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30L Alpha 1 low RPMbs at WOT

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"I recently purchased a 2003 S

"I recently purchased a 2003 Stingray 180LS runabout. It has a 3.0L Alpha power package installed with 120hrs on it. It is in like new condition. The boat company and other owners of the same model say that I should be able to spin a 21" 3 blade around the 4600 to 4800 mark. I could only get 3700 out of it with a 21". Went down to a 17" SS and can only touch 4300. Confirmed tach was correct w/ shop tach and it is dead on. Checked each spark plug to see health of engine and each one was fantastic. Engine runs/sounds extreamly good, no knocking, pinging, missing bogging or anything. Checked the timing using the special procedure outlined in the shop manual and it was spot on. Throttle cable is extening all the way and opening carb all the way as well. What am I missing? Is there such thing as a govener on this engine? I can not think why I can not get the RPM's out of this thing. How are others getting 4800 out of the same boat/engine package? Any thoughts would be wonderful.

Thank you!!!!"
 
"No governor is used. You mig

"No governor is used. You might have excessive load in the boat, water in the double bottom, a rough bottom, incorrect trim, etc. My 19 Bayliner with that motor hit 45 mph at 4,800 rpms with the 'good' prop. With the 'junk' prop (that tried to mill a few rocks) it oversped at 5,000 plus--the diameter was reduced (by my grinder) at least an inch in dia as I "repaired" it.

Check the double bottom.

Jeff"
 
"Boat spec says dry weight app

"Boat spec says dry weight approx 2200 lbs. I estimate with full fuel, 21gal , batt. and gear. 2500 lbs. I weigh 125lbs. Boat bottom is clean never stored in water. No water in hull, dry as a bone. Always stored in garage. Getting within 3/4" of max allowable trim with trim cylinders, 20" extention when measured from center eye to center eye on trim cylinders, max is 20.75", according to Merc. shop manual. trim limit switch is set to max movemenent. prop is brand nre Merc SS prop. 14.5" x 17P Vengence. Boat truly runs good. Engine does not even sound as if it is being held back, ie.. does not sound as if it is loading up, sounds like she is stretching her legs with no problem. Good power coming out of the hole. Gets good gas millage. I normally cruse at 2800 to 3200 RPS and she just purs along at 30 to 33 mph. At 4300RPM hitting 44.5mph on GPS. Perhaps when it was built they put too much resin in the mold??? I'ver heard of this hapening once in a while, but normally in very large boats such as crusiers. Perhaps I should just learn to live with it and be happy with my "new used boat". I'm getting tired of worring about it."
 
"Frankly, it's working ver

"Frankly, it's working very well, but if you want a bit more rpms out of it, you might get the prop repitched. If it's aluminum, you could get up to 2 inches of pitch removed.

Jeff"
 
Jeff:

Thank you for your in

Jeff:

Thank you for your input. I'm taking the prop over to a custom prop shop this afternoon and they are going to do some slight re-work on the diameter it to find 200 to 300 more RPM's out of it. Looks like they will reduce the dia. down to 14.25" to 14.0." I would just feel better having the engine capible of getting into the middle of its WOT. I normally do not run it at WOT. Most of the time I only run between 2800 and 3200. I just like thing to be able to run around the Mfg's Specs.

Thanks again!
 
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