posted 04-14-2008 08:42 PM ET (US)     

I had purchased a Turbo Lift airfoil from a place in Florida, as I had heard that planing is an issue with the 160D. I tested it with and without the foil.

Observations with the Turbo Lift foil:

posted 04-14-2008 08:54 PM ET (US)         

Observations with the Turbo Lift foil:

- planing began at about 14 mph and was fully on plane at around 19.6 mph.
- max. speed was 38.5 mph at 6300 rpm
- I had to continuously adjust the trim angle to maximize performance. It was way too sensitive. When properly trimmed at full throttle, you had to immediately trim it back down when slowing down or it would almost porpoise out of control.
- turning at high speed took a lot of effort (relatively speaking) even with hydraulic steering.
- If the trim was not perfect, the foil made all kinds of sounds.

- As you can guess, I was not happy with the Turbo lift setup (it is now for sale if anyone is interested)

Observations sans the Turbo Lift Foil:

- planing began at around 14.5 mph and was fully on plane at 20 mph
- planing rpm was around 3600 rpm
- top speed was 39.5 mph at 6400 rpm. I would have expected speeds more in the range of 42mph.
- boat was much less senstive to the trim angle. However, it did need to be fully trimmed in to get on plane in a reasonable time.

The lake was very smooth so I did not have a chance to test rough water. However, I have no doubt it will be perfect for this lake.

It seems that the Vengeance 15P is a little under propped for this boat/engine combination. I have a 17P Trophy Plus prop recommended by Marlin on this website that I want to test. Not sure what to expect.

Any and all comments welcome. I am looking forward to getting out again when the weather is a little warmer to do some further testing (I live in Chicago). In any case, I think I am going to really like this boat.

posted 04-14-2008 11:45 PM ET (US)            

I'm looking forward to you finding out the best setup for your Dauntless. Keep the comments and information coming.

I have a 2003 Dauntless 160 with a Mercury 115HP Fourstroke (a 2007 if they had model years).

I have been running a 15p Mercury aluminum prop -3 blade (I'm not sure of the model). My current tach only goes to 6,000 rpm so I can't give you exact RPMs. At WOT the engine is over 6,000 RPMs and the rev limiter hasn't kicked in, the speed is 41.5mph (GPS) going both directions on very calm water. This is without any foil. I have not noticed a particular difficulty in trimming the engine.

In the next few weeks I am installing a Smartcraft tach and a trim gauge, so I will be able to give better RPM & trim data.

I have been trying to keep it simple and vary only one thing at a time. I want to dial in the right prop on the right hole. Then I will decide if I need to get a foil.

Keep playing with the boat, I know you will happy. I will keep you informed as to how I'm doing.

Doug

posted 04-15-2008 09:18 AM ET (US)         

I only had a couple of days for some quick initial testing, but now have some baseline information to think about. I will definitely post further information as I get it, probably not until the end of May. What hole is your engine mounted in?

John,

I'll test the Trophy Plus and see what happens. I am a little concerned about the RPM at WOT, going from a 15P to a 17P. However, with a totally different prop, it is not comparable on paper. After that, your suggestion on the Laser II 16P (if it exists) may be another option.

In any case, I plan on just getting things dialed in and not become obsessive with testing.

I would like to have a trim indicator installed. Not sure how to do this. My understanding is that this engine (115 HP Four Stroke, made in 2007) does not have a trim indicator, even with SmartCraft.

posted 04-15-2008 09:32 AM ET (US)            

Congratulations on your new boat! I was a bit surprised to see that your top speed was so low, as I used to get 44-45 MPH with my 16" Vengeance and about 43 MPH with the 17" Trophy Plus. However, now I see that you're boating at just over 2000 feet instead of sea level, so that may well account for the difference.

I agree with your observations on trim -- the boat requires full trim-in to get on plane, and is very sensitive to trim settings from planing on up through WOT. Where my foil really paid off was in keeping the bow down at low planing speeds to improve the ride in choppy water. You might want to wait to get some experience with those conditions before you do away with the Turbo Lift.

Your hard steering might be corrected by adjusting the trim tab on the lower unit. Running with the engine trimmed somewhat in, my usual setting, it's much harder to turn to port. My trim tab is set with the trailing edge about 3 "clicks" to starboard to help with that. Of course, when running at fast cruise and trimmed further out, it becomes harder to turn to starboard. That's just the breaks, I guess. Interesting that you have hydraulic steering, I don't recall ever hearing about that as an option on the 160s.

