Cruise speed...
 

I'm expecting low 90's out of my new boat and curious as to where that puts me for cruise?

My last boat did 64 at 45-4600 and I cruised at 49-50 at 3600. I think it was over propped a bit for top end but mainly cruised so enjoyed the faster speed at 35-3600.

Thanks

There's a ton of variables left out to even begin to guess

Without Vessel View or something similar to give you hard data, you will have to judge it by the feedback the boat gives you.

I would think some where between 60 and 70 mph @ 4000 rpm cruise

I figured that. Motor is starting to come together so I am trying to keep my sanity by thinking about something else other then the ups man dropping boxes off at my house.

I think I'm starting to see a light at the end of the tunnel.

Can't blame you for dreams of actually boating instead of writing checks!

Isn't that the truth. I bought this boat last fall went straight how and pulled the motor the next day. That's when the dreaming and watching YouTube started. Trying to see pictures and videos of what my new boat looks like in the water. Lol

top speed is a hard number that can't be argued. it either goes that fast or it doesn't. cruise speed is totally an opinion. low 90's top speed, one guy will say 35 cruise. another guy will say it cruises at 88...my idea of cruise speed is the number above which she digs her fingernails in my arm...

I usually cruise at 35-3600 rpms at least in my last boat.

When the hull lets lose an the motors reaches best econo. 38 Cig twin step. 4200 72 MPH . Worked for us on long runs.

70 percent of full load rpm. 5400 x .70= 3780. We use 3500 rpm

Don't remember what power you were upgrading to but I'd be shooting for low 60's in the 32-3400 range for an economical cruise.

I dont think the motor will be in the rite tourq range at that low rpm .

find out where max tourq is and that will be the ideal rpm range to cruise at . most big block's seem to be around the 4000 mark give or take a few hundred rpm

The stock motor was a 502 mag efi (415 hp). The new motor is a 509 with a b&m 250, cam, mild ported heads (088) and roller rockers. I've read similar builds having 650-675hp, but that's what I've read so time will tell.

What Prop pitch (1) and Drive Ratio (2) are you going to use?

Then, Cruise RPM x (1) / (2) / 1056 ( I use 1056 cause it usually gets me very close without having to calculate slip )

that formula will get you real close to your real world #'s

That's a cool formula. I had to use 1150 vs 1056 to get my numbers right. I cruise at 3500 at 65mph GPS running a 32P Bravo 1 (stock).

Install 1:36 gears and toss the 1:50's. You will cruise a lot faster turning a much lower RPM then a 1:50 with a higher top speed. The 1:36 gears are also stronger then 1:50's:daz:





































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If he switches to 1.36's then he has to decrease prop pitch by 3" or so to get the correct WOT rpm range.
1.36's spinning a 26" prop and 1.50's spinning 29" prop will still yield the same cruise and wot speeds within a couple mph.
1.36 gears might be just a tad stronger, but nothing huge.

do you know for a fact that the 1.36 gears are stronger than the 1.5's? i thought it was the other way around because i thought the 1.5 gears were slightly bigger. not sure tho
help mr gadgets????

Yes, the 1:36's are slightly larger. Correct, he will have to decrease pitch to get his his desired RPM. 1:36's are like starting off in second gear in a car, once you put it in gear you are moving at just idle! So right out of the gate you already are are up on a 1:50 operator. top end is also good for 3 to 4mph