1994 mercury 40hp 4 cylinder 2 cycle

skiff00

Cadet
Joined
Nov 13, 2016
Messages
9
Does anyone know what prop fits 1994 Mercury 40hp model 0g012319? It appears the prop on my motor is too small, not enough numbers on prop to identify what is on there. Need correct diameter, prop pitch, it is a 13 spline prop, any help appreciated, Thanks
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
Welcome to Iboats,

If no info is available, remove prop and take it to a prop shop and have it measured. The only way to know if prop is too small or not opt for that combo is with a tach. OB needs to run middle to max wot rpm rpm as usually loaded, then can go for a prop maximization if needed.

Happy Boating
 

skiff00

Cadet
Joined
Nov 13, 2016
Messages
9
Thank you, I have looked through available parts list, but part number is not available. The old prop appears to be a michigan wheel, starting numbers 03
 

Sea Rider

Supreme Mariner
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Sep 20, 2008
Messages
12,345
A prop shop probably won't know prop brand, but will definitely tell diam and pitch. Chech that before going for a wot spin, will know if current prop suits or not your boating application and load. Can go from there maximizing other more or less prop pitch.

Happy Boating
 

fishin98

Chief Petty Officer
Joined
Nov 28, 2009
Messages
521
Just go up to the boat propeller section here in Iboats and you will find the right prop....what kind of boat are you dealing with? weight and length will determine what pitch prop to order.
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
That engine has a 1.83:1 lower unit gear ratio. It was typically fitted with a 10-1/4 diameter and 13" pitch. If this is on a light weight boat that prop would likely work fine.
 

skiff00

Cadet
Joined
Nov 13, 2016
Messages
9
Which prop would you recommend, a 3 blade or 4 blade for overall performance?
 

Silvertip

Supreme Mariner
Joined
Sep 22, 2003
Messages
28,758
Depends on what "performance" you have currently and what you want to correct. Outboards don't have transmissions like a car so the prop must get the boat out of the hole, up on plane and then provide engine rpm at or near the top of the manufacturers recommended wide open throttle rpm on whatever boat the engine is mounted on. So one size definitely does not fit all. You use less pitch for hole shot at cost of top end speed. You "may" be able to increase top end speed with more pitch provided the engine can twist that extra pitch. So the long and short of this is that three blades are best all around. Four blade if you have hole shot problems but they are not as fast. On that engine aluminum is fine but stainless "looks fast". Depending on how the boat is "typically" loaded you may need to go down an inch in pitch. My fishing buddy has a 50 HP version of your motor and 13P three blade works fine on his 16.5' Lund. You need to run your boat wide open with what you consider an average load (the way you typically load the boat with people and gear). Note the engine rpm and speed. Use gps speed for better accuracy. If the engine is lugging, you need to step down in pitch from what you have now. If it is at or even a bit over the top of the rpm range you can step up in pitch. Your old prop can be measured by a prop shop to determine it's pitch. But without some numbers to compare you are in a crap shoot when it comes to prop selection.
 

Sea Rider

Supreme Mariner
Joined
Sep 20, 2008
Messages
12,345
The right prop form is only achievable under trial and errror with a tach on a wot spin as currently loaded on flat calm no wind water cond while engine achieves middle to max wot revs factory stated. Doesn't matter if it's a SS, Alum 3-4 blade prop. Blind, wild guess prop suggestions, recommendations can turn into a costly experimentation with no avail to suit spot on your boating requirements as each combo is unique.

Going for other props is dumping money into the deep blue when you have not tested current prop to know what you need to correct or better.

Happy Boating
 
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