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  #1  
Old 10-15-2004, 04:27 PM
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Cody Cody is offline
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HP ratings for 351's + more

What was the HP rating for the 351's used in the 1991 prostars?

Mainly, I am looking for the most efficient ways to preserve the boat. What things are recommended to get the most out of it?

K&N filters?
Moblile one?
Synthetic oil?

Stuff like that.

Thanks and
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  #2  
Old 10-15-2004, 04:41 PM
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1991 Prostar should have a 240 HP engine. Changing the oil every 50 hours or at winterization is the rule. Motorcraft FL1A oil filter. In the spring replace the impeller. If you change your oil frequently, synthetic is a personal decision. Change transfluid every two years or 100 hours, same for h2o separator filter. Don't use armor-all use Formula 303 vinal formula. Wipe down your boat at the end of the day and keep a good coat of wax on it.
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  #3  
Old 10-15-2004, 05:00 PM
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east tx skier east tx skier is offline
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If you are talking about the "most" horsepower, I'd suggest, in addition to what George has recommended, an acme 3 blade prop. Also, soak your flame arrestor in some carb cleaner (let it dry out completely before reinstalling it). Sta-bilize your fuel when you're not going to run it through there in fewer than two weeks.
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Old 10-18-2004, 02:21 PM
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east tx skier east tx skier is offline
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Well, you got me thinking, and I didn't want to rehijack the other thread. I spoke with Richard at skidim this morning about ways for a guy with a 351 HO and an acme prop to squeeze some more horses out of his boat. His recommendations (which corresponded with JimN's) were to upgrade to the Edelbrock performance intake manifold and to have a good machine shop bore out the cylinders a bit for better compression.

So what was, at first, just a thought is now sounding pretty good. Can anyone with an early nineties prostar who has upgraded to the Edelbrock intake tell me if I have roomunder the motor box to do this (1.5") without dropping $70 on that slim flame arrestor that they have at skidim as well? What about boring out the cylinders; how expensive a job is that?
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To me, this forum is about love of inboard boats. It is about the sharing of information and, on a good day, some humor. It is not about post count, brand of boat, or any other superfluous labels that lend themselves to a false sense of superiority. Please, respect one another, try to pass on accurate information, and keep your eye on the ball.
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Old 10-18-2004, 03:00 PM
nattylightmike nattylightmike is offline
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I have a 90 prostar, I think that the engine covers are the same. Last winter I put on the edelbrock intake it fit fine. The only thing that I had to mess with was length of the linkage for the throttle cable. Performance wise it is hard to tell because I installed the intake, electronic ignition and rebuilt the carb all at the same time. Before I did any of this WOT was about 3900 rpm's and now it is 4600 rpm's WOT.

Last edited by nattylightmike; 10-18-2004 at 03:03 PM.
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Old 10-18-2004, 03:24 PM
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east tx skier east tx skier is offline
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Thanks for the reply, Mike. I'm not sure if the motorboxes are the same or not, but it's encouraging that you had room nonetheless. The estimation of horsepower bump that I got this morning was about 10 hp and a little more low end torque, but every little bit helps. I think I might see more gain out of boring out the cylinder chambers, but ya gotta start somewhere.
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Old 10-18-2004, 04:17 PM
rasmithaz rasmithaz is offline
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Hey nattylightmike....did you replace the holley with an edelbrock carb?
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  #8  
Old 10-18-2004, 05:08 PM
nattylightmike nattylightmike is offline
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After I put the new intake on I figured an edelbrock intake/carb combo would work better. So I put on a edelbrock 600cfm that my buddy had. It worked alright but I couldn't get it dialed in for the hole shot so I put the holley back on. It took me a while of messing with the holley but I finally got the hole shot I was looking for.
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  #9  
Old 10-18-2004, 05:14 PM
Storm861triple Storm861triple is offline
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In response to the above threads...

