prop size

searaymerc

Cadet
Joined
Jul 5, 2014
Messages
10
I have a 1986 searay seville bowrider with a 120 up I'm running a 19 pitch prop and at wot I'm only running at speeds of 25 mph at 3200 rpm. The motor says that it should be turning between 4200 and 4800 rpm so I just don't think I'm getting everything I can out of my motor. Can the prop be the problem or do I have other problems
 

joetheis

Petty Officer 1st Class
Joined
Apr 21, 2014
Messages
308
When I first slipped my Silver Line with a V-8 (305) motor, in the water, alone in the boat, , she'd get on plane I thought pretty good, (first motorboat so I don't know HOW FAST it should get on plane)
with a 19" prop.
Later,
I had my wife, another couple, my 9.9 kicker engine, fuel, etc. on board.
She would not get above 3,000 RPM, or get on plane!!!???
My buddy told me I had "too much prop".
I went to a prop shop, told my sad tale and the guy sold me a 17" 3 blade prop.
Made a world of difference!!
The idea being that the bigger prop was making the engine "work too hard", (like a higher gear in a truck).
I looked at props myself before I went, figured I'd get the "OEM" size prop, (no! they are set up like that),
I was told some place will even let you try a prop before purchase!!
There is a pile of good info on line about props, (careful, some is too technical).
Joe
As always take any advice I give with a beer er 2!
 

mkfs9

Seaman
Joined
Jul 8, 2005
Messages
64
Sounds like the right prop size, something else going on here I think.what size boat ?. My Seville is 18 ft 175 HP runs a 21 p easy could prob push a 23p if not fully loaded ect.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Give the motor a physical , compression,note the condition of the plugs and their location.
Check that the timing is set right and advancing as it should.
Check that the throttle opens all the way.
At only 3200 and 25 mph I wonder if your missing a cylinder?
A healthy boat motor combination should approach about 35-37 mph.
Water sports would probably require a 17" prop.
 

searaymerc

Cadet
Joined
Jul 5, 2014
Messages
10
Thanks for all the advice I will try the compression test definitely and check timing advance what should it advance to
 

mkfs9

Seaman
Joined
Jul 8, 2005
Messages
64
I can get over 50 mph with my Seville 18 ft. 175 v6. On 21p laser11.1988 boat so its quite heavy.
 
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