Do I have right prop?

[Vipercwf]

1989 four winns 235 sundowner OMC cobra 5.7l 260hp. Just put a 19pitch prop on took it out w me and one other person WOT 4400 rpm. Put on 4 more people (500plus lbs) WOT 3800-3900. Is this okay? Opinions or suggestions? Thanks in advance

 

[180shabah]

Re: Do I have right prop?

I am guessing that your WOT spec is 4200-4600(verify this) so lightly loaded the 19" is fine, but with the extra people you are lugging the engine. A 17" prop would work better for this situation.

 

[Silvertip]

Re: Do I have right prop?

Start with ensuring the engine is properly tuned and making full power. Far too often performance begins to drop and people rush to change props when a simple tune up is all that's needed.

 

[Vipercwf]

Re: Do I have right prop?

Thanks for the advice. I actually previously had a 17pitch on it. The guy before me did alot of water skiing so thats why he had a 17 on it. The weird thing is with the same amount of people (6) it was running above 5k rpm WOT which doesn't seem to quite add up with the pitch to rpm difference.

-The 19pitch actually Felt awesome, it dug really good and planned really well - it just felt smoother no vibration or anything like that (with all 6 people on board). Since it is holding in the 4500 range with 2 people but about 4ish with more people (6) at WOT which one do I base it on? Since it seemed to ride so well esp out of the hole w 6 people is it okay to leave the 19 on or would I really be hurting it if with 6 people WOT its only gettin to like 4k rpm.

 

[180shabah]

Re: Do I have right prop?

Nasty things happen when you lug an engine(that is why there is a minimum rpm on the wot spec).. Increased combustion pressure, excessive heat, tuliped valves, head gaskets if you go long enough.......

If you are going to be running under different load conditions you might consider having two different props or run the low pitch prop (for the heavy load) all the time and just be very careful with the throttle to avoid an over-rev.

 

[Vipercwf]

Re: Do I have right prop?

Thanks for the advice, its greatly appreciated.