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Message |
    
Adrian Watkins
New member
Username: easydiver
Post Number: 1
Registered: 12-2009
| | Posted on Monday, December 14, 2009 - 05:48 am: | 
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hi all, newbie here, just bought a 1995 20ft fletcher with a 5.7 350 magnum mercruiser in it, does anyone know which version engine this is, and HP, and whats the best prop to use, for calm sea conditions, im a novice where it comes to boats, any help would be apreciated,
Many thanks
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Brian Brackett
Senior Member
Username: kainon
Post Number: 1081
Registered: 03-2009
| | Posted on Monday, December 14, 2009 - 09:10 am: |
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Best to look at the serial number and look it up, I like dougrussell.com for parts pictures.. typically 260hp, the best prop is what ever works best for the weight of the boat with passengers and gear. there is no 1 that's best a 21p SS could work great till you have 8 people on board.. then you'll need a 19p.. 4 blade grips the road well, but takes 100rpms of the top.. you need to take the boat for a ride and watch the Engine RPM/TACH Gauge.. that's the most important ( for knowing engine performance ).. a GPS Speedo either handheld GPS (phone or GPS Map thingy) or Chartplotter. |
Kghost
Senior Member
Username: kghost
Post Number: 1152
Registered: 07-2008
| | Posted on Monday, December 14, 2009 - 10:03 am: |
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That is a Vortec 350 cubic inch chevy motor (marine). A standard 5.7 is 260 hp, a 5.7 (350) magnum is a 270 - 280 hp,
Typically most boats as yours would run a 17 to 21 pitch prop.
But the issue is to reach max rpms when at full throttle and trimmed out, 4400-4800 rpms.
That is normally how to chose the correct prop pitch. Once you know this you can decide what type of prop to use, stainless steel, 4 blade or 3 blade etc. etc. |
Adrian Watkins
New member
Username: easydiver
Post Number: 2
Registered: 12-2009
| | Posted on Monday, December 14, 2009 - 10:40 am: |
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Hi, Thanks for the swift reply guys, havent got round to getting it on the water yet, im chuffed with the engine ID though,
Thanks again for the info |
Kghost
Senior Member
Username: kghost
Post Number: 1153
Registered: 07-2008
| | Posted on Monday, December 14, 2009 - 11:11 am: |
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There should be a METAL tag riveted to the block just above the starter. It has the engine serial number on it.
Also the transom and outdrive serial numbers should be very close to the engine serial number in sequence. Of course that is if it is all original. |
chiefalen
Advanced Member
Username: chiefalen
Post Number: 454
Registered: 03-2008
| | Posted on Monday, December 14, 2009 - 05:27 pm: |
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Sweet motor take care of it and it will take care of you. |
Bob Griest
Member
Username: hippie
Post Number: 95
Registered: 04-2009
| | Posted on Saturday, January 09, 2010 - 06:19 pm: |
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I'm impressed!! That is the first engine that has it's hoses runnung correctly. Bob |
Ricardo E.
Advanced Member
Username: ricardomarine_vp
Post Number: 912
Registered: 03-2009
| | Posted on Sunday, January 10, 2010 - 09:02 am: |
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Adrian , If I may...... your propeller selection is determined by using the WOT RPM test. And we don't shoot for MAX RPM, we shoot for the WOT RPM specified by the OEM and IN the OEM manual for your specific engine!
This is to be a test ONLY to determine if the over-all gear ratio and propeller are correct!
a.) engine must be in near perfect tune.
b.) hull must be clean.
c.) drive must be clean.
d.) prop must be in tune.
e.) load the hull for how you anticipate using the boat! (You may very well end up with several propellers...... one for each type of usage/load)
The above must be satisfied before a WOT RPM test will render any accurate and/or positive results.
Example ONLY: if YOUR WOT RPM is to be 4,800, then you must be able to reach this rpm for the load you will be using.
If you cannot reach this rpm, then the propeller pitch (and/or size) must be reduced.
This prevents us from Over-Burdening the engine at all rpm range.... particularly the "cruise" rpm.
If you can exceed this WOT RPM, then you may pitch UP!
(best to ERROR on the side of a high WOT RPM rather than a Low WOT RPM...., IMO)
NOTE: Once prop selection has been determined, WOT RPM is not to be considered a sustained RPM! (spelled premature engine wear/failure)
You will eventually figure out where your "cruise" rpm and hull speed should/will be!
Now your engine will have a better chance at living a long life!
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