posted 06-13-2010 12:45 PM ET (US)        

I measured speed with a Bushnell Onix 400 GPS. RPM and fuel flow were taken from the Mercury Smartcraft gauges.

The boat was 3/4 full of fuel. The boat was lightly loaded with me and my 2 girls. We have a rear seat in the boat, and the battery (70 pounds) is in the starboard rear of the boat. The boat has a notched transom.

The figures are rounded to the nearest tenth. We took multiple runs in different directions and averaged the results. We were on a lake, so there were no current considerations. Wind was light and variable. We had typical 6" to 1' chop on the lake, from boating traffic.

The data is not comprehensive, but still useful.

RPM		MPH		GPH		MPG
1000		5.2		0.7		7.4
2000		10.5		3.2		3.28
3000
4000		30.0		9.8		3.06
5000		40.0		13.3		3.00
5200		41.0		20.0		2.05

Try as I might, I could not get the RPM over 5200.

The gear ratio for this motor is 1.75, and WOT is 5000 - 5750 RPM.

The motor is mounted 1 hole up.

Some observations. The motor starts easily and runs very quietly at idle and low speeds.

The motor idled smoothly between 540 - 560 RPM. GPH at idle speed ranged between 0.2 - 0.3 GPH.

There was no smoke or smell. The sound made by the compressor when hitting higher speeds is quite distinctive, but not unpleasant. My perception is the motor is no louder at speed than my old 2 stroke Yamaha 70HP. Candidly, at higher speeds, the wind impeeded conversation far more then the sound of the motor. My girls were able to converse easily while sitting on the rear seat.

We seem to have overlooked 3000 RPM statistics. This is probably because the boat seemed to gravitate to the 3800 - 4000 RPM level. That seemed to be the sweet spot.

It looks like we can expect to get 3+ MPG at normal cruising speeds, which is great news. Even at WOT, where the engine really got thirsty, we still averaged 2.05 MPG.

Still, I would like to know whether another propeller would allow us to hit 5500 RPM? Andy Gere has reported good overall performance with a 4 blade Mercury Vensura, I think it is a 14" x 17.

I am looking for good overall performance, and am not concerned that I squeeze every last MPH out of the engine.

Any thoughts?

Thanks,

Dan

posted 06-13-2010 01:40 PM ET (US)            

Because you report a top speed of only 41 MPH @ 5200 RPM I am certain the prop has been repitched to a lower pitch, probably 19 or 20 inches.

Even if it was reduced to 19 inches of pitch (two inches is about all you can change a prop) you have propeller slip of over 23 percent, way too much for this situation.

This also demonstrates how repitching an existing prop is not always a smart move. It will not equal the performance of a prop that was made to the desired pitch in the first place.

It also means the prop is now close to worthless; there is little market for modified propellers when stock props are so abundant.

One could have easily sold a stock 21" Lightspeed and used the proceeds to buy a used 19" Lightspeed, if a pitch reduction was all that was desired. Instead, somebody paid a prop shop to modify the prop, the prop is not satisfactory and now it will be hard to sell for anything.

The high gear ratio of the OptiMax 225, 1.75:1, means you must use a relatively low pitch propeller; 17 inch is probably close to where you will end up.

That boat should easily be able to do 45 MPH with 225 HP. I honestly would expect it to be able to do much better than that, given that Jim Hebert's 22 foot Revenge Whaler Drive with its 225 horsepower Evinrude E-TEC is able to hit 43 MPH with a heavy cruising load and full canvas.

posted 06-14-2010 12:31 PM ET (US)            

My 1990 Revenge 22 W.T. with 2003 225 Mercury Optimax tops at 43 knots (49.45 mph) with a MiragePlus 19". Top RPM is only 5,200. Cruise at 29 knots at 3,750 RPM and a bit over 3.0 nautical mpg (3.5 mpg). I rarely cruise with my canvas up.

I also have a 17" Revolution4 4-blade prop which gets about 5,500 RPM (can't remember as I haven't used it for years) and a bit slower cruise at 3,750 (24-26 knots).

I think you can go faster with a different prop.

posted 06-14-2010 01:56 PM ET (US)            

Thank you for the information.

Those are some impressive numbers, both on speed and fuel economy.

Was there a particular reason you moved up to a 19" pitch propeller when you changed propellers, as opposed to getting a 17" Mirage Plus?

Like you, acceleration is not as critical to me, as I am more focused on overall good handling, performance and fuel economy.

I do not believe I am going to have an opportunity to try a couple of propellers before choosing one, so I will be relying on the feedback and data provided by others.

From a cost standpoint, I have found some good pricing for a new LH 17P Mirage Plus.

I expect to keep the existing propeller as a spare, as it has little resale value, and I know it will get me home.

Thanks,

posted 06-14-2010 02:07 PM ET (US)            

It was a financial decision.

At the time, the best price I could find for a MiragePlus 17" (with shipping to Alaska)was around $450. After talking to my Mercury Optimax dealer/service guy we agreed that the 17" would be the best and that a 19" would deliver fewer top RPMS, but still be within the 225 Optimax's operating range. With two kids getting ready for college, I chose a used (eBay) MiragePlus 19" for around $200. There were no MiragePlus 17s on eBay at the time.

