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Over propped

S

skytow

Member
"I have a 28 Bert with carbed

"I have a 28 Bert with carbed Crusader 5.7 liter / 300 HP motors. Year is 2004 if that matters.

I plane easily at 1900 rpm with a nice cruise setting of 2200 to 2400 rpm. Full throttle brings me to 4100 rpm. I think the book says 4800 to 5200.

I'm not interested in going faster just making my motors last and decent economy. I have four blade 17X17 (IIRC!)

I might like to have a slower speed at idle for trolling purposes. I'm too fast even on one engine! I don't want to make that change until I have the boat hauled for the season.

Do you think I'm hurting anything in the mean time? I never run these hard except the one time to find the top end. I had 31 knots on the GPS at 4100 rpm!

Thanks,

JD"
 
"You might consider taking out

"You might consider taking out a couple inches of pitch. It will slow you down a little at idle, and allow the engines to get a little more HP, if you even need it at high throttle. In the meantime, as is will not hurt anything."
 
"Only addition is when it is t

"Only addition is when it is time to 'tune' the props, go find a shop that does PROPSCAN - its worth every penny."
 
"Could not agree more with PRO

"Could not agree more with PROPSCAN...My original props were probably balanced by drop kicking them across the factory floor. After the propscan adjustments, they were SMOOTH as silk and worked great...well worth the $$"
 
"I wouldn't touch a thing!

"I wouldn't touch a thing! Damn near perfect the way it is. With twin small blocks in a boat that size, a boat that planes so easily (and holds a plane to low rpms), you don't need to run high rpms at WOT. That just lowers gas mileage and wears the motors out sooner.

I know you'll get a bunch of guff fromthe "experts" out there saying otherwise, but they are quoting the party line without using their heads! (Conventional thinking.) My boat is set up to turn 3,900 rpms WOT and its perfectly happy.

Jeff

PS: At 2,500 rpms cruising speed (20 mph) you couldn't slip a pencil in the open butterflies in the carbs. I'll bet yours is the same way. (I marked the position in cruise mode then checked it later.)"
 
"Guys,

Thanks. You are con

"Guys,

Thanks. You are confirming my thoughts. She runs great!

I have to try and see how far the butterflies are opened at cruise. I'll bet not much as Fastjeff suggests.

The four blade props are absolutely smooth as silk now. The previous owner had just had them gone over by Accutech in NH and they use the Propscan system so I'm already spoiled. I simply don't know any better but they seem perfect to me.

Now to open a REAL can o'worms....

What was the tie in in to Kutztown I saw posted not that long ago??

JD"
 
I feel better after reading th

I feel better after reading these posts. I am also over proped.1984 31'Chris Craft Commander 315.250 Gal. fuel usually full. Twin original 454 ci.340hp Mercrusers 1.52 to 1 trans. WOT RPM 4400 .Repowered with 2007 Crusaders 5.7 EFI 320 hp. WOT 4000 @26Kn. Boat cruses 3000 @21Kn. "heavy" = lots of stuff.Using orig. props. 16X16 cup (I think).Spend most of the time @ 1500 unless I need to get someplace. Crusader recomends 5000 WOT.
 
Heck my new OverPropped WOT is

Heck my new OverPropped WOT is 3600...I just did a 60 mile run with the best fuel efficieny and cruise speed then when I first got the old gal.
 
"Al,

So what was your cruis

"Al,

So what was your cruise rpm and speed? What rpm and speed is needed to stay on plane? I believe the Crusader spec calls for about 4200-4400 @ WOT. If your WOT is only 3600 and suppose your cruise rpm is 3000, then you are operating at 83% of WOT, which is supposedly just about right, but any RPM higher means you may be straining the engines. My thinking is that is your WOT is 4400, then 80% would be 3500, and may provide the same speed but a little less strain on the engines. Does this make sense?

Erich"
 
..."What was the tie in in

..."What was the tie in in to Kutztown I saw posted not that long ago?? "

Just up the road from me.

Jef
 
".."What was the tie in in

".."What was the tie in in to Kutztown I saw posted not that long ago?? "

Just up the road from me.

Got it.... lived there for 17 years! Now down in FAR southern Chester County.... Closer to the bay!

I was wrong, the four blade props are 17X16 the old 3 blades were 17X17 but were behind old 230 HP Ford blocks......

:)

JD"
 
"Jeff; if those 4 blade props

"Jeff; if those 4 blade props use a 1 1/4 bore and if you end up selling, i might be interested!"
 
"if you want to go slower for

"if you want to go slower for trolling they make bags you throw over the side to act as Parachutes in the water, that way you can run at better than idle speed which is better for the engine. I've heard 5 gal buckets will also work, but i have doubts that the handles would hold under the strain."
 
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