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Ordered My New Boat - 300x or 2.5 offshore- need advice

Old 09-09-2003, 11:21 PM
Join Date: Dec 2002
Location: chesapeake bay md
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Doug My truck will only get to that speed on the down side of the bridge. If you look close you will see it even develops a little water pressure. The recall will hold untill you turn off the battery. Now if I could get a hitch on a Viper.....
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Old 09-09-2003, 11:31 PM
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Torque= HP* 5252/rpm
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Old 09-10-2003, 09:06 AM
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The stock 280 (7750 rev limiter) has a one year warranty, the Offshore Race (8250 rev limiter) has no warranty, these motors are a different animal than the drag motors which are greater than 300 and 9000++++ rpm and NO warranty.

Be careful when comparing the 300 Pro Max to the 300X, they are totally different motors, the "x" being a lot more powerful, but have a 200 hr lifespan...............some a lot less, before they either SCATTER or require a rebuild, the 280 requires it around the same time. Reality is to tell you how long the motor will last is impossible, what you need to do is perform a leakdown test on the motor every once in a while and once it exceeds 8-10% it need to be gone through.

I have always heard about the 5-6mph difference (I have no hands on experience), but I can say that a well set up 2.5 will give them a run, and will perform better on the whole.

Anytime you modify the motors, Merc will not cover you.
It has been my experience (and a lot of guys around here) that merc will back out anyway saying that it is operator error................who woulda thunk?

As for getting more power out of a 280, it is rather simple, there are tuner mods, lighten and balance the pistons, wrist pins, and rods, add sportjet reed cages with there reeds, do a little rod slot work, and add an SVS, finally if you really want to get into them you can open up the porting a little, look to or www.diamond for power upgrades (there are others).......a motor like this will be MORE reliable than a stocker.......and run like a dream.

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Old 09-10-2003, 11:10 AM
Join Date: Nov 2000
Location: NJ
Posts: 560
Default Firewalker, you are right

I have been trying to get the point across that the 300X's and the 300 Promax are not the same motor! The term "300" keeps getting in the way with most of the guys, ( see my post #35). The P/M (promax) that were on my 28' and 32' Skaters (not the same pair of motors) were very reliable, and very different from the Technology in the X's. As you are aware of , the block, fuel injection, intake, piston etc. all different. I am sure that the X's might be a little more reliable on a 28' to 32' v bottom, then on a very light cat. 200 hrs? for the X's, I could only wish. The new 2.5's (alternator motor) seem very reliable and docile. fast and light. The 32' Skater with the X's is 5 mph faster then when the boat had the P/M engines. Same props, 500 rpm more,??? 30-35 Hp more then the P/m, don't know how much HP the P/M's developed, or the X's for that matter, but i do know the difference between the two. I would guess the P/M's were not putting out 300 HP, more along the line of 280-290 judging from the speed of a similar 28' Skater with the 280 2.5's. Granted the gear ratio plays a small part, but only in the lower ranges, and not on top. As far as the 32' is concerned, I don't know of any twin engine 32' Skaters with 2.5's to compare to. As far as I am aware of all twin 32's had either promax's or X's.
Mike Walters boat has been good with the promax's 109 for a 30' very good, The best I ever got out of the 28' Skater with the P/M's Spinning 14.5x32" 3 blade cleavers, Lab finished by Dennis Cavanaugh was 114, but this speed was not every day, not even close, late afternoon, cool air, running into 10-15 mph wind, small very close Bay chop, 1.75" up. 10 pounds water pressure almost empty fuel tanks. Every day, 107 or so. I always have better results with the 14.5 dia props, rather then the 15" I find i rather use the HP spinning the pitch rather then spinning the Dia. These engines had the small shafts, but on a 28' Skater the light weight kept the shafts from breaking, only broke one in 2 years, but I keep thinking the sand bar we sort of hit might have played part. The X.s with the big shafts, and the added weight of the 32' Boat have never broken a shaft. IMHO I think the 555 might be part of the problem! Why I would be holding a piston in my hand, just after it came out of the block, and plug into the 555 and it says, " everything A-ok" i DON'T THINK SO! This last little Burp must have stuck a piston. Ahh the joys of boating.

Once Again, go with the 2.5's, or find a pair of Promax's Hey mike, want to sell your mortors to Maximus?


Last edited by Philip; 09-10-2003 at 11:27 AM.
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Old 09-10-2003, 11:31 AM
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Philip, I have a 300 PM on a boat, and a few 2.5 powered weapons, I can tell you that the 300PM makes 285-90 hp, and the 300X looks to be making somewhere in the 320-30 range.
I have seen more than my fair share of 300X motors that I can stick arm in one side and out the other.....with under 100 was under 20.

If you are a wave chaser the only way to run is 2.5 motors, if you run glass, and only care about every last mph the X motors is the way...........but I think I could make the 2.5 scare or even beat the X, but it sure will run better in the rough and out accelerate in the calm, and possibly only loose on top........maybe.

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Old 09-10-2003, 06:20 PM
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Default Maximus

Maximus is running great. I got her down at the shop right now having everything gone through, and should have her back by friday. The port motor idles up real high and does not want to come down, probably the IAC, or a Mapp Sensor. Otherwise 109 +/- is the fastest Ive taken her, I belive she has alittle more in her, but im not ready to let her hang out any longer to find out yet. Everyone is diggin the boat on the west coast, it is definitely not the ususal Team Checkers BS we see out here so much. Maximus stands out like a soar thumb around the harbors. The harbor masters have given me allittle, I should say alot of **** due to noise and the fact that I have no registration, just the title. That will all get taken care of soon enough once AZ. sends me back a reg.

Mods on the 2.5's -
The guy running the 2.5's has done alot of **** to his motors. Pistons, Cranks, Portings, Exhaust, Reed Cages ( Something with the angles), and some tunning mods, not really sure what the costs where or how it effected long term reliablity but he says his motors scream now compared to before. The 2.5's would be the way I would go if I was building a boat with outboards. The motors have been around along time and have proven themselves over and over again. I have never been in a boat with 300X's only the 300 Promax, alot quiter and you could breathe the air around the boat on those cold starts. The 2.5's just get up and rev out.

Just my .02 - which is not worth much considering I have never owned any outboards.
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Old 09-10-2003, 06:43 PM
Join Date: Feb 2001
Location: houston tx
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Do the race motors have the shift cut out TX2 was talking about. I'm a newbie when it comes to Souped up sewing machines.

I'm getting mine rebuilt at lake x even as we speak. Not cheap to fix when you break them good. But alot cheaper than rebuilding a supercat motor.

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Old 09-10-2003, 08:52 PM
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I do not have what he is talking about just nutreal saftey switches. Mine are 99's.
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Old 09-10-2003, 10:53 PM
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Philip, You and Richie have to be experts on this topic. 300X vs 2.5
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Old 09-11-2003, 11:13 AM
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Join Date: Apr 2002
Location: Boca Raton, FL
My Boats: 38 Jupiter CC, Miss GEICO
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Default Supercat

Yeah I'm sure they are cheaper than the supercats

I'm starting to lean words 2.5's

Ok next big question.

TWO or Three. Should I set the boat up with triples?

Is there a market to resell a boat like that? I heard the center motor takes a beating?


I'll post pic's of the boat in the mold this afternoon. going up to the shop at lunch

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