Omc electric shift prop pitch and size

Hi I am wondering what pitch and size prop I should be using I have a old school 1977 electric shift 351w 235hp pushing my 27ft boat. I understand this is a good size boat to get on plane quick with just a single engine. I now have a 14x14 size prop on it is this the stock size for this setup? I see different size pitch props online, I would like the boat to have more power outa the hole and not so much worried about top end being as we cruise about 20 mph anyways. I see they make a 14x12 pitch would that little bit help? Thanks much.

Re: Omc electric shift prop pitch and size

Thane2012 said:

Hi I am wondering what pitch and size prop I should be using I have a old school 1977 electric shift 351w 235hp pushing my 27ft boat. I understand this is a good size boat to get on plane quick with just a single engine. I now have a 14x14 size prop on it is this the stock size for this setup? I see different size pitch props online, I would like the boat to have more power outa the hole and not so much worried about top end being as we cruise about 20 mph anyways. I see they make a 14x12 pitch would that little bit help? Thanks much.

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Howdy,

This is really a Prop forum question. Maybe one of the MODS will move it for you!

You should size your prop so that the engine is turning at maximum recommended RPM at wide open throttle. (WOT)

This is assuming that the engine is in good repair, the boat is not overloaded (NOT waterlogged either) and has a relatively clean hull underside.

You must measure RPM with a KNOWN tachometer, have an accurate speedometer and it's nice to KNOW your drive ratio to make effective decisions on prop selection.

I am going to guess your 351 wants to turn 4400-4800 etc? If you know the range, select a prop that will give you top of range RPM with the boat loaded where you'll most likely operate (people, gear, fuel, stuff, etc)

If you're turning under the lower rpm in the range, either the engine is not tuned correctly, worn out, you're trimmed wrong, you're dragging an anchor, or the boat is over loaded etc.....


Regards,


Rick

Re: Omc electric shift prop pitch and size

Your OMC 351 with Model 14 drive needs to be propped to run within it's recommended rpm range(4000-4400 rpm) at full throttle.

You may be able to go down in pitch, based on where it's operating now. Expect to see 300-400 WOT rpm change between the available pitch sizes ( 12,14,16,18 ).

Lower pitch will result in better acceleration as long as you stay within the recommended rpm range.

Optimum set up would be to have it propped to turn nearer the top of the rpm range with a "normal" load on board.