Engine cuts out/bogs down at higher RPM's

Cincy Aquaholic

Cincy Aquaholic

Active Member
Mar 15, 2009
1,329
Cincinnati
Boat Info
290 SS - 2016 Ford F250 Powerstroke
Engines
Twin 5.7 with Bravo 1's
My port engine recently starting cutting out and losing RPM's at higher RPM's. Symptoms are:

-Starts and idles fine and smooth
-Cruise at lower speed with no issue
-Cruise at higher speed for 5 minutes or so then engine cuts out and RPMs fall from 3500+ (range when this occurs) to 1000 then back up and down.
-Doesn't seem to sputter or backfire
-Seems like fuel starvation. Its not affecting my starboard engine so I doubt its the fuel its self.

Where to start? Fuel filter? Fuel pump?

Tips on changing the fuel filter on the 5.0? Looked like it was hidden in some housing. Will it be under pressure?

Thanks in advance.
 
Same engine, same problem. Replaced the inline fuel filter as it became defective. Problem fixed. I actually bought the filter from Autozone (auto version) for $12 as well as the $55 marine version. Stick with the marine version on this one. You can see the design and quality differences just be looking at them side by side.

The filters are usually mounted on the stringers somewhere in front of the engines. Turn the fuel pumps off. You'll have a litle fuel leakage but not too much. Put an absorbing mat underneath. You'll need a couple of box wrenches, red threadseal and teflon in a can sealant if I recall.
 
gerryb said:
Same engine, same problem. Replaced the inline fuel filter as it became defective. Problem fixed. I actually bought the filter from Autozone (auto version) for $12 as well as the $55 marine version. Stick with the marine version on this one. You can see the design and quality differences just be looking at them side by side.

The filters are usually mounted on the stringers somewhere in front of the engines. Turn the fuel pumps off. You'll have a litle fuel leakage but not too much. Put an absorbing mat underneath. You'll need a couple of box wrenches, red threadseal and teflon in a can sealant if I recall.
Click to expand...

Are you talking about this filter?
http://www.mercruiserparts.com/Show...8/10.png&inbr=2709&bnbr=110&bdesc=FUEL+FILTER
 
I have a 1987 410 aft that has had similar problems.
My marina does not add ethanol to the gasoline, and my problems began when I filled up at a distant marina. change of fuel filters did the job. My marina indicated that the problem may very well reoccur and I should be prepared to change filters periodically.
 
Cincy Aquaholic said:
My port engine recently starting cutting out and losing RPM's at higher RPM's. Symptoms are:

-Starts and idles fine and smooth
-Cruise at lower speed with no issue
-Cruise at higher speed for 5 minutes or so then engine cuts out and RPMs fall from 3500+ (range when this occurs) to 1000 then back up and down.
-Doesn't seem to sputter or backfire
-Seems like fuel starvation. Its not affecting my starboard engine so I doubt its the fuel its self.

Where to start? Fuel filter? Fuel pump?

Tips on changing the fuel filter on the 5.0? Looked like it was hidden in some housing. Will it be under pressure?

Thanks in advance.
Click to expand...
http://www.mercruiserparts.com/Show_Pictures3.asp?dnbr=884717003&ivar=images/COMMON/18403.png&inbr=12840&bnbr=70&bdesc=Fuel+Supply+Module%28Bravo%29

I believe this is what you have on your boat. The filter is inside. It will look like this link shows. Run your engine serial # to verify correct part numbers.
 
Woody said:
http://www.mercruiserparts.com/Show_Pictures3.asp?dnbr=884717003&ivar=images/COMMON/18403.png&inbr=12840&bnbr=70&bdesc=Fuel+Supply+Module%28Bravo%29

I believe this is what you have on your boat. The filter is inside. It will look like this link shows. Run your engine serial # to verify correct part numbers.
Click to expand...

You are correct. Thank you. I pulled the one on the motor that was giving me trouble and it had some nasty gunk in it. The other was just discolored. Replaced them both. $55 each. I'll be taking it out later and will report back if it's been fixed.
 
