hurleyr

HELP! I have a 525 EFI that has a high speed sputter.

Runs killer for aboout 20-30 minutes up to 5k RMP. After sitting for a while then can't get over 4500 RPM without sputtering. Sounded like a fuel problem given that the boat sat for a while prior to my purchase. Runs fine below 4500.

The boat only has 80 hours so I didn't want to mess around.
Thus far have replaced fuel, water separator, filter, and fuel pump. Also, has new plugs. Old ones looked fine.

I was told the older 500s and 525s need valve spriongs around 100 hours. However, according to merc this motor already has the new valve springs. Could this be the problem or should I be looking at injectors? Or something else?

Any help on this is greatly appreciated.

Rob....

skopi55

Not sure what your issue is but I can tell you that the valve springs don't need to be replaced until around 300 + hours depending on how you treat it.

hurleyr

Valve springs was my last thought. Especiallly, since this motor has the newer version springs.

I'm thinking I need to hook up a scan tool to see if any codes come up.

hurleyr

OK, I just thought of something. I didn't replace the mechanical fuel pump. Could this cause this type of problem? Its not leaking.

On the fuel side, everything but the mechanical fuel pump and injectors have been replaced.

UNSANE

I was thinking fuel pump as well. What I know about EFI engines is that they need alot more pressure than carbs. Also you might want to think about the raw water impeller. Those definitely should be serviced every 100hrs or so. I did mine at 150 and it was "getting there". It's a big wknd with the Jax poker run so you might want to give it a couple of days for the experts to opine.

hurleyr

Thanks for the help! I think I found the problem. Pulled the gear housing and it was full of a gas/gear oil mixture. Looks like the mechanical pump was leaking on the inside.

I'm planning on putting in a new mechanical fuel pump next. Probably should have checked this first. I think this will do the trick. Oh well, can't hurt to have new fuel, pumps, and filters.

I'll post the results in hopes of helping any others with this issue.

Good advice on the water pump impeller. I plan to do a full 100 hours service which includes this part. The boat only has 80 hours but I'm not sure of its maint. history. I might just throw new plugs in her as well. Just to show there's no love lost.

hurleyr

Mechanical Fuel pump did not fix the problem. Thus far have replaced water separator, fuel filter, both fuel pumps and gas. The only thing fuel related not replaced is the injectors.

I have a better explaination of the problem:

Idle out of harbor runs great.

Open up till 5k RMP runs like a champ. After about 1 minute starts intermittent sputter. Sputters less at less RMP. Stops sputtering completely below 3500 RMP. I can run all day below 3500 RMP with no problems.

If I stop for a while and take off acceleration is awesome. After less time than the first pass it starts to sputter at a lower RMP +/- 4k RMP.

I have shook all wires while running and cannot get the problem to re-occur.

I plan to take it to Alexi at Boost Power tomorrow and have the codes run. Sounds more and more like electrical.

hurleyr

I forgot to mention the problem seems to be worst after full warm up. Or, the longer its run.

hurleyr

Gauges and tach stay rock solid during this problem.

Ted G

iTrader: (1)

I am going to guess coil going bad. Is it hot after running hard??