MPH question....

[Bubba]

Increasing diameter will drop your rpm's. I don't know how much effect it has on speed but it supposedly helps in load carrying ability while staying on plane.

Decreasing pitch will increase rpm.

There's the whole stainless vs aluminum thing too. You can turn a bigger ss prop than aluminum at the same rpm because of decreased flex and usually thinner blades.

Yeah...I'm just not sure if I wanna go with a ss prop tho. One because if something did happen to damage it...I would probably have to just buy a new prop.(i've heard they are more pron to just break if you hit something) And 2, I've heard that alot of times if you do hit something bad...that there is more of a chance in breaking something inside the lower unit rather than just bending the prop if you were to have an aluminum prop. So i'd rather just get a prop straightened out rather than buying a new prop or replacing/repairing my LU. That just kinda worries me cuz i've already bent my aluminum prop once. #-o

 

[Quackrstackr]

Hmm, I've never heard of anyone breaking a ss prop from striking something. I've heard of a lot of aluminum props breaking blades from striking something.

They can fix ss props the same as aluminum, it just costs a little more.

I guess it all depends on how often you strike objects and the severity of those strikes. A lot of duck hunters are switching to ss because they will take a whole lot more abuse than an aluminum and not even show so much as a nick. You would have to strike something fairly substantial to cause something other than just a spun hub and snap something in your l/u.

 

[G3_Guy]

That just kinda worries me cuz i've already bent my aluminum prop once. #-o

Were you running the same speed and turning the same RPMs before you bent your prop?

 

[Bubba]

That just kinda worries me cuz i've already bent my aluminum prop once. #-o

Were you running the same speed and turning the same RPMs before you bent your prop?

Yeah...That GPS speed was before my prop was bent.


I don't know, I still may look into a SS prop...just not sure. My biggest concern for hitting things is while i'm running at night...thats how I bent my last prop...and its dreadfull just idling all the way back to the ramp. :shock:

I'm gonna try to get some more accurate calculations and go from there.

 

[Bubba]

Well guys, A slight update here.

I opted out of doing a jackplate at this time, and figured I would just trying raising my motor up just abit. So me and Wes(whj812) tackled it this past saturday. We moved it up 1 hole, which I figure raised it up maybe an inch or so.

The main problem i've been having recently is that with a load(2 guys, tackle, etc) when I try to get it to WOT and get the motor to that "sweet spot" where it starts to smooth out, it starts porpoising. When its just me, it seems to do good. And I think moving the motor up helped that porpoising just abit(was doing it worse I think), but its still doing it.

I think I am gonna have to look into a new prop eventually...what do you guys think?

 

[Quackrstackr]

It sounds like a definite prop issue to me.

Did you pick up any rpm's when you raised the motor?

My boat wants to porpoise on me when I run it at half throttle unless I have it trimmed nearly flat. The prop geometry just can't hold the boat at a higher attitude given the rpm.

 

[Bubba]

It sounds like a definite prop issue to me.

Did you pick up any rpm's when you raised the motor?

My boat wants to porpoise on me when I run it at half throttle unless I have it trimmed nearly flat. The prop geometry just can't hold the boat at a higher attitude given the rpm.

I may have picked up some rpm's if I were to trim it up the same amount as I was, but I don't think it was hardly trimmed up as much to get the same rpm's as before. So the rpm's were running about the same I think, just trimmed abit less before it started porpoising.

I am thinking the same way as you. From what I understand, if the prop doesn't have enough "grab", it just doesn't have the "oomph" to keep it up on plane, so it tries to fall off plane, thus the porpoising.

I believe the next thing i'm gonna look into is a SS prop...probably something with similar specs as to what I have now. Eventually anyway.

 

[Quackrstackr]

Is this porpoise at WOT?

If so, did you try to trim it above where you normally would and get the rpm's up to see if it goes away?

You should be able to hit 5.5k to 6k easily before getting into the limiter.

Is it possible that you just are not airing it out enough to keep it from porpoising? I know when my boat is fully up on the pad and running all out, it doesn't feel like there is any boat in the water. That is a strange sensation for people that are not used to a pad hull.

Conversely, you may have too much pitch for the weight given that particular prop geometry. With a very heavy load during duck season, mine wants to porpoise if I trim it very much. Being overpitched can adversely affect your top end just like not having enough. You definitely do not want to lug a 2 cycle engine.

 

[Bubba]

Is this porpoise at WOT?

If so, did you try to trim it above where you normally would and get the rpm's up to see if it goes away?

You should be able to hit 5.5k to 6k easily before getting into the limiter.

Is it possible that you just are not airing it out enough to keep it from porpoising? I know when my boat is fully up on the pad and running all out, it doesn't feel like there is any boat in the water. That is a strange sensation for people that are not used to a pad hull.

Conversely, you may have too much pitch for the weight given that particular prop geometry. With a very heavy load during duck season, mine wants to porpoise if I trim it very much. Being overpitched can adversely affect your top end just like not having enough. You definitely do not want to lug a 2 cycle engine.

Yeah, Its at WOT, but i'm afraid the porpoising only get worse the more I trim the motor up.

As of this past sunday, just before it starts porpoising, it was showing about 5200rpm...give or take a few. I know the max recommended rpm range for my motor is 5500.

I am gonna try it out abit more on DH if the weather clears out for abit. Try it with just me in the boat, see what kind of rpm's i'm getting, fiddle with the trim abit more as well.

 

[masterofillusion]

How fast is your boat now? I had a G3 w/ 60 yamaha stock would do 42mph. I used to take my prop in to a guy to repair it, and asked him about stainless. He said there was not enough difference to make it worth while. Then he picked up a bent shaft and said "That's what a stainless prop will do". Personally I would rather break 100 aluminum props than risk 1 motor.