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Heavy boat do you change prop

E

Ewan

Guest
"Hi all just looking for a gen

"Hi all just looking for a general answer to this,

When you run a heavy boat over your normal running load should you have a prop more suited to taking more load or should you just stick it out with the current one?, if you should have anouther prop do you go up or down in pitch from your normal one?

example

normal boat load and 3 adults 25mph 3700 rpm, normal boat load but with 6 adults and great dane 20-22mph 3700 rpm, would this loss in speed be enugh to require a spare prop? since its a 2 min job to change prop

looknig foward to any answers this my bring up

hope it all makes sence

Ewan"
 
From what i know it all depend

From what i know it all depends on the boat and what your usual running RPM's are..if you find yourself running too high with more passengers i would install a prop with a higher pitch which would lower your RPM's...if it is opposite install a lower pitch...but also from what i understand if your running at normal RPM's and speed I wouldn't go too crazy in switching the prop
 
I'm no expert but my under

I'm no expert but my understanding is if your rpm is in its power range with both load arrangements and all your losing is speed with heavier load more pitch will add speed if you have the hp to keep your rpm's up in the power range. If not enough hp you may loose rpm and subsaquently speed by adding more pitch not to menting luging the engine.

Is the 3-5 mph speed loss still keeping you on plane? And is 3700rpm wide open throttle?
 
"Ewan

Unless you are not pa

"Ewan

Unless you are not particularly happy with the boats performance the way it is setup now, when carrying your normal cargo, you only have a few different options.

1) You can rather turf out 2 of the additional adults or 1 adult and the Great Dane and leave the prop on it that you are running now and you can probably split the difference and pick up 1 to 1.5 mph. (big deal)

OR

2) You can keep a few different props in the boat and change them every time you add or subtract an additional person or 2.

OR

3) you can leave it the way it is and just accept that the boat will not perform at its peak with 6 Adults and a Great Dane on board.

I think I would select option 3 if I was you.

Cheers
Peter C"
 
"Option 3 seems like it or ill

"Option 3 seems like it or ill just kick everyone one else off and stick to me and the dog,
with the heavy boat the wot rpms drop to 4100rpm which is below mercruisers running limt which is a proplem as there will be times when 4-5 adults will be aboard"
 
"Ewan
The dog probably wont g

"Ewan
The dog probably wont give you as much grief as the other passengers.
The running WOT min RPM scale is a guide for long term use, if your engine was going to be restricted to that long term it would be a problem but every now and then when you choose to pack in the extra campers it is no big issue.

Cheers
Peter C"
 
most motors have in their owne

most motors have in their owners manual or on the serial number tag the RPM range that the engine should run at. Being near the max operationing range is the optimum point. If you are below that range you would decrease the pitch and if you are above it you increase it. RPM is much more in=mportant than speed.
 
"John

Welcome aboard and go

"John

Welcome aboard and good point, middle to high on the RPM scale at WOT is the best place to be long term and where the engine is its most efficent.

Cheers
Peter C"
 
"Normal WOT with my current pr

"Normal WOT with my current prop is 4400rpm with a 17inch pitch 4 blade, to a 15inch pitch 4 blade reason for 4 blade is that I im going to for just cruising middle range speed and planing, any pros and cons to this?"
 
Five hot chicks don't weig

Five hot chicks don't weigh very much! That Dane is a chick magnet especially during spring break. Just have your affairs in order before you go to spring break.
 
"Damm Guy
You do have all the

"Damm Guy
You do have all the good tips, are you speeking from experiance.
wink.gif
"
 
"That sounds like a good idea

"That sounds like a good idea for use of the dog, but lacking a couple of things in Scotland, spring break and the chicks at the marina boating here isnt like there.

Before I go changing the prop I think that i'll install a Lowrance fuel flow system and get some figures from that as ive got one sitting waiting on getting fitted for 2 weeks now any views on that??

I thought it was about time I registered on here after getting this amount of advice so thanks all.

Ewan"
 
"Ewan

The Lowrance fuel flo

"Ewan

The Lowrance fuel flow monitering systems are great, I would fit one to mine but I think if I could actually tell how much fuel I was consuming at our prices it would scare the hell out of me.

Thats a real bummer, no chicks at the Marina, you need to move to Australia Mate !!.

Cheers
Peter C"
 
Nahh! I just watch it on the

Nahh! I just watch it on the tube and dream of how many chicks I could get on the boat. Young at heart but just an old fart!
 
"Guy

The sticker from our w

"Guy

The sticker from our waterways authority says I can carry 12 overall, that actually means just me, my long suffering wife and an occasional daughter and boyfriend.

Like you, the bevy of beauties is just a dream.

I can relate to the old fart thing.

Gee we have come a long way from a prop question,
oh well doesnt matter.

Cheers
Peter C"
 
"but we arent far form the pro

"but we arent far form the prop question as for when we all have a boat that runs great and smoothly it makes us all young with a drooling grin.

As to the prop thing ive ordered a 15inch pith 3blade aswell as getting my 4blade re pitched to 16inch so will post results to how it runs with each of these new combinations, the plate on top of the flame arrester says running rpm is 4400-4800 so im hoping to be within this range

thanks all for the advice"
 
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