More Speed - for fun.

[highpowerdad]

Looking to get more top end out of a runabout... because...

Boat is a 2005 Fourwinns, 190H, with VP 5.0 GXI 270. 1.51gear ratio, running on average 3500 lb. It is an aft end heavy boat...

Props that I have and use...
1. Powertech MQS4 16 for pulling/watersports and it is great, boat is on a plane in ~3 sec, no shortage of power, will pull a tube with 4 teens on it and 4 more in the boat, will overrev long before topping out.
2. Powertech MQS4 -18, great for cruising, good hole shot, good handling at any speed, tops out a 53 MPH right at 5,000-5,100 with a light load, probably 49ish with a heavy load - never really run it WOT with 7-8 people in the boat.
So, (again, not trying to solve a problem, just go faster with the setup I have ...for fun). What would give me just "top speed" but with "safe handling". I say that because the original 3 blade SS VP that was on the boat would hit 53ish, but it was truly dangerous in anything by perfectly still water - the MQS4s took care of that and I sold the VP prop..., so it is "top speed, but some stability. I was thinking the same Powertech MQS, but in the 3 blade, and up the pitch to a 20, so MQS3 20P. What other options are there, if I stay with Powertech, the thrust washer and all is the same, so one setup, but ...what gives top speed on an aft heavy IO... what say you?

Thanks
Scott R.
Orlando

 

[jimmbo]

53 isn't all that fast. Were you Way Over trimmed?
If you are only dropping 2mph with 7 additional People, You are doing well

If you are trying for more Speed, fewer Prop Blades will help. Also leave the Wife, Kids and the Mother-in-Law, especially the Mother-in-Law ashore. Girl Friends and Mistresses can remain aboard

 

[airshot]

Can't have it all.....speed comes with sacrifices....less weight.....high rpm if your motor has the power to spin a higher pitch prop without lugging. Trim is for fine tuning tool for maximum performance but won't gain any serious amount of speed. You can always dump money in your motor to gain more hp....speed does not come cheap...

 

[jimmbo]

You can always dump money in your motor to gain more hp....speed does not come cheap...

Raising HP by hopping up the engine, may result in a bit more Top End, but that usually means poorer Acceleration.
More Displacement is the best way to make a boat go faster, if not, then a Blower would help, but then the Rotating Assembly takes a beating

 

[cyclops222]

Faster top fast speed is never safer. Faster speed means more invasive surgery and a body cast.

 

[jimmbo]

My boat, in the Avatar comes close to 70mph. I certainly wouldn't try deviating from a Straight Path though

 

[jlh3rd]

Raising HP by hopping up the engine, may result in a bit more Top End, but that usually means poorer Acceleration.
More Displacement is the best way to make a boat go faster, if not, then a Blower would help, but then the Rotating Assembly takes a beating

yep.
I went from a 60hp to a 115 hp motor on my pontoon. I gained only a 6 mph increase in speed....double fuel usage...
speed costs money...

 

[Texasmark]

Can't have it all.....speed comes with sacrifices....less weight.....high rpm if your motor has the power to spin a higher pitch prop without lugging. Trim is for fine tuning tool for maximum performance but won't gain any serious amount of speed. You can always dump money in your motor to gain more hp....speed does not come cheap...

"but won't gain any serious amount of speed." SAY WHAT???????

 

[highpowerdad]

Sorry, I think I must have asked the question wrong, what I am looking for anyone with experience with props that are more for top speed than the pulling and cruising props that I currently are using. I am assuming that a 3 blade prop will get me 1 or 2 mph, but if someone has actually run certain props and knows that prop A was really good for speed with aft end heavy runabout and prop B really didn't do much, and was a bear to control at speed, then that is the information I am looking for. I know if I really wanted to go FASTER, I would drop a 6.2 stroker in, or get a go-fast type boat ... that is not what I am asking.

 

[jlh3rd]

I guess what some of us are trying to say is that no matter what type of boat, different props can be used for fine tuning, as you have seen. But no prop is magical.
FWIW. I went through 3 props that all gave me the same performance #'s . A merc.4-14x14, merc 3-16x13, and a Solas 3-15.5x13. All speed/gph/rpm #'s were identical, and gave speeds around 25 mph@WOT 5800.
I ended up running a merc. 3-16x12 to get higher rpms for pulling teens on tubes but I lost about 3mph at 5800 rpm.

 

[jimmbo]

Unless you are running quite aways outside the WOT Range, adding/subtracting Pitch, within the same Prop Line, usually results in very little difference in Top Speed, but noticeable differences in Hole Shot. Changing to a Higher Performance Prop Model, can allow changes in Setup, which can increase Top Speed, and better Grip on the Water, with Hole Shot all over the Map.

The Mercury Enertia is a Prop that can add 1 or 2 Mph, and still improve Acceleration. I have been running one for 20yrs.

 

[cyclops222]

The most important factor of maximum speed is

 

[cyclops222]

Prop efficiency.

 

[airshot]

Bottom line is.....you will only go as fast as your motor will push your boat. You need to be within the wot rpm range or your putting excess wear on the motor. Once you get into that range, you have used the motor HP effieciently. Changing props will only change your top speed a few mph one way or the other....just the way it is !!