Boring out the cylinders to obtain more power is a terrible idea. Boring the cylinders is a SERVICE item, not a power improving item. You bore the cylinders when the wear to the bore is excessive, or when there is damage (scoring). The only (practical) way to repair this wear is to bore the cylinders to the next size that results in their being true, and installing appropriate sized pistons.

There may be a SLIGHT increase in power but we're talking maybe 5 hp...if that from the increased bore size. The cost if this is substantial (Probably at least $1000.00 unless you do all the labor your self), and it shortens the total servicable life of the engine; you are boring to the next "service" size before necessary, lessening the number of times left in the future.

If you want more power, it's a simple path. In order of bang for the buck, everyone on here should do:
Cam
Intake
Heads.

The cam will make the single biggest difference for the money(if you do it yourself), and a bigger difference than an intake ever will. You can get a new cam and lifters from Summit Racing for under $100.00! You can expect about 20+ hp from a mild cam. Easy.

The intake is the next place, at about $200.00, it's over twice the price of the cam, and it will net around 10-15 hp on an ontherwise stock motor. On a motor with the above mentioned cam, you'll see a slightly greater gain w/the manifold. The intake would come before the cam if you pay for the labor, as swapping an intake is an easy an relatively quick job.

The place offering the greatest restriction is the stock heads. This means that this is also the point of greatest total gain, stock or otherwise, if replaced. Not only will a GOOD, MODERN head increase power dramatically, it will also reduce emissions, and improve fuel economy. There is no down side or compromise to a modern head whatsoever, except for cost. Heads can be had for anywhere between $400 and $1500. depending on the head, and how you aquire them. You can get GT-40's or GT-40P's off ebay for around $400.00, loaded. Modern aluminum heads, such as Trickflow's, or AFR's run over $1000.00 brand new, but can be found in great condition used for less. Heads are going to make the biggest difference in hp and torque. On an otherwise stock engine, you could expect as much as 50 hp, but on an engine with a good cam and intake, a swap from stock heads to modern aftermarket heads could yeild as much as 100 more hp! This single component is why most of the new inboard engines make almost 100 horse more than the old 240 hp 351. (I know they're 350 Chevy's now but the reason for their power is in the HEAD! and the same goes for the Ford engine)

One last MAJOR improvement is to change the cam from a flat tappet to a roller cam, w/roller lifters. Like modern heads, a roller cam has a more modern and aggresive profile which allows the engine to make much more torque across a broader RPM range, compared to a flat tappet cam.

An AFR headed, roller cammed, 351w would have NO problem cranking out well over 350 lb-ft of torque and 350 hp, all below 5500 RPM. Check this link out, notice the second engine down. That's just a little 302. Our engines have another 1/2" of stroke putting the twist on things, and that little bugger is putting down OVER 300 lb-ft at only 2000 RPM! Think that would yank you up?...

http://www.airflowresearch.com/dyno/ford_dyno.htm

That power in an older MC would knock anyones sock off, and I would put money on it getting better fuel economy than our current stocker.

Please don't bore the cylinders unles they're worn out.

Last edited by Storm861triple; 10-18-2004 at 05:36 PM.
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  #10  
Old 10-18-2004, 05:49 PM
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east tx skier east tx skier is offline
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Storm, thanks for the info. As for the cam, I've heard that people have had problems with getting water in the cylinders after replacing the stock cam with something geared more toward performance. I'm not an engine guy, but can you think of any reason this may have occurred. I believe I've already got GT40 heads on my boat as it's a 351 HO (285 hp).

Thanks again.
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Red 1998 Closed Bow Ski Boat, Ford 351, 310 hp, Acme 4 blade, Perfect Pass SG.

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To me, this forum is about love of inboard boats. It is about the sharing of information and, on a good day, some humor. It is not about post count, brand of boat, or any other superfluous labels that lend themselves to a false sense of superiority. Please, respect one another, try to pass on accurate information, and keep your eye on the ball.
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