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Discussion Starter · #1 ·
Hi guys, I have a few questions about my 1986 Formula 242 LS. Sorry about the long post, I am pretty desperate for some help.

I bought this boat about a month ago, with a blown motor. It came with a crappy 260 horse 5.7 and an Alpha one. I took the motor out and completely re-finished the bildge and transom plate. I had the drive re-built as well (1.5 ratio Alpha). I decided to keep the small block for $$$ reasons (maybe a mistake), and I bought a "Stage II" 350 from Jasper Engines' "high performance marine division". The motor is supposed to make 325 horsepower at 5400 RPM, and 370 ft/lbs. of torque at 3700 RPM. This motor has 4 bolt mains, all forged internals, Dart heads with 1.94/ 1.50 valves, and a nice healthy cam. I installed the re-manufactured long block with an Edelbrock Performer intake manifold, a 750 Q-jet from a Merc big block, a Holley marine high volume mechanical fuel pump, and all new GLM manifolds, 4" magnum risers, and spacers. It has open through hull exhaust into 4" Eddie Marine tips. I am using the Thunderbolt ignition set-up with the total timing at 32 degrees. I broke the motor in properly, and it sounds great. It just has no power.

I have tried 5 different props and can not get the motor to pull over 4300 RPM's. The best performance I have seen is with a Mirage 19 pitch prop. At 4300 RPM's, it is at 43 MPH on GPS. Deffinately a dissapointment...lol. I have tried 3 different size metering rods in the secondary's on the Q-jet, with no big improvements. I even tried an Edelbrock 600 marine carb, and it ran even worse. My last resort is to try a Holley 750 carb, because I think it may want more fuel. Does anyone have any ideas or advice for better performance? I hope I am not expecting too much, but I did hope the boat would do a solid 50 MPH??? I know it's a big boat for a small block, but I figured with 325 horse and 370 ft/lbs, it would run ok.

Any ideas or advice are greatly appreciated. I spent a ton of money and time, and I am pretty upset. THANKS!!!


Here is the link to my engine specs:

http://www.jasperengines.com/pdf/Chev-350-Marine-325-05.pdf
 

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I thought you had sold your Formula? Is this a new one?
Anyhoo, have you checked the fuelline coming from the tank?
Sometimes the anti drainback ball in the fitting at the tank will starve a higher performance engine.i had to remove the one in mine as it was pretty gummed up and I have read the same happening to a few on here that went to bigger engines.
Unless there is something very wrong with the engine I would go with something limiting fuel flow.

Only problem I found with a hi-perf smallblock in a big heavy boat is that if you prop it for speed it struggles to get on plane.
My boat ran almost as fast with a 300/350 as a 310/454 but getting on plane is 10x better with the big block.



Chaparral 21XLC Merc 502/Alpha
 

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try timing ay 36 at 3000rpm then pull the plugs get reading thaT will tell you how the motor runnig . use the holly it easy to change the jets
 

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Discussion Starter · #6 ·
Thanks for the replys guys....

What's happenin Frank, this boat is a new one, I just bought it, and immediately repowered it. I always wanted a 242-LS. I will check the fuel pick-up in the tank, that is one thing I didn't really look at. I did pump out all of the old fuel through the pick-up, and fill with fresh 93 octane fuel.

The timing is at 32 degrees total advance at 3500 RPM. That is what the techs at Jasper want it at. I did pull the plugs, and they are pretty white. That's why I decided to try a Holley 750. I bolted it on tonight, I will test it out on Friday, and report back.

Thanks again.
 

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i dial my 540 dart motor 600ponys . check my plugs they were white i went 3 size in prim 5 size in secd no power vale and gain 3.5 mph now my plug are looking good . so ther is hope for more speed good luck . and i always use gps so i no if i made more power
 

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Its in the fitting at the tank,its just a bb sized ball that is supposed to stop fuel from flowing back into the tank.
In some cases it will restrict flow. I would throw a fuelpressure gauge into the carb line temporarily and see what happens to the pressure when you run it. Just be careful , running low on fuel under load can kill your new engine quick.
You need to bring that bad boy down to Texas one day!
:)




randymbtech said:
What's happenin Frank, this boat is a new one, I just bought it, and immediately repowered it. I always wanted a 242-LS. I will check the fuel pick-up in the tank, that is one thing I didn't really look at. I did pump out all of the old fuel through the pick-up, and fill with fresh 93 octane fuel.
Chaparral 21XLC Merc 502/Alpha
 

