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496ho throttle issue

Old 10-09-2021, 09:55 AM
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Default 496ho throttle issue

Hey Fellas, first post and glad to be on a message board.. Big on automotive forums as im into cars.

I have a 2004 formula 330SS with twin 496s- recently the boats starboard engine has been limiting my RPM to 3500 at full throttle on the stick. its been my first season with a boat and got familiar with it in July and have had no issues, seemed that this once happened on a short trip a while ago but corrected it self the next drive?- Not sure which direction to go first , read about drive syncs and misfirings causing the throttle cut, does anyone know what diagnostic tool I can get and where to connect? Only had the boat for a few months and barely anytime for anything but going to try to dig through the owners manual for a obd type connection for a diagnostic tool? Any leads or recommendations fellas would be greatly appreciated rep points for any replies and help thanks!
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Old 10-09-2021, 11:52 AM
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Does The engine hesitate & sputter but stays @ 3000rpm? Easy check First, Remove the throttle cable from the throttle body. Then at the helm throttle push all the way forward. WOT. Now manually open the throttle body so the butterfly is vertical, fully open. Does the cable and throttle arm align up? Or is the cable short?
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Old 10-10-2021, 01:28 PM
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Okay, so it was easier for me to take airfilter off and look straight at the throttle body, and under full throttle the plate was opened fully, I cleaned the throttle body and it revd up to 4500 rpm no issue, I'm wondering if its an issue when in gear and motion.
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Old 10-10-2021, 01:43 PM
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Reving in neutral has nothing to do with in gear and under load. Takes very little air fuel and spark energy to redline in neutral.

Scanner , fuel psi tester, spark tester, multimeter are a dyi / mechsnics best friend.

Last edited by SB; 10-10-2021 at 01:58 PM.
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Old 10-10-2021, 08:54 PM
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What kind of scanner can I use and where is the port to connect? I can have a fuel pressure gauge is there a line to quick connect to get pressure? Also would like to put new coils and plugs this week as I have not done any maintenance to this unit besides oil and an outdrive+ cables. I have power probe and multimeter but not sure why one engine would be only pushing 3500 rpm is that the safety cut off? Also thanks for the replies and help fellas- First year with the boat and would like to cancel out my marina technician as much as I can. Thanks!!
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Old 10-10-2021, 09:38 PM
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Possibly guardian mode from over temp? Second guess would be fuel related due to that era of cool fuel pumps. Check fuel pressure at idle and while underway. Then monitor fuel pressure drop after turning the engine off. My money is on the fuel side due to the year of that engine.
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Old 10-10-2021, 09:59 PM
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Okay for sure sounding more like a fuel issue. Going to dig around a bit but each engine should have 2 fuel pumps (high and low)? Also hoping there inline and not in tank? Thanks again for all the help fellas rep points!
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Old 10-11-2021, 07:43 AM
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Originally Posted by mavallone997 View Post
Okay for sure sounding more like a fuel issue. Going to dig around a bit but each engine should have 2 fuel pumps (high and low)? Also hoping there inline and not in tank? Thanks again for all the help fellas rep points!
Front starboard side of the engine down low. You can pull the filter out of the cool fuel and check for debris. Has a black handle on top and a couple small screws holding it down.
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Old 10-11-2021, 09:33 AM
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Originally Posted by mavallone997 View Post
Hey Fellas, first post and glad to be on a message board.. Big on automotive forums as im into cars.

I have a 2004 formula 330SS with twin 496s- recently the boats starboard engine has been limiting my RPM to 3500 at full throttle on the stick. its been my first season with a boat and got familiar with it in July and have had no issues, seemed that this once happened on a short trip a while ago but corrected it self the next drive?- Not sure which direction to go first , read about drive syncs and misfirings causing the throttle cut, does anyone know what diagnostic tool I can get and where to connect? Only had the boat for a few months and barely anytime for anything but going to try to dig through the owners manual for a obd type connection for a diagnostic tool? Any leads or recommendations fellas would be greatly appreciated rep points for any replies and help thanks!
I personally used the Rinda to troubleshoot and verify engine parameters. You can also test injector function with the tool as well to determine if your engine is down a cylinder while under load. There may be better ones out there but this one has worked well for my needs. The connection is on top the engine with a dummy plug cap on it.

https://www.rinda.com/marine/mtspec.htm
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Old 10-19-2021, 09:27 AM
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What’s the verdict?
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