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Message |
    
Patrick Brown
Member
Username: waternut
Post Number: 11
Registered: 11-2008
| | Posted on Monday, January 04, 2010 - 05:00 pm: | 
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I recently purchased a used 20' 06 Sea Fox CC that came with a Suzuki 115 4-stroke and aluminum 3 blade 14 X 19 prop that has a few very slight dings on 2 blades. I estimate the boat, motor, equipment and 2 passengers at 3000 pounds or so. I seem to easily over rev the engine-pushing the throttle down I can hit 6000 rpm no problem and very well could go higher. I get on plane quickly but do not seem to have good "top speed" with just myself and 1 other on board. Not sure what my speed is as my speedometer does not work and do not have an onboard GPS but I have followed a friends larger boat with a 150 HP 2-stroke and could not keep up with them and they had more people on board. I am considering a higher pitch prop like Michigan Wheels Ballistic Stainless Steel 13 1/8 X 21 model. Any other recommendations or opinions? Thanks in advance for all comments, I appreciate it. This will be my first prop purchase and am very leery of the whole deal. |
Cliff Casavant
Advanced Member
Username: chickenfry
Post Number: 248
Registered: 05-2009
| | Posted on Tuesday, January 05, 2010 - 11:49 am: |
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Can the motor be raised and or lowered remotely?
I feel that something else may be contributing to your over revving.
it would be nice to know your accrual speed do you have a gps from your car you could use??
i also would think that your pitch is close to what you would want now but your symptoms are strange do you trust your tach? |
Patrick Brown
Member
Username: waternut
Post Number: 13
Registered: 11-2008
| | Posted on Tuesday, January 05, 2010 - 12:56 pm: |
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Yes, the motor can be trimmed up or down at the helm. I typically have it trimmed up as we run in fairly shallow water at times. I do have a handheld GPS and can check the speed next time we launch...it seemed to me we were cruising pretty quick but I was very concerned about the tach climbing up as I advanced throttle to try to keep up with our friends-I kept thinking about the slightly dinged alum prop and wondered if we would achieve better performance with a stainless steeel prop. It seems the tach works fine but who knows? |
Cliff Casavant
Advanced Member
Username: chickenfry
Post Number: 249
Registered: 05-2009
| | Posted on Tuesday, January 05, 2010 - 01:13 pm: |
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well OK their are a few things here first their will not me a great performance difference between stainless and aluminum BUT what is important is the aluminum will give if you hit something in the shallow water where stainless wont possibly cosing harm for your internal parts.
second try trimming it down and see if your bite in the water is any better. I am inclined to think your caveatting also when on the trailer and your motor is trimmed down the cavitaion plate should be around flush with the bottom of the boat. |
Patrick Brown
Member
Username: waternut
Post Number: 14
Registered: 11-2008
| | Posted on Tuesday, January 05, 2010 - 02:01 pm: |
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Well, you may have just changed my mind about switching to a ss prop. This boat will be used both offshore as well as running up on plane hard through shallow areas to get to deeper water....so maybe a new aluminum prop would be better considering the "shock absorbing" ability of aluminum vs steel. The concern I currently have with the prop is it slightly dinged on 2 out of 3 blades. I also feel tach is probably accurate but am guessing at this one. I also understand I could get the current prop reconditioned but my gut feeling is to get a new prop and keep the other as a spare. I did trim it down a bit here or there but not enough I guess to notice much of a difference..I was primarily concerned about the water depth so therefore kept it trimmed up. I will check the trim down cavitation plate as it should be flush with the boat bottom. |
JUST-IN-TIME
Senior Member
Username: justintime
Post Number: 7315
Registered: 09-2006
| | Posted on Tuesday, January 05, 2010 - 07:00 pm: |
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i bet you got a spun prop |
hhenault
New member
Username: hhenault
Post Number: 1
Registered: 02-2010
| | Posted on Monday, February 15, 2010 - 05:29 am: |
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with a DF115 on a 3000 lb boat, the speed should be around 30 kn @6000 rpm, provided you have the good prop.
AFAIK, alu. 14 x 19, alu. 13.5 x 21, S.S. 13 x 21 props are slightly equivalent, which make me think you still have a prop which fits the boat and the motor.
if you think you are not at top speed even when trimmed up, check that the cavitation plate is aligned with the bottom of the transom, ( or slightly higher), and no closer perturbances (speedo, transducer ...).
In my opinion, the overall weight is under-estimated :
SeeFox 20 CC's Dry weight (2300lb) + motor weight (> 400 lb) + fuel (300-400 lb) + 2 persons + gear ... would be around 3500 lb, and top speed around 28 kn.
I had a 7000 lb boat powered by a DF115, and top speed was 18 kn (picture below).
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