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Can you get me the part# and manufacturer to that cam ? Reason why I ask is that it looks 'identical on paper' to the GM 5.7/290HP crate engine cam that is an absolute pig of a cam. Thus, why I need further investigation to see if actually the same or not.



axkiker - that line of Dart heads is made/sold as a replacement head that is stronger and a little more powerful than the factory replacements. A decent head for use up to low to maybe mid 300's hp level.

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In the meantime definately try the Holley. Also remember, it may need a little tuning for your particular engine. So don't totally base it's performance of first run. Check plugs and re-jet as necessary.
 

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cfm said:




axkiker - that line of Dart heads is made/sold as a replacement head that is stronger and a little more powerful than the factory replacements. A decent head for use up to low to maybe mid 300's hp level.


gotcha. Anytime I hear dart I think of full blown race stuff. I didnt know they made stuff for mild applications.
 

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Discussion Starter · #12 ·
OK, I checked the pick-up in the tank, and it looks real good. It dosen't have a check ball, it's just a long tube with a fitting on the end. I removed the line to the separator also, and it looks fine.

I bolted on a Holley 750 that I borrowed from a friend (just to try it out) and it leaks gas like crazy, so that's out. I need to find another carb, because I'm not going to spend $400 on a new one to realize that it's not my problem.

I am strating to think that I need to drop down to a smaller 17 pitch Mirage prop. Maybe the boat is too heavy and the motor is just lugging. I don't know if that explains why the plugs are white? Would overworking a motor cause it to be lean? I doubt it, but who knows.
 

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Discussion Starter · #13 ·
cfm said:
Can you get me the part# and manufacturer to that cam ? Reason why I ask is that it looks 'identical on paper' to the GM 5.7/290HP crate engine cam that is an absolute pig of a cam. Thus, why I need further investigation to see if actually the same or not.



axkiker - that line of Dart heads is made/sold as a replacement head that is stronger and a little more powerful than the factory replacements. A decent head for use up to low to maybe mid 300's hp level.

===================================

In the meantime definately try the Holley. Also remember, it may need a little tuning for your particular engine. So don't totally base it's performance of first run. Check plugs and re-jet as necessary.
Thanks for the good input CFM, I will call Jasper tomorrow and see if I can get the part number.
 

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What size lines are in your fuel system.Mine dropped down to 1/4 in and out on the separator and the pick up went through a 1/4 90.Looked good from the out side but not when I checked the inside dia.
 

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something is screwy.
Sounds like a fuel problem especially if plugs look lean.
Either that or they jacked you on the engine.
Cant imagine you would need a 17 pitch prop.
A stock 300/350 merc turned a 21 Mirage in my boat to 54mph
At 4000+lbs it isnt that far off from yours.


Chaparral 21XLC Merc 502/Alpha
 

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go to your local cheap auto store and but a $15 fuel pressure gauge. Install it right in front og the carb. If you're running into a fuel issue, the pressure may fal off a cliff when you reach your 4300 rpm wall. At least that way you know where to look for the problem.
 

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I might have the same problem to an extent. I have twin tanks and I recently just put in shut off valves in each line. I thought the internal diameter of the valves looked a little small. If "we" put a fuel pressure gauge on right in front of the carb, what are we looking for for pressure? Mine is a 7.4L btw.
 

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Discussion Starter · #19 ·
Well, I stepped down to a 17 pitch Mirage prop, and it made a huge difference. Now it turns 4800-4900 RPM's at 47 MPH on the GPS. It comes out of hole ten times better also. Now when I nail the throttle it actually takes off, and has some balls.

I think with some more timing and different metering rods, I can get a little more out of it. And I am having the bottom paint soda blasted, and hopefully that will help a little. Right now it has several cotes of old "shark white" paint on it, and it looks like crap. If I can get 50 MPH out of the small block, I will be happy.

Thanks again for all of the help and advice guys, I appreciate it.
 
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