Slow top speed on Tomcat

P

pwsuser

New member
Hi,

I am buying a used 2006 Tomcat with 135 hp Hondas with about 300 hours. The boat has sat in the water since new with antifouling paint. The boat has been taken care of very well. The top speed is 25 kts, everything I have read here is that other Tomcats with 135 hp Hondas have a top speed of about 35 kts or more. I had the motors looked at by a mechanic, they are sound. Top rpm are about 5600 with 15x17 aluminum props.

My concern is why the slow top speed, my big concern would be if there has been water intrusion into the hulls and they are waterlogged, but I have seen almost nothing about Tomcats or any C-Dory getting a waterlogged hull.

From reading the forums here it seems that likely candidates for lowering the top end are: Aluminum props (it has those), old gas (it has that), ethanol gas (it has that), growth on hull (need to check when pull it out of water), too much weight on board (not an Issue), wrong motor height (they seem fine). So how likely is it that there is water intrusion? Did they build some of the 2006's heavier than others?

Any advice would be appreciated.

PWSUSER
 
pwsuser":2tjwgq3x said:
Hi,

I am buying a used 2006 Tomcat with 135 hp Hondas with about 300 hours. The boat has sat in the water since new with antifouling paint. The boat has been taken care of very well. The top speed is 25 kts, everything I have read here is that other Tomcats with 135 hp Hondas have a top speed of about 35 kts or more. I had the motors looked at by a mechanic, they are sound. Top rpm are about 5600 with 15x17 aluminum props.

My concern is why the slow top speed, my big concern would be if there has been water intrusion into the hulls and they are waterlogged, but I have seen almost nothing about Tomcats or any C-Dory getting a waterlogged hull.

From reading the forums here it seems that likely candidates for lowering the top end are: Aluminum props (it has those), old gas (it has that), ethanol gas (it has that), growth on hull (need to check when pull it out of water), too much weight on board (not an Issue), wrong motor height (they seem fine). So how likely is it that there is water intrusion? Did they build some of the 2006's heavier than others?

Any advice would be appreciated.

PWSUSER
Click to expand...
I doubt seriously that there is a water intrusion problem. With twin 135's you should get closer to 32-35kts depending on load. I'd bet more growth on the bottom (you didn't indicate if the bottom has been repainted multiple times since new), prop or engine problems. If the mechanic thinks the engines are sound, that would leave prop or growth as the more likely culprits.
 
I would definitely check the bottom. I keep my CD-25 in the water year round here in Annapolis and even though the bottom is painted it will become fouled when sitting. Performance can drop by as much as 10 knots. My top speed is ~30 knots when the bottom is just painted and as low as 20 knots when the bottom is fouled.

I re-paint the bottom every 2 years and in the interim take the boat to shallow water and scrape/scrub the bottom. Because the bottom is painted most everything comes off easily. I know it is time to clean the bottom when my top speed drops significantly.

I hope this helps.

Thanks, Dick
 
There should be no more water intrusion in a Tom Cat than any boat kept in the water. What one worries about is saturation of the core. I am not positive if the 2006 had foam, or Balsa. The thru hulls were already in place from the factory. The transom was foam core. The only point for water intrusion would be raw water intake on the port hull. It would be a stretch to get any water intrusion in the hull bottoms from the bracket or scuppers. It would have been a good idea to put an epoxy barrier coat on before bottom paint. If there is no osmosis (blistering under the gel coat--and into the first layer of laminate), then it should be OK.

I am not sure how much foam is in the hulls, this could be an issue--as it is in some cats. The issue is that there is no way to get water out of foam to the back. where the bilge pumps are. You can access the hull bottoms thru the water tank access, and the forward end of the galley, front of the fuel tank. My boat had the water tank on Stb--shortly after (May 2006 was the build date) they put the water tank on the port side.

My boat with Suzuki 150's hat a top end in the high 40's when the boat was light. When I sold the boat the top end was still in the mid 40's--about 45, as I recollect, and that was with 3 extra batteries (total of 6 group 31), freezer, air conditioner, extra chain, anchors etc.

The weight of the hulls and structure should be within a few lbs--no reason for a thicker layup.

The numbers suggest that you are getting a lot of prop slip, and the most likely cause is a fouled bottom. I certainly would put in new fuel, and get rid of what fuel is on board. The SS props would give you a couple of knots more, and are worth it for that particular type of boat.

Definitely go forward and have the boat hauled. Unfortunately a moisture meter will be of no value. Bottom paint, & recent haul out will all cause a wet reading. If you let the boat dry a week , then it will be of value. I would still look for blisters.

http://www.yachtsurvey.com/moisture_meters.htm

Just having bottom paint alone, would not drop the speed anymore than a knot or so. Between the old gas, the props, and clean bottom paint, it might give you a couple of knots. That you get WOT of 5600 makes me think that the engine is running fine. I would stick with the same pitch with SS props.

Great boats!
 
I'd think a bottom cleaning job and then a speed re-check would be first in order.

Then, if you still seem slow, and the motor performance remains the same (good), I'd take the boat out of the water and weigh it.

Most probably it's just got growth on the hull. It doesn't take much to knock a lot off the top end of your speed potential. Just slime, no barnacles required.

Joe. :teeth :thup
 
Hi Everyone,

Thanks so much for sharing your knowledge, as everyone says, this is a great website!! I feel much better now about the boat.

To reply to the speed measurement type question, it was measured with a garmin GPS.
 
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