How long to reach top speed

garbubba said:
I'm at a loss here....

13.75x17 ss prop, 13 7/8x15 aluminum prop, 13.75x13 ss prop

You say all three of these props gave you the same RPM's at WOT? Comments about aluminum being different than SS notwithstanding the two stainless props are 4 inches of pitch different, they should give you way different RPM's at speed.


The tach sure seems suspect, if not something is surely wrong.
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Not always. 15 pitch doesn't equal x rpm and y speed for every prop. Some basic props can run say 5200 in a 17 pitch at 45 mph while a different style 13 pitch could turn the same 5200 at 42 or 43. Pitch is just one meadurement when it comes to props. Some props also have what we refer to as progressive pitch where the pitch varies across the blade, or you can have one with alot of cup in it, larger diameter, different hub, and so on.
 
Also, along with everything that TheFermanator just said, don't forget that different materials will also effect engine RPM's. You mentioned both Aluminum and Stainless Steel props.. Under load, while being spun against the resistance of the water, they both will flex, but at different rates. The aluminum more so than the SS. The amount of that flex also effects the final RPM's vs SOW of the boat.
 
And don't forget number of blades and prop slip. We went from 21 pitch vengence props on the neighbors boat to 18 pitch 4 blade michigan wheels(both stainless). The boat runs nearly the same top speeds, turns slightly less cruise rpm's at higher speeds, jumps on plane instead of just looking at the sky wishing it could get on plane(had have everybody move forward, trim both drives in, and run the tabs down all the way to plane out before), and runs 100 rpm's lower at wot. The searay 250 I did a few years back had similiar results. Went from a 17 pitch vengence to a 16 pitch mirage style, got it off the limiter, planed better, and ran alot faster.
 
Speed

My 1977 had a 1977 evin. 140 when I towed it home from Florida early Dec. which we checked out and they said it could run but the compression and condition were such we'd never get max performance out of it, it likely had been overheated as well and it wasn't worth putting money into rebuilds...technology. So, I looked around, found a 2008 Evinrude etec 175 with 300 hours and careful maint. history from a dealer and repowered. It had been running a 21' bass boat with stainless prop so they needed to re prop it for a deep v hull and started with an approx 14" or slightly less x21" pitch. Popped it in the river and ran it wot to 45 mph on gps. However the rpms were down so they re propped it with a 19" which it has now and the rpms should get to the max range of 5500 to 6,000. Not sure what the wot speed will be but it should cruise pretty well. If I had kept the 1977 140 I bet it would not have gotten more than 120 hp which is not enough for a big deep v hull in my view. The 175 pops it right out of the water they told me. I couldn't be there the day they did the prop work on the river but am eager to get it out when weather breaks now. It's ready and functional.
 
get to plane and speed with etec 175

I repowered with a 2008 etec 175 on my 1977 V20 and got to use it three hours Friday. The two stroke is a torque monster pushing a 14.5" x 19" pitch aluminum evinrude new prop.

Three hours of use, mostly cruising at around 2700 rpms and about 26 mph. 3000 rpms and 28 mph, 3200 and 30 mph easy cruising. 4,000 rpm and about 40 mph. I ran it into the wind briefly wot and it hit 48 mph with the nose trimmed down. I did not do it for long but it was doing 5,000 rpm and later learned when I started trimming during cruise if I got the nose up a bit it added 200 rpm and 2 mph so I think trimmed wot it will hit very close to 50 in flat water with just me in it and full tanks.

Up on plane with gradual acceleration...how about the torque monster does it at any rate you want. It throws it up on plane faster than any boat I've ever had...very few seconds if you want and no bow way up in the air stuff with the step lift..hit it medium, go more and you are up as fast as you can handle the throttle.

The engine is so quiet you can barely hear it. If you are idling along at 4 mph you can't really hear it at all.

In three hours of use constantly I consumed 7.6 gallons of gas from the starboard 20 gallon tank and never touched the port one. That's an average of 2.5 approx. gph which is way better than my former Mercury 3.7 l four cylinder 170 hp inboard on a Wellcraft 190 American i/o.

The new engines, this one had 300 hours on it and just serviced...are just phenomonal and lots lighter weight than the four strokes with way better torque as well as a two stroke. Smoke? Using the Evinrude high test synthetic oil it smokes not a bit and uses/injects from the oil tank based on computed/sensored need at something like 75 or 85 to 1 ratio depending on speed and rpms. Best engine I've ever seen.

The boat tracked easily at 48 mph and handles any wakes or waves I saw on the river like they were nothing. There's a reason they sold so many of these.

When I got back to the dock and got it on a windy day back on the trailer solo and pulled the drain plug...dry as a bone.

I'm pleased. The data is from my experience with a specific motor. Late March, 2017 at about 60 F outside.
 
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somebody posted in this thread that we should post some videos. i think we should do that! give readers a good idea of what to expect and too back up some of these claims.

lets have a virtual race! quickest to plane, quickest to top speed and fastest boat. im willing to wager a beer, lol
 
last week best i could do was 44.9mph SOG
best cruise (gps/smartcraft gph) 2.9mpg
and after switching props to a 17" mirage plus (1.5:1 gear case bravo)
i can get up on a plane in about 3-4seconds, about 50 feet
 
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