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08' Fountain 496HO Low RPM 's

Old 08-14-2017, 12:09 PM
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496 ho recommended rpm range is 4600 - 5000 rev limited comes in at 5150 / 5200 - apples to apples set up here --- one engine regardless is spinning within recommended rpm range and one is not. It has nothing to do with 5 blade MAX props unless those 2 props are not the same spec or one has issues.

Scanning info -- some fault codes are caused by other things and or other sensors in which those sensors or area can still be good. A lot of times no fault codes will show but available power will show 90 % or less %.

Regardless the engines need to be scanned and that scan needs to be studied properly, The engines need to be compression tested plus all lacking maintenance taken care of on top of.. Also ignition coils tested and wires - spark checkers do fine for that as well.

Fuel filters IMO prob really need to be changed. That's a once per year items and no one does that also spark plugs, wires, IAC muffler if applicable and so on as many things on the list for properly maintaining a 496.

Fuel injectors another area of 100 percent concern Since both engines are down on rpms from 5100. The 496 fuel rails can become internally corroded and that really messes up the fuel injectors. Common problem on the 496. .I see this weekly from cleaning / testing marine fuel injectors.

Last edited by BUP; 08-14-2017 at 12:17 PM.
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Old 08-14-2017, 01:25 PM
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Originally Posted by BUP
496 ho recommended rpm range is 4600 - 5000 rev limited comes in at 5150 / 5200 - apples to apples set up here --- one engine regardless is spinning within recommended rpm range and one is not. It has nothing to do with 5 blade MAX props unless those 2 props are not the same spec or one has issues.

Scanning info -- some fault codes are caused by other things and or other sensors in which those sensors or area can still be good. A lot of times no fault codes will show but available power will show 90 % or less %.

Regardless the engines need to be scanned and that scan needs to be studied properly, The engines need to be compression tested plus all lacking maintenance taken care of on top of.. Also ignition coils tested and wires - spark checkers do fine for that as well.

Fuel filters IMO prob really need to be changed. That's a once per year items and no one does that also spark plugs, wires, IAC muffler if applicable and so on as many things on the list for properly maintaining a 496.

Fuel injectors another area of 100 percent concern Since both engines are down on rpms from 5100. The 496 fuel rails can become internally corroded and that really messes up the fuel injectors. Common problem on the 496. .I see this weekly from cleaning / testing marine fuel injectors.
BUP, thanks for the tips. I wish you were more local. I'm in Brooklyn NY. Your analysis seems spot on.
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Old 08-16-2017, 09:09 PM
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Originally Posted by BUP
496 ho recommended rpm range is 4600 - 5000 rev limited comes in at 5150 / 5200 - apples to apples set up here --- one engine regardless is spinning within recommended rpm range and one is not. It has nothing to do with 5 blade MAX props unless those 2 props are not the same spec or one has issues.

Scanning info -- some fault codes are caused by other things and or other sensors in which those sensors or area can still be good. A lot of times no fault codes will show but available power will show 90 % or less %.

Regardless the engines need to be scanned and that scan needs to be studied properly, The engines need to be compression tested plus all lacking maintenance taken care of on top of.. Also ignition coils tested and wires - spark checkers do fine for that as well.

Fuel filters IMO prob really need to be changed. That's a once per year items and no one does that also spark plugs, wires, IAC muffler if applicable and so on as many things on the list for properly maintaining a 496.

Fuel injectors another area of 100 percent concern Since both engines are down on rpms from 5100. The 496 fuel rails can become internally corroded and that really messes up the fuel injectors. Common problem on the 496. .I see this weekly from cleaning / testing marine fuel injectors.

Hey BUP,

My mechanic came today and scanned the motor. Cylinder 3 had the spark plug cap off. Though it must of been off for a while because the spark plug was dead. We installed a new plug. Took boat out and both engines ran equal. Hit 5050 RPMs on both. I can't ask for more then that. I'm very happy. GPS 82MPH.
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Old 08-17-2017, 04:11 PM
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Originally Posted by BUP
Scan the engines and look for guardian mode faults - then look at available power in the scan --- I bet its showing like 90 % or 89 % or maybe even less for available power.

Balance props and repaired on top of ?? Bad rebuilt ? Or some form of prop issues after prop work ??? any current prop damage,

or low compression of that engine.

bad coils / and or spark related issue - possible spark plugs and or wires

scan tool is needed for sure

If you are DFW Texas let me know, .I have everything
Well it was in the first post of mine --- past midway down.

"bad coils . and or spark related issue - possible spark plugs and or wires "

Glad it is fixed.
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Old 08-17-2017, 04:13 PM
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THANKS FOR THE UPDATE always like the updates with what fixed the problem running issues.

Last edited by BUP; 08-17-2017 at 05:11 PM.
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Old 08-17-2017, 05:13 PM
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If I had to guess for a spark plug being not connect at the spark plug --------- WAS IT NUMBER 8 SPARK PLUG WIRE ? that would be my guess. number 8 is not uncommon to come lose and or unconnected.
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Old 08-17-2017, 07:47 PM
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I had a plug crack the porcelain and compression snuck through the plug and kept blowing the cap off most of the day.
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Old 08-18-2017, 11:57 AM
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Originally Posted by Smokin_Joe
Hopefully someone can help or point in right direction. I have an 2008 Fountain 35 Lightning with staggered 496HO. My port engine gets 4750RPM and my Starboard engine is only getting 4450 RPM. I'm only hitting low to mid 70's. I have Maximus 5 bladed props with 31P that were just balanced. Any insight will help.
Never mind. See its fixed.
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Old 08-21-2017, 07:53 AM
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Originally Posted by BUP
If I had to guess for a spark plug being not connect at the spark plug --------- WAS IT NUMBER 8 SPARK PLUG WIRE ? that would be my guess. number 8 is not uncommon to come lose and or unconnected.
I recently purchased this boat. I think the surveyour when completeing compression tests never re-installed cap.
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