Mercruiser Engine '96 RPM drops to +/- 2900 rpm after one hour

leogetz

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Jul 23, 2004
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3
Hi All,<br /><br />Here's a problem from the Netherlands..<br /><br />I've a '96 Celberity 200SS with a Mercruiser 4.3 v6 alpha 1 LX. 190 HP , run for 250 hours now.<br /><br />The problem is , that it drops in RPM after about 1 or 2 hours driving. This first hour(s) it runs fine, about 5000 RPM , 45 mph.<br />After that it wont go higher than about 3000 RPM. If I stop and wait for about 15 minutes it goes fine again for another 30 minutes and so on.<br /><br />Does anyone have ideas about this ? <br /><br />Thanks in Advance..<br /><br />Leon
 

Bob_VT

Moderator & Unofficial iBoats Historian
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May 19, 2001
Messages
26,084
Re: Mercruiser Engine '96 RPM drops to +/- 2900 rpm after one hour

Welcome to iboats! Sometimes that indicates a coil starting to go. They are affected by heat and I have seen them go bad only when hot.<br /><br />Bob
 

lindb40530

Seaman Apprentice
Joined
Jun 25, 2004
Messages
40
Re: Mercruiser Engine '96 RPM drops to +/- 2900 rpm after one hour

Could be a clogging fuel filter. You might have sediment in the tank that gets pulled into the fuel filter. After a while of running they build up and clog the filter. When you shut it down, the gas runs back partially unclogging. I would replace the filters, and check the tank.
 

leogetz

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Jul 23, 2004
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Re: Mercruiser Engine '96 RPM drops to +/- 2900 rpm after one hour

Thank you for replies, Lindy and Bob.<br /><br />Bob, I'm dutch , and can't figure out what you meaning with 'coil'. Is there another way to explain this ? (sorry for my bad english..)<br /><br />Linday, where do you think those filters are hide ? Near the tank, or near the engine?<br />And is there a way to check the tank, since I thought you can't open them ?<br /><br />Thank you all very much!<br /><br />Leon
 

Bondo

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Apr 17, 2002
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Re: Mercruiser Engine '96 RPM drops to +/- 2900 rpm after one hour

Well Leo,<br /><br />I don't speak Dutch either......<br /><br />But,<br />If you don't know What the Coil Is,<br />And,<br />Can't find the Fuel Filter ,<br /><br />I Think you Need a Mechanic,<br />Not a Translator..........
 

akriverrat

Chief Petty Officer
Joined
Oct 31, 2002
Messages
588
Re: Mercruiser Engine '96 RPM drops to +/- 2900 rpm after one hour

an hour at 5000 rpm? TWO hours? it just needs a break. what is the wot range on a 4.3?
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: Mercruiser Engine '96 RPM drops to +/- 2900 rpm after one hour

hello<br /> on an american boat there is an anti-siphon valve on the tank. some tanks have a fuel filter in the draw tube for the tank. does you hull have a water seperating fuel filter? also if its EFI it will have filters that can clog. any alarms or other abnormal indications> I am almost with bondo. you may get in over your head if your not careful. the Coil is the inductive transformer that uses a collapsing primary magnetic field to induce a high voltage field across the secondary windings.<br /> its can give problems occasionally
 

hoot

Chief Petty Officer
Joined
Sep 8, 2002
Messages
434
Re: Mercruiser Engine '96 RPM drops to +/- 2900 rpm after one hour

the coil on boats is a cylinderical object, about 15cm long, 6cm in diameter. it has two small screw posts on one end and a larger hole in the middle with an ignition wire stuck in it coming from the distributor. it should be mounted close to your distributor, the plastic looking thing with 7 wires stuck in it running to the spark plugs and coil.
 

bomar76

Lieutenant Commander
Joined
Jun 27, 2002
Messages
1,963
Re: Mercruiser Engine '96 RPM drops to +/- 2900 rpm after one hour

If he runs that mill for an HOUR at 5 grand, maybe the next hour the valves are trying to catch up!!! :rolleyes: :) :confused:
 

leogetz

Recruit
Joined
Jul 23, 2004
Messages
3
Re: Mercruiser Engine '96 RPM drops to +/- 2900 rpm after one hour

The problem is fixed. On the tank, there;s bullit which keeps the fuel on pressure, so that the fuel pomp doesnt need to fill the complete fuel drain again each time. This 'bullit' was stuck a little. After removing this pain in the *** it runs like hell again! Thanx for the tips..
 
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