posted 05-28-2009 01:09 PM ET (US)            

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Optis are destined to fail according to another post ;)

Actually I was going through local Craigslist and there were seven V6 Optimax engines for parts in the last two days between 2003 and 2006 years. There was one other engine for parts which was an older V4 OMC looper. Kinda scary if you think about it.

posted 05-29-2009 03:34 PM ET (US)         

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I could care less what engines this fellow buys, and don't even know what's available over there in Italy. But a Temptation 2500 can handle the weight of a pair of 3.0-liter Optimax motors.

The small 200 Evinrudes are being pushed to the limit for a 2.6 liter engine, while the 3.0 liter Optimax is at the bottom of its limit at 200 HP, this block being capable of about 275-HP. The Opti's will be loafing along, while the Evinrudes will be working a lot harder. If Evinrude is your brand of choice, get the bigger twin 200 H.O. motors for that boat. Will any of them do 55? Who knows, but surely not the small ones. I doubt if my 200 EFI's could push a Temptation 55 mph.

posted 05-29-2009 04:38 PM ET (US)            

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I had my previous set-up of Twin 3.1L Yamaha 225's push my Temptation to 57 with only me and about 20 gal of fuel aboard; no gear, no anchor, no cooler. I think 55 might be a bit optimistic for a pair of 2.6L 200's; certainly low 50's is do-able with a light load.

If price is your main concern, by all means, go with the cheapest. They will all push the boat fairly fast. I'd pick the brand that you can get the best dealer network of service from. If it's Evinrude, I'd slap some 225 H.O.'s on there. That will get you beyond 55 MPH cruising comfortable at 40 MPH.

posted 05-30-2009 08:22 AM ET (US)            

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If an Evinrude 200-HP E-TEC with 2.6-liter displacement is "being pushed to the limit," where does this leave the Mercury 2.5-liter 200-HP? Or the Mercury 1.7-liter 200-HP Verado that has to make 235-HP due to losses in its supercharger and other parasitic loads. By this reasoning, they must be pushed beyond the limit.

As for the weight on a Boston Whaler TEMPTATION 2500, with the Whaler Drive there is probably not as much concern. The Whaler Drive adds plenty of buoyancy when the boat is in the water. What would concern me is when the boat is not in the water. Large twin engines hanging on the Whaler Drive create a very high loading when not in the water.

posted 05-30-2009 11:07 AM ET (US)            

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I also enjoy the smell of 2 stroke oil in the morning. The deep throaty sound of pistons pumping out 100+ db of great sounding music quality internal combustion explosions is almost as good as a super model gently blowing in my ear.

If you want quiet, go out in the deep woods and hug some trees.

posted 05-30-2009 12:05 PM ET (US)            

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Regarding engine noise, my experience has been that in practical terms, there is little difference between traditional 2-strokes and DFI/4-strokes. Yes, I know there is a measurable difference in decibels, but I'm talking practical application. When you are at idle, normal conversation can be made standing or sitting next to both. I have not trouble with this while 2, v-6's are running. While underway, the wind becomes a far greater influence on sound transmission then the sound of my Yamaha 2-strokes. So 4-strokes/DFI's are a little quieter; what does that really get ya besides a burned out starter when you repeatedly try to start a motor that is already running.

Now the smoke-I could do without that, but it doesn't offset what I like about 2-strokes.

posted 05-31-2009 08:58 AM ET (US)            

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I have found when you equip boats (Whalers too) with higher and higher horsepower, the corresponding hull factor rises. Because of this, 180 should not be considered as a baseline hull factor for high horsepower Whalers. I have a computed hull factor of 217 with my current power (500 total HP) and 213 with my previous power (450 total HP)

The weight I generally use to calculate the hull factor for my Temptation 2500 is 6,300 lbs with just myself aboard. I would estimate just over 430 HP would be required to push a lightly loaded Temptation 2500 to 55 MPH assuming 210 hull factor.

posted 05-31-2009 10:40 AM ET (US)            

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TransAm--I agree with your theory of the HULL FACTOR change. As horsepower increases, the boat goes faster. As the boat goes faster, less of the hull is in the water. Therefore, the influence of the hull decreases with increasing boat speed. At some point with increasing boat speed there is almost no hull in the water, so it would be reasonable to think that the difference in resulting speed becomes less based on the hull's shape and more based on the weight, as well as the outboard motor gear case and its shape.

The speed predictions for Crouch's Calculator are based on moderate planing speeds for conventional hulls. As you push the speed higher, there could be an apparent change in the boat speed increase with horsepower-to-weight ratio.