I think I put the extra $250 towards college. I know I SPEND A LOT on two private college educations! I must have put it there.

posted 06-14-2010 02:09 PM ET (US)            

That is all nonsense. In fact, one of the great benefits of having a counter rotating single motor is that you can often pick up props for very little money.

I once bought a left hand MIRAGEplus on Ebay for $9.99 (who is going to buy a left hand prop by itself, right?)

posted 06-14-2010 02:34 PM ET (US)            

I can completely understand the reasons behind your decision. In a few years, I will have 3 in college at the same time.

Tom,

For the propellers which you recommended, it doesn't look as if I will have any problems finding a left hand version.
I am reaching out to a couple of marinas to see if they have any propellers which I can test. I suspect that will be the greater challenge.

Jimh,

Thanks for pointing out the environmental differences which might favorably impact JimP's performance numbers.

I think my own performance numbers show that I can expect to average 3+ MPG at typical cruising speeds, which is just fine with me. If a more appropriate propeller improves upon these numbers, that would be icing on the cake.

Clearly, the Optimax is a very fuel efficient motor.

posted 06-14-2010 10:52 PM ET (US)            

On ebay, there are 2 LH 17P Mirage Plus props for sale. One is a 14" diameter and the other is a 15 1/2" diameter.

Would one be better than the other? What, if any, are the performance differences between the 2 diameters?

Thanks,

posted 06-15-2010 12:29 AM ET (US)            

There is no such thing as a 14" diameter MIRAGEplus propeller of any pitch.

posted 06-15-2010 10:02 AM ET (US)            

Thanks for the additional information.

With some additional research, I was able to find the various sizes this propeller comes in.

posted 06-22-2010 09:50 PM ET (US)            

I doubt I will have an opportunity to record a wide range of data this weekend, but I will follow up with my observations.

I do not have the opportunity to test several propellers. I based my purchase on Tom Clark's recommendation, combined with the performance data provided by JimH, and others.

Thanks to everybody for your input.

posted 06-27-2010 09:49 PM ET (US)            

While I was not able to gather any statistics, I can say that my perception is that the new propeller performed better. Hole shot was improved, and I never felt the extreme slippage that I experienced with the original propeller, nor any cavitation.

I hope to gather statistics with the new propeller within the next couple of weeks and will post them to this thread.

posted 07-07-2010 08:59 AM ET (US)            

With 2 of us in the boat, half a tank of gas and 30 pounds of ice in the rear fishwell (alas, no keepers were caught this day), the boat cruised very comfortably at 3400 RPM, with a sustained speed of 30 MPH, as measured on my handheld Bushnell GPS.

This made for a very comfortable ride, in 1 to 2 foot seas with little wind on a 100 degree day. There was a considerable amount of boat traffic over the holiday weekend, and we did not try to open it up.

Dan

posted 07-07-2010 09:54 AM ET (US)            

We were cruising at 3700 to 3750 RPM with sustained speeds of 30 MPH.

I recorded us hitting 27 MPH at 3450 to 3500 RPM.

posted 07-07-2010 09:53 PM ET (US)            

Thanks. The boat is still pretty new to me, in terms of hours of use, but I am getting more confident in the motor and venturing further each time out.

The MiragePlus looks to be well suited to the boat and motor. I hope to determine what my top end speed is soon.

I continue to be impressed with the fuel efficiency of the Optimax. One of my concerns when I was looking to move up from my Montauk was the cost of fuel needed to operate a 22 foot hull.

I am burning less than a gallon per hour at trolling speeds. I have an 8 HP Yamaha kicker, 2 stroke, that I have not yet used this year. It has a purpose as an emergency, get me home, backup, but I certainly do not need it for fishing. I would rather keep my main motor running.

The motor also has plenty of power and is well suited for this hull. The boat is not stern heavy at all.

Based upon my limited experience, I would absolutely recommend the Optimax to anybody looking to repower a 22 foot classic hull.

It looks like you are seeing some great performance numbers from your setup. 49 MPH is not too shabby. How's your fuel burn at cruising speeds?

Dan

posted 09-04-2010 03:56 PM ET (US)            

However, we were out in the boat today in very windy conditions, 25 MPH to 30 MPH sustained winds, and the boat cruised nicely at 32 MPH at 4000 RPMs, in confused chop.

We had just filled the tank (77 gal), and we had the entire crew aboard, 5 of us in total.

Hole shot is excellent with this propeller and motor. You need to ensure everybody is sitting or holding on before hitting the throttle.

We have a rear bench seat, so everybody is in the rear of the boat, typically, when the boat is moving at speed. The boat will pop up onto plane quickly if we are accelerating to 3400 RPM or faster. But the boat does not plane at speeds below the low to mid 20's.

I think we could definitely benefit from trim tabs. Something to think about this winter. Of course, I am not certain that ranks above canvas, or new steering.