5.0 mpi won’t plane intermittently

Guy boater guy

Recruit
Joined
May 28, 2020
Messages
1
5.0 Merc mpi bravo 1. Motor intermittently does not have power to get on plane. Last season it happen a couple times now it’s almost all the time. As it gets hot it runs better and takes off fine. On launch sometimes it hits a wall at 3k rpm and won’t go past. No miss or sputter. If you can get on plane it runs great. 5k rpm 43-44 mph and will run as long as you want. When you stop it won’t go again. Started very sporadic but now is almost all the time. Gas is good, prop is good, Hull is clean, fuel filter is new, motor shows no active codes, and ran on a different gas tank and same problem. Questions are, will tps or map sensor show codes when scanned and is there any chance a failing battery could cause power loss under a load? And what all components will not show an active code when scanned? Going in the next couple days to check fuel pressure and compression but seems like these issues would show a code.
 

tpenfield

Moderator
Staff member
Joined
Jul 18, 2011
Messages
18,477
Yes, have the mods move this to the Mercruiser forum. Probably going to need the diagnostic computer hooked up to see what is really going on when the engine won't go over 3K rpm with load.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
51,363
most problems wont throw a code, you must compare what the computer is reading to what it should be.
 
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