Update- well, changed the filters and the boat ran great . . . for one day. Then, following day same symptoms and in fact even worse! If I didn't pull the throttle back all the way when it started to lose RPM's it would drop all the way down and stall. Engine began to immediately cut out above 2500 rpms and couldn't get back up on plane. I had to limp home at just above idle. Still seems fuel starved but clearly more so than before. Or, to me, it may seem electronic in nature. Is there a throttle position sensor on Mercs like there was on my volvo? Could it be related to the shift cable issue that I have in that engine which makes for harder shifting which the dealer was planning to look at when it was pulled for the winter?

No alarms going off. Starts and idles fine. Runs fine until I try to get up on plane than within a couple seconds it will die.
 
Last edited:
Definitely a fuel problem, I had a similar one last week. Mine was a faulty check valve on the fuel pickup from the gas tank. You can check the thread "gradual power loss, then wouldn't run" to see how it went for me. There may also be a screen on your fuel pickup in the tank that is clogged, mine was.
 
I'm watching this one too.I have some old gas in mine but she starts immediately and runs good til just about2k or and then she falls on her face...get off the throttle and she is fine.

I'm going to pull my fuel and my filter.It's just hard for me to accept that 4yr old gas would fire right up and idle for an hour no sweat.I have to pull about 60 gals so not like it's nothing.

94 290da 7.4 BIII.
 
I'd check the filters again. There may have been enough contaminants in the tank to foul the 2nd set of filters as well as the first.
 
skibum said:
I'd check the filters again. There may have been enough contaminants in the tank to foul the 2nd set of filters as well as the first.
Click to expand...

Yeah, I think I'm going to pull that filter and see what's in there. I thought it was strange for it to run great for almost the whole day after I changed it then crap out on me. I'm starting to get suspicious of the fuel pump because of how erratic it was. Boy, did this put a damper on an otherwise awesome weekend of weather.
 
I had the exact same problem. It was the check valve in the gas line. Had it replaced and I have had no problems since.
 
sandysage said:
I had the exact same problem. It was the check valve in the gas line. Had it replaced and I have had no problems since.
Click to expand...

never knew there was a check valve in the fuel line, on the vent line maybe, (let's air in but doesn't let fumes out). a way to check this is run with the fuel cap off. I've seen this on jetskis as the vapor space must be replaced by air or you pull a vacuum on the tank which restricts fuel flow.

ETA: This only holds true on a single engine boat i.e. if you have a twin and only one is showing these symptoms, then obviously it's not the check valve.
 
Last edited:
The check valve we are talking about is not the one that vents the fuel tank, it lets fuel get pulled out but not flow back in through the pickup tubes. If there is a fuel/water seperator (i was told) the valve will be in there. If not, it will be near the top of the fuel tank, manybe on it like mine was. I switched fuel lines to check for it and the problem followed the one fuel line.
 
berth control said:
The check valve we are talking about is not the one that vents the fuel tank, it lets fuel get pulled out but not flow back in through the pickup tubes. If there is a fuel/water seperator (i was told) the valve will be in there. If not, it will be near the top of the fuel tank, manybe on it like mine was. I switched fuel lines to check for it and the problem followed the one fuel line.
Click to expand...

do you have a link showing the part? I've tried to find it on the Mercruiser site but have been unsuccessful. I'm having a similar issue, it started after my mechanic removed the HPFP and the Water separator assembly to install the seawater pump. I never did that before. I changed the water separator and the boat ran better, but at high RPM's it still drops RPM's. I ordered a new fuel filter as I've never changed it and the boat is 6 years old. I've had it for 4 of those years.
 
One of the guys at my marina with a '94 270DA was having a problem getting above about 3200-3400 rpm. He changed the spark plugs, but that didn't fix it. I told him that a lot of folks on CSR had fuel supply related problems preventing them from hitting WOT, so he started pulling fuel lines looking for an obstruction. Well, he removed the line feeding the carb on his 350 Merc to see if there was a filter or something where the line attaches to the carb. No filter, but he did pull a small, round screen from inside of the metal supply line where the flange is at the carb. It looked like a water faucet screen that someone had rolled around a piece of 1/8" dowel, making it into a small cylinder. He put everything back together without it and it ran fine. Do you guys think that this screen was part of that check valve assembly that just worked its way up to the carb attachment point?
 
Maybe the original owner shredded the bimini boot you were missing at the time of sale, and stuffed it in the fuel tank.:huh:
 
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