plenty hard.

One of my 135hp Hondas has failed and needs a major rebuild, that is why I am considering repowering and getting larger motors.

[starcrafttom]

I would agree with what Greg is hinting at. People get the idea that more horse power means more fuel burn. And at full throttle they would be right. but Cdorys do not run at wot that much. I believe and have seen that running a bigger motor at lower rpm then a smaller motor at higher rpm result in better mpg. If you are running heavy and in heavy sea, In the PNW we are always running against current and wind, Then more power at a lower rpm is a good idea.

[T.R. Bauer]

I'm not convinced that high RPM = bad fuel consumption. I do understand that we take what auto engineers do with lowering rpm in a car and try apply this boats to accomplish better MPGs. Of course, this is possible if you can just loaf along like a trawler does. However, a boat is clearly not a car. It takes about 10-20 hp of the available power for many cars to cruise along at 60 mph. In a boat, like our C-Dory, one is often using 80-90% of the available power to maintain 20-30 mph. To keep weight down, small and light motors need to be spun up, sometimes a lot, to accomplish a nice power to weight ratio. I takes a lot of power to keep boats on step.

Anyway, I think you will see a difference with new motors as technology has come a long ways. I don't think it will be very large though - probably negligible. However, I do think you will be far happier with your boat, and that is what matters most.

[Aurelia]

Revolutions per minute need to be fueled so the more of them means more fuel used. Now that curve of more fuel with more RPMs is not the same from one brand motor to another but it is a constant on a given design.

The multivalve/injected programming of modern engines can surely have a larger motor using less fuel at 3k RPM than a smaller motor at 4k RPM.

Lots of variables make that possible and even likely with more programming factored into the fueling.

Greg

[rogerbum]

[Dreamer]

As I recall, a few years back, the max HP for the TC255 was raised to 350. That's when we started to see the 175 Suzukis used. My slogan has always been, "You can never have too much HorsePower" !

[thataway]

The 150, 175 and 200 are all the same block--2.867L, The difference is in the new head and higher compression . Supposedly the new 200A has "lean burn" technology, and will develop the high HP at the top end--probably in the 5000 to 6100 RPM range. You are going to have about the same performance down in the usual cruising range (remember the Suzuki swings a larger and higher pitched prop). The boats are planing at 15 knots. They run better in the 25 to 30 range.

One of my peeves with the Tom Cat, is that they put 135's on them to start with. I sea trailed a heavy boat with 135's and it was a dog.

My Tom Cat, when light would hit almost 50 mph. Even with full cruising load it would hit 46, and I often cruised a 35 mph. Several times I beat my wife home from Apalachicola--with her driving, and my on the water at 35 mph. (about 200 miles)

My usual cruise was in the 25 to 28 knot range, and in the mid to high 3K RPM range.

The Suzuki is MRSP is about $18,600. Some advertised price is in the $12,000 range, only a $1500 more than the 150. But, it is going to cost a bunch more in AK. Plus you now have to change out all of the engine rigging. My guess is that you are going to pay over $30,000 for the change out--maybe $40,000. Capt, Charlie had a Tom Cat with twin 115's (not too far from the Honda 135's), and sold that to buy my boat with 150's (plus air etc)--he felt it was cheaper to do that than reposer etc.

Only you can make the call about the cost and benefit. You may get slightly better fuel mileage, Are you getting 2 mpg now? if so, that is about as good as you are going to get with a heavy boat. Even 1.6 is not uncommon. OK--lets say you go to 2.1 miles per gallon or even 2.2 miles per gallon. How long will it take to get back the $ you spend for the upgrade? My guess that not in a number of years. The higher speed, may be worth it--but the ride in the heavily loaded boat is not as good as in the light boat.

In the Boat Test, with Honda 150's at 20 knots they got 2.8 miles per gallon. That is a number that none of us had gotten. They found 20 knots to be the most efficient planing speed, for that boat.

The boat should handle the souped up 150/200 hp Suzuki with no problems.

[gulfcoast john]

Dave,
Sorry about your premature Honda failure at under 500 hours. You didn't even mention that, although most Brats would have some livid rants here in that situation. How mellow. Even the Coast Guard guys seem to expect thousands of hours out of a Honda. Bob has many good points as always, including having to changeout the engine rigging (including gauges, which alone can be in the thousands with Yamahas). I also agree that a typical TC255 'expedition quality trailerable pocket yacht' as usually outfitted needs twin 150's, never 135's.
Even with my 150's, I'm not real happy with the 'feel' of the boat until 3900-4000 RPM and 23-25 MPH (not knots) getting 1.9-2.1 MPG combined, with my 4 blade cheapo 17p dinged aluminum props and a bottom which can get slimey in 1 week when the marina water is over 85 degrees like now. Ablative bottompaint works best with use, and our trips are short. You have a good case for engine replacement, including Rogerbum's comments (he has a wealth of experience far offshore fishing in heavy mode). If you decide it's worth it to hang 200HP twin Suzies, you'd be a trailblazer on this site. That alone is reason enough (hint, hint).
In any event, best of luck! It's a great boat!
John

[T.R. Bauer]