Twin 5.0LXs - RPM stop @ 3000

bruppert

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Sep 9, 2003
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New Boater<br />I have a 32 foot 1995 Silverton 312 Sedan with twin Mercruiser 5.0LXs. Each engine is rated at 205 Hp. Rochester Carbs. Boat weighs approx 13,000 lbs. The boat was put in the water at the beginning of July. It does have a little growth on the outdrives so I would imagine it is also under the boat. It is kept just off the mid-Chesapeake bay near Baltimore... not salt water but nor fresh either.<br /><br />The problem is I can get it to run any faster than 10 knots. The RPMs will NOT go above 3000 on either engine. I just bought the boat and do not know how long it sat without running or being maintained. The port engine takes a little bit to starts, idles a little rough for 1 or 2 minutes then runs fine. It does NOT cough or backfire at any speed. Neither engine gives any problems at any speed. Oh, I do have the occasional problem of the port engine stalling when dropped into reverse but that may just be me getting used to it (Never owned a boat before). I have Silverton send me a spec. sheet and everything looks correct including the props. It said the boat should go 41 MPH using the 5.0Ls and I have the 5.0LXs which have 15 more HP each. The boat is going at approx. 25% of what is should.<br /><br />Does anyone knows where I should start? I am suspecting a Fuel issue.
 

snapperbait

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Aug 20, 2002
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Re: Twin 5.0LXs - RPM stop @ 3000

Clean the bottom, outdrives, and props first.... Just a little growth can make big issues.... Make sure the props have no damage... <br /><br />Clean bottom, fresh fuel, then go after the carburators for a rebuild and a full tune up on the engines... Oil change too... Spark Plugs, plug wires, distributor cap and rotor, points and condinser(if applicable)... While the distributor is apart to change the points, inspect the ignition advance mechanisms which consist of springs and weights... If they look rusty, replace them... Set the igniton timing to factory specs...<br /><br /> Belts, hoses, check em' and replace em' if they look bad...<br /><br />Good luck and happy boating.. :)
 

bruppert

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Re: Twin 5.0LXs - RPM stop @ 3000

Thanks a lot! That list should keep me busy for a couple days.<br /><br />I'll do it in stages then post back what I found to help the most.<br /><br />I didn't see fuel and water seperation filters on your list. I will definitely replace the fuel filters but what about the WS filters?
 

snapperbait

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Aug 20, 2002
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Re: Twin 5.0LXs - RPM stop @ 3000

Yep! Fuel filters and water seps too...<br /><br />New I was leaving something out... :)
 

Bondo

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Apr 17, 2002
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Re: Twin 5.0LXs - RPM stop @ 3000

Very Sound Advice Snapperbait.....<br />A 1995 will have the ThunderBolt Ignition System... No Points, No Advance mechanisms....<br /><br />I'd Start with a Full Engine Survey(Comp.test, leak-down, etc.).. Then the boat bottom... Then the lower shift cable on the motor/drive that Stalls on shifting....<br />Along with Snapperbait's list, you'll Either have it Fixed, Or Atleast Know What's Wrong.....
 

loadnet

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Aug 27, 2003
Messages
225
Re: Twin 5.0LXs - RPM stop @ 3000

I agree 150 percent with the Compression Test..<br /><br />I would for SURE start off with a compression test before you purcahse any parts at all..<br /><br />It's the cheapest way to find out if you have a real problem building up inside.<br /><br />If your compression is not up to parr you can throw tune up parts at that baby all week long and end up with the same poor running results you have at present.<br /><br />You may have engines that are pooped out in need of internal rebuild....<br /><br />Just my 2 cents if you want to save some tune up bucks..<br /><br />and do these engines rev up to specs in Neutral?<br /><br />PB
 

bruppert

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Sep 9, 2003
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Re: Twin 5.0LXs - RPM stop @ 3000

I am going down there today, haven't purchased anything yet. I am probably going to pull it out tomorrow.... Hurricane coming :( <br /><br />I will do a compression test first. Guess I'll have to run up Dad's to get a guage or buy one.<br /><br />Thanks again!
 
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