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Discussion Starter · #1 ·
Last winter I purchased a 1990 Baja 240 It had a stock 310 hp 454 w/ a 17 pitch aluminum prop The boat would not plane out with more than 2 people in it and had a top speed of only 48 mph I changed it to a 20 pitch 4 blade SS It didn't help much I installed a custom Comp Cam, Comp roller rockers, dual plane intake, @ a set of large oval port heads ported & redone by my local engine builder The stock bottom end broke 2nd time out I had a forged 496 stroker short block built w/ 9.5 pistons It was the end of the season & didn't have time to dyno I would think this thing should make 500 hp The boat tops out at 61 mph on the gps @ 5300 rpm w/ a 26 pitch prop & has a tough time getting on plane w/ little weight in the boat. It still struggles to pull a wake boarder out of the water w/ a 1/2 tank of fuel and 4 people in the boat w/ the old 20p 4 blade prop Guys w/ stock 350 mags run circles around me this sucks! Whats wrong here?
 

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61 @ 5300 with a 26 pitch prop?? Your prop slip is not good at all. I think you need to make sure your rpms are accurate. I have a friend with a 24 baja with a 502 and a true 500 horse and it runs 68 mph @ 5000 with 24 4 blade bravo1. gets on plane fast and runs 68 all day.

I think you rpms are off and you need to pitch down to get on plane easier. Or you could have the wrong cam or someone butchered your heads. so many variables.
 

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Discussion Starter · #5 ·
I do alot of business with this engine builder The last sbc he built for me went 70mph in a 22ft Four Winns Only a pocket port was done on these heads the Cam Specs are .515/.520 Lift 224/230 duration @.050 114.0 lobe separation Besides the stock motor bearly got this thing to move Everone I talked to says this boat should do 60 mph stock (Maybe if you pushed it off a cliff) Could all my problems be w/ the prop? Also It doesn't have trim tabs How much would they help? If I figure the prop slip it's almost 30% I didn't think that was even possible If the tach is off it might explain some of it, It is a stock tach
 

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Discussion Starter · #7 ·
hump said:
Could the boat be waterlogged. You may be carrying a lot of extra weight. I had this happen to me.
The boat does sit pretty low in the water If you stop too fast the water comes over the engine hatch & onto the back seat. How much extra weight could we be talking about?
 

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you had the wrong prop on there to begin with. With the stock engine, you should have been running a 21 pitch ( or 22 pitch 4 blade) prop not a 17.
 

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You've been running the wrong prop from day one, 1st to small, now to large, the diameter of the prop come's into play also, not just the pitch. and it does sound like you have some unwanted weight in there somewhere too. do you have a weighing station around, like some quarry's, gravel pit, etc. they have them to check their trucks weights, then you can compare to what the boat should weigh. And your right about 350 Mag's too, I can pull your arms out of their sockets if I'm not careful.. :bigsmile:
 

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I had my rig weighed at a local semi-truck scale.
$8.50 total. They weighed the front & rear axles on the truck, and the trailer with it attached, then I went back without the trailer/boat and they weighed the truck by itself. Fast, cheap, painless.
 

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I had a '91 240 with the 454 Mag in it. The prop was a Mirage Plus 21 pitch worked over by Houston Propeller and would run 68-70 all day long.

Put a 21-23p prop on it for starters.

Also, unless you are in 2-4 foot swells, you should not have any water coming over the *** of the boat. Get a moisture test on the hull.

This is how it should sit in the water, full of fuel and beer.
 

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i feel you

if you have the same boat as Zen it is the same as my 1990 226 which was a 240 in later years.my 330hp went a top speed of 62 gps.i rebuilt motor with a dynoed 430 hp and the boat ran 68 gps with a labbed 23 mirage prop.at this speed the boat only had 10% prop slip which is very good for a boat that had 17% slip when i bought it.i also had a wet transom which i replaced.you maybe need to look elsewhere for your problems.i know a few people with bajas around the same year with transom problems.
 

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I agree, something strange here, does sound like waterlogged to me to...as stated before try taking somewhere and weight it...that should get a idea. do baja's use foam under the floor ?? my checkmate's got soaked, weighed a ton !!! Rob
 
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