This is a prop question.

[hudman]

Re: This is a prop question.

Every inch of increase in pitch will cost you approx 200 rpm. run your existing prop, and get rpm readings, and go from there.

 

[tommays]

Re: This is a prop question.

GM has 9 OEM marine builders on there sight

if you open the sights and read each builders specs Crusader is the only one that even brings up a forged crank

All of the builders tend to brag about there "better" ECM programing more than anything else

And god help us all they just devolped a set of manifolds with cats in them

Tommays

 

[MelLandry]

Re: This is a prop question.

Thanks for everything guys.

The motor is on its way up here. To answer a few questions:

"dont they sell Marine inboards? why would you want to take a crate motor and toss it in your boat unless your driving an airboat"

I have a second cousin that races 5.0 litre hydros and he called in a favor that got me this engine DIRT cheap.

"Just try your current prop, I have feeling it will be a bit small with the new motor, we need to know what prop you ran, and what speed/rpm did it do? "

That's what I plan on doing, and then going from there. I honestly don't know exactly what prop I was running, and I haven't seen the boat in a few weeks. I'll check when I get to hang out with it again. My biggest question was exactly what determines WOT.

"In answer to your question, most marine engines are propped close to their HP peak not their torque peak... That said, I don't know how you are going to determine at what RPM that occurs."

Hopefully when the engine gets here and I get all the specs on it, the mfg should know roughly what the peak HP range is.

And for the record: The only time this engine will ever be run at WOT is when I'm working on propping it.

Thanks for your help everyone. I'll keep you updated. Start brainstorming for this Winter's re-carpeting/upolstry project.

 

[Bondo]

Re: This is a prop question.

Mel,......

For the WOT that you want to be Looking For,...??... It's the Cam that determines the #....

I'd say it's Safe to shoot for 4600/4800rpms,.......
That's where a Truck/ Marine motor is Usually cammed up too......
If you get a "Build Sheet",.... It'll state the Grind of the cam,+ expected peaks.....

Besides,....... Your Drive will start to Really Complain when you start spinning things much over 5000rpms..................

My Thoughts on the Prop,..??.....

IF you were running a 19",..... You might get by with a 21" or 23".........

IF you were running a 21",...... You'll Probably have to go with a SSteel wheel to get the pitch you'll Need.......
Maybe Lots of Cup on a 23",....
Or just Regear the Drive........

Good Luck with it,+ Keep Us posted.............

 

[Texasmark]

Re: This is a prop question.

Mel,

Dusting this off one more time.

Now that "we" are going to move right along with this project, you might just run your old prop for awhile, just keeping your rpm's at/under your chosen 4400 or 4800.

It will surely be better on the break-in than a prop that is higher in pitch, hence higher in load on the new engine.

Then after 10 hours (I think cars were 500 miles....at 50 mph = 10 hrs for break-in) you might want to start thinking about another prop.

If you stay with the same mfgr and same style, then you should be able to follow the general rule of 200 rpm drop per inch of pitch increase.

And if you get a ported prop (holes in the side) your hole shot will be much better and the rest of the performance should be similar considering pitch change. I didn't mean to contradict myself on the previous paragraph, but I have seen some props that are ported only in the higher pitches; everything else the same.

Good luck.

Mark