posted 07-13-2006 03:06 PM ET (US)        

The boat is powered by a F150 Yamaha four stroke. Before anyone even tries to tell me the boat is under-powered, they should try to run such a hull with the F150. I could pull three skiiers with it if I wanted to.

The hull PORPOISES. For those who have claimed that an OUTRAGE 20 doesn't porpoise, they either haven't been in such a boat or they don't know what porpoising is. I've owned many boats and have never had one act like this. When I trim the motor the whole way down, you can run in grease flat water without too much porpoising....Any amount of trim up and the hull starts to act like a dolphin. I've had the engine on every hole except the top most hole. I'm gonna try this one tonight. I am currently running a stainless 14.25 X 15P Powertech prop----this is an aggressive prop that is cupped and reported to have very little slip. I can easily achieve 5,900-RPM at WOT. My best fuel burn is less than 3MPG irrespective of the trim or speed of the boat. I've tried using a stingray hydrofoil, but this hasn't helped much if at all.

I"ve read on the yamaha performance pages (available on the Yamaha Marine homepage) that this engine is capable of pushing far heavier hulls over 40MPH and achieves fuel economy in excess of 3.5-4.0 statute miles per gallon.

My questions are as follows:

Does anybody have a 20 classic 'rage with a Yamaha 150 four stroke engine that could provide me with some of their performance info?

Do the classic whaler hulls not plain as well as other more classical V-bottom hulls (modified) that would result in lower fuel economy?

Is it unreasonable to expect over 3 nautical miles per gallon from a 20' outrage that currently has half a tank of gas in it, one passenger and no gear running on flat calm seas?

At WOT I am running about 35 knots and am burning almost 15 gallons per hour. At 4300 rpm I am running about 22 knots and am burning about 9 gallons per hour. At 3000 rpm I am just up on plane and am running at about 10-12 knots and I"m burning 4 gallons per hour.

I could have gotten this kind of economy with a much cheaper and more powerful 2-stroke engine.

posted 07-13-2006 07:00 PM ET (US)         

Using the old rule- worst case 2 stroke 150hp would burn 15gph.

posted 07-13-2006 08:45 PM ET (US)            

I.E. A boat with a heavy motor (such as the F150, or my twin 90 HP E-TECs) is easier to "porpoise" than a boat with a lightweight engine (like my 18 with the single 150 classic 2-stroke Merc).

Additionally, the height of the engine(s) has something to do with this phenomenon.

In my case, I intend to jack my motors up even further to see if I can make it more difficult to create this effect (but when I have two full coolers in the back, you can get it to do it pretty much no matter what!)

Re Fuel usage: No matter what technology you're running, to produce 150 HP, you're going to need about 15 GPH. So WOT economy numbers are generally the same between engine technologies.

The savings (and they are significant) come in the standard, mixed use that we all face. For instance, I don't do a lot of fishing, but I do spend about 45 minutes each way in a No-Wake Zone from the ramp to the big lake. That means 1.5 hours of every trip is spent at idle, generating about 12 MPG Economy (with only one engine running).

That translates to a full 1-2 MPG overall enconomy figure with TWIN engines than for the classic single engine, even though at cruise, I'm only seeing a marginal improvement.

Overall, with that F150, you're likely seeing much better economy figures when taken en totale.

Maybe not - but probably, and for most people.

Add the kind of usage that people like Elaelap here do - i.e. trolling for the denizens of the deep - you're likely to see SIGNIFICANT overall economy boosts.

I saw just such a boost last weekend, when I actually did settle down for some salmon fishing and spent a total of 10 hours in the boat, covering 70 miles and burning 10 gallons of fuel for a whopping 7 MPG economy figure.

I don't know about you, but compared to the 3.1 GPH I got with the old motor pretty much no matter what, and I'll take the 3.8 MPG cruise, 4.5 MPG overall and 7 MPG when trolling; because taken in aggregate, I'm seeing pretty good economy considering.

SO!

If you are indeed selling a restored 20' Outrage with new Yamaha motor, let us know - I'm sure there's someone here who would be glad to take it off your hands!

You just need to dial that puppy in a little and you'll be very happy. That should be a very good combination.

posted 07-13-2006 11:27 PM ET (US)            

2. Are your batteries under the console or in the splashwell? Moving some weight forward could help your problem.

posted 07-14-2006 11:42 AM ET (US)            

Yes, this boat did begin life as a Revenge W/T and it's been modified to more or less be considered an Outrage. I put a pilot house on it that weighs about 170 pounds----not too much...My engine is heavy---466 pounds, I think. And, I am running with a 45 gallon offshore bait tank mounted about 3 feet in front of the splashwell bulkhead....Lots of weight there for sure; plus 77 gallons of go juice, my fat kiester and whatever tackle I may be dragging out to the tuna grounds.....yes, the boat is heavy in the tail end.

I just finished reading a very comprehensive thread on this site about the porpoising phenomena (much credit to the authors is deserved here). This has given me some ideas as how to reduce my undesirable riding characteristics. I am going to raise the engine to the highest point possible and see what effect that has---it probably will be too high and I kinda expect the prop to loose bite and cavitate too much, but I have to satisfy my own curiosity. I have also ordered a set of Lenco 12X12 tabs. They'll be on the beastie next week if I get time to mount them.

posted 07-15-2006 02:27 AM ET (US)            

Several things have eliminated it --mostly--even with the bimini set. I added a second Opti battery in the front of the console. I added a second anchor and it's 15 pounds to the forward locker plus another length of chain and rode. Draining the baitwell and stowing more stuff forward also helps. Continued experience with the boat and how it likes to trim has helped also.

posted 07-17-2006 06:08 PM ET (US)            

I got to take the boat offshore the other day and was finally pleased to find the following handling characteristics out:

1. Porpoising is still present, but not as noticable when the seas are really sloppy. The boat is pretty rough riding when going into it, but I think this is just the way things will be with the hull design.

2. When going downswell or across swell, life is good. The boat handles well and is quite dry, though the pilothouse really makes it almot impossible for the skipper to get wet. In fact, I was able to sit down in the captain's chair for most of the 30 some odd mile ride back in to the dock and run at 20 knots (seas were pretty sloppy).

3. This rig is a trolling beast. I simply cannot believe how stable the hull is in the water when plowing either up hill, down hill or across swell at about 6-7.5 knots. This makes up for the porpoising tendencies when on plane.