I go back to an observation made many years ago by Clark Roberts in regard to the performance of a 15-foot classic Boston Whaler hull, which first expressed this idea. See:

http://continuouswave.com/whaler/reference/15/testimonials.html

posted 05-31-2009 01:47 PM ET (US)            

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Crouch says

LBS = 6300
HP = 400
HULL FACTOR = 210
MPH = 52.9

If a TEMPTATION 2500 has a real-world hull factor of 210, then hitting 55-MPH is marginal, but at least the boat would be in the 50-MPH range.

Working backwards from 55-MPH, we can find the power needed: 432-HP

posted 05-31-2009 03:10 PM ET (US)            

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[This article has been extensively edited--jimh]

I'm still thinking about the right repower rig. I tested my Temptation 2500 last year and here are the figures.

1988 Temptation 2500 powered by Twin 225-HP 1988 Johnson turning 3 x 14.25 x 21 OMC SS propellers; fuel between 70 to 85 gallons; two people; no gear; around 300 lbs.; no oil since I premix 50:1 with BRP XD 50 only. Wind was pushing boat on neutral at 5-MPH, no wakes while I was in Venice Lagoon. Temptation 2500 planes at little over 3,000-RPM and around 25-MPH. At WOT reached 5,400-RPM with very little trim and no trim tab, and 51-MPH easily.

Didn't pushed that hard, boat had anti-fouling paint, it was jet cleaned 30 days prior and left in water since that day. Also engine gear cases are dirty because I don't tilt motors out of water because of lack of space while mooring. I think I can gain 3-MPH more with boat cleaned, but not more. Boat seems to like cruising around 3,500-RPM with some 30-MPH. For me this is OK.

The problem now, before going to the water, mechanic told about an unfixable failure to engine power trim and also the need of an external gas pump, conclusion: around $1,500. These outboards are becoming too expensive for me. While have spotted on the www a 1992 3.0-liter Johnson 225 freshwater for $1,500, I'm wandering if stuck with the old OMCs or repower. I use the boat less than 80-hours per year, but maybe also because of cost of fuel and certainly a new rig will convince me to use the boat more.

About which choice: 2 x 175 Suziki four-cycle or 2 x 200 E-TEC small block. A top speed of 48- to 50-MPH is a good level for me. I'm also unable to tilt motors while mooring because lack of space. This for some six months per year. Maybe E-TEC motors are more corrosion free than Suzuki motors. I also have a Mastercraft with 2003 140-HP Suzuki and there is a lot of corrosion.

How much gas I will save each hour of boating with the new rig? Thanks for replying

posted 05-31-2009 05:25 PM ET (US)            

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I think the change in the Crouch factor only works if the hull has a combination of shapes at the stern such as a plaining pad. A 22/25 Whaler with Whaler Drive which has a flat section has that. A notched hull 22/25 Whaler doesn't. The more you can get a 22/25 Whaler to ride on the flat spot of the Whaler Drive instead of the V of the main hull, it stands to reason the higher the Crouch factor. Of course to get the Whaler to ride on the flat spot, you need lots of HP.

Regarding fuel consumption, under the ICOMIA duty cycle, a carbureted Johnson 225 would burn something close to 8 GPH. An E-TEC 225 is 4.4 GPH, the small block 200 is 3.7 GPH. Going from Johnson 225s to small block E-TECs should yield about a 4 GPH fuel consumption savings per motor if you ran your boat per the ICOMIA duty cycle. With two motors, that savings would be about 8 GPH. At $2.50 per gallon, the E-TEC 200s would be about $20 per hour less to run in fuel costs. 80 hours means about a $1,600 savings in fuel cost in the U.S. in that season.

posted 05-31-2009 06:07 PM ET (US)            

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I would agree 400 HP would not push a Temptation 2500 to 55 MPH. In fairness, the report of 51 MPH was with little trim, not pushed hard, and likely some marine growth on the outdrives. I would also be curious as to how the motors are positioned. I have found 25" motors operate best in hole #4 and could tolerate an even higher mounting position. My motors are mounted in #4 holes and I can take a sharp turn in either direction leaning the boat to what feels like 45 degrees and the high side propeller will not break loose. I can also trim the motors all the way up at high speed and not loose propeller grip.

I would agree with the "pad" theory as it related to the Whaler-Drive. In fact, I sought to advance that same theory here http://continuouswave.com/ubb/Forum4/HTML/006029.html .

Personally, I have not found the Whaler-Drive the performance-robbing appendage some have suggested it is in past discussions, and would argue that it has perhaps a positive impact on overall performance with higher horsepower.