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1988 Wellcraft Nova 3 performance notes/questions:

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Old 07-07-2007, 01:12 AM
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Question 1988 Wellcraft Nova 3 performance notes/questions:

1988 Wellcraft Nova 3 performance notes/questions:

When I first bought this twin engine, stepped hull sport boat, it had bottom paint, stock engines (Merc 350 mags), both props rotating clockwise (21P-Alpha 1), conventional thru-prop exhaust and did 55mph on GPS. Iíve always believed this boat was capable of more performance and have taken significant steps in search of greater speed, but have not yet gained the desired gains in performance.

What I have done: replaced both engines with remanufactured Merc 350 mags, installed new IMCO Powerflow exhaust manifolds, stainless risers and thru hull exhaust, new counter rotating lower unit so props now counter rotate OUTWARD, bottom paint stripped off with chemical peel method leaving a barrier coat (primer) that is no smoother than the bottom paint. And now the boat runs great and sounds great but Iíve only gotten 50-52mph on GPS and the engines only rev around 4200rpm (normal operating range should be 4600-4900).

My speculations: stepped hull Fountains rotate their props inward for max performance because it lifts the rear of the boat and ostensibly reduces drag, resulting in higher top speed. Perhaps when both props were going the same direction, some additional lift was present allowing for slightly less drag. The bottom paint I had stripped off revealed a barrier coat probably didnít reduce the drag. According to a local propeller shop, the props have perhaps too much ďcuppingĒ on the following edge. The performance exhaust I installed has probably given the engines additional power potential but have not delivered the desired performance due to factors such as the rotation of the props outward, the non finished hull and the props having perhaps too much ďcuppingĒ on the following edge of the props.

Action items: Iím having the props re worked to take out some of the cupping to hopefully gain an additional 200 RPM or so. Iím going to sand the barrier coated hull down to gain considerable hull smoothness. Iím going to switch the prop rotation so they rotate inward to lift the back of the boat.

Anyone care to comment on whether these actions are likely to give me the 60mph or so I hope to achieve? If all else fails I may install different engine cams to boost the horsepower of the engines.
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Old 07-07-2007, 02:19 PM
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just a couple of thoughts; its entirely possible that the reman motors are not yet broken in and/or making less hp than the old mills. probably not the case but make sure the drive ratio is the same as the old units. did you make your previous speed runs under the same climatic conditions ( elevation, humidity, temp. etc) ? why not try different props before you have the cup reduced? good luck. - jeff
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Old 07-07-2007, 09:24 PM
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I do not think that this is a stepped hull but rather a straight deep vee. You will need lots of HP to get speed and the correct set up. You need to prop for more RPM. Maybe less pitch but watch your slip %.
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Old 07-09-2007, 02:18 PM
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Thanks for the input. Props are already modified, so we'll se what happens there. As for the difference in the conditions when I ran 55mph vs. other times at 50mph, I'm not sure exactly. The hull does in fact have a step in it and I'm happy to send out a photo if you're interested. I know this is not the case with most Novas.
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Old 07-09-2007, 03:08 PM
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Stott,

I had an 87 27 Nova III in the early 90's we had blast with!! Decent on fuel, ran low to mid 60's on the speedo w/55 gals. fuel(1/2 tank) and it too had a step. We were running 13 3/4" - 21's about 5k rpm's. We were spinning two right hand Alpha's. Not a rocketship but I spent a lot of time on the water when the buddies were working on their faster boats. I sold the boat for $500 more than I paid for it three years earlier. Wish I had that luck with all my toys!

Have Fun!!

Katz
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Old 07-09-2007, 03:11 PM
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I know a guy with a nova 3... it does indeed have an early stepped hull. nice boat.

he's getting a bit more speed than you, he didn't do motors but did do exhaust and props, tuned everything up, etc. He's only running 55-60, though, not much faster than you're going.

Once the motors loosen up a bit you will gain some speed. A fresh motor will often be a little down on power.
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Old 07-09-2007, 03:46 PM
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What props are you running? I have a brand new set of Mirage 19's that have never been used if you could use them.
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Old 07-11-2007, 12:46 PM
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Bobkatz,

Thanks for the input. May I ask if there was any particular reason for you running 2 right hand rotation props versus counter rotation? Also, what was the best mileage you got at cruise speed?

BajaFresh, I'm running 21P - 14" Turboprops. Just had them modified so I'm going to see how these do before making any further modifications.
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Old 07-11-2007, 01:52 PM
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Stott,

I bought the boat with two right hand drives & props and the boat was extremely reliable & fun the way it was. I never felt the time & dollars necessary to gain a couple mph's was worth it to me when what I had worked so well. I had friends w/blown Cigs, Fountains & Skaters and figured I would never run w/those guys so I went the reliability route. Personal choice nothing more. With that said, had I needed to replace a drive I would have liked to go counter rotating.

I love twin small block boats in the 26 - 30 ft range.

I have no idea of the fuel mileage. I can say it was much better than my friends above referenced boats. They were always B*tchin about fuel!

Add some pics, would love to see the boat, great memories!!

Do I recall that hulll having a hook in it?

Katz
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Old 07-11-2007, 02:41 PM
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Just for some comparison numbers:

I have a 1987 Baja Force 265;

Twin 350 mags w/ alphas (both standard rotation, which I believe was quite common in this age of boat);

speed on the "wishometer" is in the low to mid 60's, and running along other boats, this seems to be consistient;

I'm turning 5200 rpm w/ 20 dergree props (will upgrade soon to labbed 23's, as these engines are stamped with 4200 - 4600 max w.o.t.

Your boat may be a little heavier(?).

I'm about 5200 lbs. dry.
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