As for your prop, generally I wouldn't expect that you'd improve your speed going from the 3-blade to the 4-blade Trophy Plus. It's possible, though, that if you're hitting 6400 with the 15" Vengeance, your engine might have a little more power left in it that could be harnessed by the Trophy. It's worth a try. In general I think you'll be happy with the shorter time-to-plane of the 4-blade.

Keep us posted on the results!

-Bob

posted 04-15-2008 10:31 AM ET (US)         

You bring up some very good points.

With regards to going from the 15P Vengeance to the 17P Trophy Plus, there may indeed be some more room for additional power. Actually, I was pushing 6400 rpm and felt I had a little more throttle, but was afraid of hitting the rev limiter, given that I only had a few hours on the new engine. Also, your observation of altitude is something I had not thought about. Lake Pend O'reille is actually around 2061 feet, as you correctly noted.

I had the dealer add the Baystar hydraulic steering after I tested the boat in Minnesota before shipping it to Idaho. It had the standard cable no-feedback steering which I did not like at all. Again, your point on adjusting the trim tab is significant. When I test drove the boat, it was VERY hard to turn to port. This would clearly indicate a trim tab adjustment may be needed. With the hydraulic steering, it is apparently compensating for this issue. This brings up a good point. With the standard steering, it seems rather simple to adjust the trim tab and see a difference. However, with hydraulic steering, it seems it would be difficult to make this adjustment, as the hydraulic system compensates so well. How does one do the trim tab adjustment with hydraulic steering?? In any case, having had the issue with hard steering to port with the manual system, I will definitely try the adjustment you noted and see what happens. By the way, I LOVE the hydraulic steering!

Finally, given that the trim angle is so important, I'm looking for how to monitor the trim angle with this engine.

Thanks again for your comments and suggestions.

Mike

posted 04-15-2008 11:18 AM ET (US)            

I made some assumptions about typical August weather and plugged in some numbers to compare your engine output with mine on the Potomac River.

Potomac River, MD
air temp: 87 deg F
altimeter: 29.92 in Hg
dew point: 65 deg F
altitude: 0 ft MSL
relative power: 99.2% (114 HP)

Lake Pend Oreille, ID
air temp: 80 deg F
altimeter: 29.92 in Hg
dew point: 55 deg F
altitude: 2060 ft MSL
relative power: 92.1% (106 HP)

If we stick those numbers into Jim's performance calculator at http://www.continuouswave.com/cgi-bin/crouchcalc.pl , assuming 2300 lb weights and a hull factor of 200, we get a speed prediction of 44.5 MPH for the Potomac, and 42.9 MPH for Lake Pend Oreille. Not that significant a difference.

posted 04-16-2008 09:07 AM ET (US)         

Interesting calculations. Looks like altitude reduces HP by about 4 percentage points for each 1000 feet increase in a linear way, all other things being equal. I'm really thinking that the 4 blade 17P Trophy Plus will put my WOT RPM's in a better range, with increased performance.

posted 06-13-2008 10:30 AM ET (US)         

The Trophy Plus made a big difference, both on planing speed and top speed vs. the Vengeance. I can now maintain planing speed of 17-18 mph, at around 3200 rpm with two people and a half tank of fuel. Top speed is now 42 mph.

The spec for rpm range on this engine is 5800-6400 rpm. At first I panicked when I could only reach 5200 rpm, but had not trimmed it out (duh!). Once trimmed out, rpm's reached 5900 rpm with 42 mph top speed. I think this is ok.

I had two full plugs in two of the prop vent holes and the other two had no vent plugs. I am going to plug all 4 holes as it seems to cavitate and vibrate a little coming off idle and going onto plane. It also it really hard to turn to port at mid range speed, so I think I will adjust the trim tab under the cavitation plate to see if this helps. I have hydraulic steering.

I do have one question. At WOT, there is a low pitch "droning" or long and slow "pulsing" from the engine or drive train, kind of like a sine wave if that makes sense. When I come off WOT, it goes away at all other speeds. Any comments here would be appreciated.

I really like the Trophy Plus and think it is a big improvement.

Mike

posted 06-13-2008 10:47 AM ET (US)            

Remember that trim-tab adjustments operate "backwards" (compared to the control surface they're connected to), so if you want to make it easier to turn to port, set the trailing edge of the trim tab to starboard. I'm using 3 clicks offset, perhaps 15 degrees. It's not enough when running on slow plane trimmed all the way in, but anything more would be too much at mid-range cruising speeds.

What you describe for the droning noise sounds like an interference beat frequency. That's common with twins, but with your setup I can't really imagine what it could be. Perhaps a mixing of engine/exhaust frequency and propeller blade frequency? Dunno.

Enjoy!