Prop pitch and size change

[Newyota]

correction - max RPM under normal load.

as said above: Smaller motors react more to pitch changes than larger motors.

buy yourself a tiny tach and set it up and find out what RPM you’re actually getting before doing any changes.

But: prop shops normally will go +/- 2 pitch on a prop. So if you are getting near 6k on a 5-6k max RPM and 5.5 is the sweet spot, go ahead and have it refurbed +2 shouldn’t hurt too much. But you need accurate numbers first.

Thanks for thre info.As I new my rpm reading due yo installing tach last year.

 

[hardwater fisherman]

Now, can someone smarter than me tell me why I went to the river today and decided to change my tilt pin from top hole to middle hole and I had a lot less wind today and going up river full throttle I was at max 5800rpm and last weekend hitting almost 6000rpm with tilt pin on upper hole and a descent amount of wind considering I am in a 14 foot boat.River did drop a foot since then.Curent may have been less.

Maybe the top hole is too high... Have you tried some of the other holes to see what happens to RPMS and speed?

 

[Newyota]

Maybe the top hole is too high... Have you tried some of the other holes to see what happens to RPMS and speed?

Read my previous post where I stated that I moved it.Thanks

 

[hardwater fisherman]

The only thing I saw is that you asked why you had 6000 rpms in the top hole and 5800 in the middle hole... And I suggested that maybe the top hole was too high... If the prop might be close to breaking the surface I would think the motor would rev higher.. I know I get different rpms and speed by moving the tilt pin..

 

[Newyota]

The only thing I saw is that you asked why you had 6000 rpms in the top hole and 5800 in the middle hole... And I suggested that maybe the top hole was too high... If the prop might be close to breaking the surface I would think the motor would rev higher.. I know I get different rpms and speed by moving the tilt pin..

Thanks that is the kind of feedback I was looking for.I changed the pin to try that before you posted.Your the first person that stated that could be the cause.I understand where your coming from..An engine should rev the same I thought at full throttle regardless in the water except maybe out of the water completely.If your right then overevving must be a common problem under certain conditions.I don't think it is good to be 500rpms over the max for a period of time .My little boat is fast though at 6000rpm!?It was very windy and a good chop on the water the day it was 6000rpm also.I have had prop ventilation issue in the past even at slow speed on a very choppy day.Thought my lower popped out of gear ,but it was the rolling waves under the boat.Tilt pins sometime need adjusted due to weight change or water conditions?Further testing to come and when I get my repitched prop I will see what goes on then.

 

[jakedaawg]

By having the tilt pin higher you may have had more of the boat out of the water. The motor wouldn't have to work as hard and higher max rpm would be attained.

 

[Newyota]

By having the tilt pin higher you may have had more of the boat out of the water. The motor wouldn't have to work as hard and higher max rpm would be attained.

Thanks..Since I am in a rocky river I like to run it a lot on the top hole to try to keep it away from them.At high speed it apparently is not a good idea when I am in a clear channel and over revving can occur.Without a tach I really would have not known it was overrevving.Just thought it was fast due to a smaller boat and a bigger motor since I went from a 9.9hp to this.

 

[jakedaawg]

Yeah, I doubt pin position will keep you from hitting anything, it just doesn't make a whole lot of difference. A few inches maybe, less when on plane. I'd rather hit the skeg and prop than the nose of the bullet...

 

[Newyota]

Yeah, I doubt pin position will keep you from hitting anything, it just doesn't make a whole lot of difference. A few inches maybe, less when on plane. I'd rather hit the skeg and prop than the nose of the bullet...

Agree with that..Do you think the average boater without a tach is overrevving motors and not knowing it?I just did not want to continue running that far over the max.Not sure how far over the max you can get away with without causing long term damage.My motor was already running way lean I discovered last year(only owned it a few seasons) due to fuel pump gasket not sealing properly.No telling how long it had done that,supposedly in storage many years till I got it.May already done damage due to that.See what happens with repitch rd prop at the lower pin setting soon.thanks again

 

[Sea Rider]

If plan repairing the 11 pitch prop, once repaired go for a wot run as will be loaded on flat calm water cond with a tach that's working spot on, once knowing accurate achieved max wot rpm will know if need a + size pitch and by how much, you can always play repitching half pitch (0.5) sizes in the +,- range besides traditional one full pitch resize..

Happy Boating

 

[Sea Rider]

Now, can someone smarter than me tell me why I went to the river today and decided to change my tilt pin from top hole to middle hole and I had a lot less wind today and going up river full throttle I was at max 5800rpm and last weekend hitting almost 6000rpm with tilt pin on upper hole and a descent amount of wind considering I am in a 14 foot boat.River did drop a foot since then.Curent may have been less.

Seems that you've been experiencing bad boating, this is the correct procedure you should be boating with, try it..

Distribute deck weight evenly...


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90 deg is the correct boating trim for top prop thrust recreational boating, doesn't matter if the rpm went up/down while playing with other trim settings aside from fully vertical, you can make the motor to rev where you want it to rev with a correct prop maximization...


Happy Boating