Mercruiser 5.0l MPI dont rev out?

[Memike]

Hi. I have some problems with my Mercruiser 5.0l MPI engine with Bravo III transom, everything from 2002. The engine feels tired and does not rev out. This only came after the boat had been in port for a week without being used. I only get my boat (Sea Ray 240 Sundancer) at 25 knots and about 3300rpm. Haven't started troubleshooting yet but wonder if more have had these problems? And can give me some tips of what to search for? And can be. Thought to start by changing the spark plugs if it doesn't help, check the fuel filter (new this year) then replace the ignition cables, fuel pump, inline filter, etc. But does anyone here have any tips? Sincerely

 

[Captn TJ]

What was your top speed and rpm beforehand? I assume you keep it in the water? What does the bottom/outdrive look like? Lots of growth/barnacles on the bottom?

As an FYI our 280 with 2/5.0 cruises at around 25/3400 rpm. However it tops out at substantially higher speeds - 40's mph.

 

[scoflaw]

Start with a full tuneup. Check compression while you have the plugs out. Check fuel pressure at the 3300rpm

 

[Memike]

What was your top speed and rpm beforehand? I assume you keep it in the water? What does the bottom/outdrive look like? Lots of growth/barnacles on the bottom?

As an FYI our 280 with 2/5.0 cruises at around 25/3400 rpm. However it tops out at substantially higher speeds - 40's mph.

The topspeed was nearly 30 knots, so not so not good enough. The propeller is new, the outdrive is freshly painted and the boat ground polished and painted under without any fouling.

I have order new inline filter, fuel/water seperator and spark plugs.

I wonder if it Can be that the ignition wires are changed. Is anybody having the right position diagram for a Mercruiser 5.0 MPI engine frome 2002 or know were to find it?

 

[Lazy Daze]

What's (or what was) your max RPM? You should be able to get well into the upper 4K range and the top speed should be 40-ish mph (35 knots). Are you trimming the drive as high as you can go? Or just partway?

If you're operating it correctly, there's definitely an issue - both now and before. Whether it's something simple or something much worse will take some figurin' out. If you google for mercruiser 5.0L MPI firing order, you should find plenty of info. Heck, if you google for GM V8 firing order, you'll find it, too. I don't know if you have the round dist cap or the crab style, but the crab style just saves space. Many of the dist caps have the cylinder numbers printed on them, by the way.

 

[Soulshine]

The firing order for that engine is:

1-8-4-3-6-5-7-2

 

[Memike]

Update:

Now I have changed the inline filter, the water separation filter, the spark plugs (witch looks good) and checked that the ignition wires are in the right lit order. But it behaves the same way anyway. So now i have ordered new knock sensor and map sensor and will check comp in all cylinders. This is a really annoying error.

I'll be back (like Arnold would say) in the thread about the error when I Have try out thoose things to.

 

[scoflaw]

New cap and rotor and if those plug wires are over 10 years old, get rid of them and don't buy a $20 set off ebay

 

[Memike]

New cap and rotor and if those plug wires are over 10 years old, get rid of them and don't buy a $20 set off ebay

I dont think this is the problem because the engine is going well and sounds nice i "neutral" mode and Can rev up in 5k rpm. But Mabye it Will be worth a try offcourse. Hehe in Sweden you Will not find any Cable kits under 150$ the parts to american made engine is ridiculously expensive. Just the knock sensor is a 120$ investment

 

[scoflaw]

Revving in neutral means nothing. Buy some MSD wire from Summit Racing and make your own.
So your saying you have 17 year old wires ?
What's your fuel pressure doing at WOT?

 

[Memike]

Revving in neutral means nothing. Buy some MSD wire from Summit Racing and make your own.
So your saying you have 17 year old wires ?
What's your fuel pressure doing at WOT?

All the ignition cables are changed for 3-4 years ago to org Mercruiser.

I dont know yet, next week i Will go up to the west coast and see. (2,5h drive) frome Here) that also a issue

 

[Jeff Delbuono]

I had the same problem this year. 1998 290 sundancer with twin 5.0 efi. Ended up being a weak fuel pump on one of the motors dragging the other down. Trust me like you I changed every sensor or module there was. Its a fuel starvation issue. Start there

 

[Memike]

I had the same problem this year. 1998 290 sundancer with twin 5.0 efi. Ended up being a weak fuel pump on one of the motors dragging the other down. Trust me like you I changed every sensor or module there was. Its a fuel starvation issue. Start there

Ok, so the symptoms were the same?
I guess theres no fault code if i try to read the engine because i Have no failure alarm noising.

How did you go about finding out that it was the fuel pump?

/M

 

[Jeff Delbuono]

Talked to a merc master tech. Motor needs fuel, air, electric. No shreader valve to check psi on fuel. Cool fuel 2 system. While changing pump i blew all fuel lines out. Some crap came out of water seperator housing. I would concentrate on fuel system.

1) Boat ran and sounded great at dock and up to 3000 rpm
2) hit rev limit in neutral all the way to 5000 rpm
3) no codesn or alarms ever
4) boat would jump to 2500 rpm and never get over 3200 rpm and just fall flat.
I spend 3 months, $1800 in parts and $1200 in different mechanic advise. Find a merc master tech. Kiss the ring and ask him only. They are tough to find but when ya get one hold him tight and take his advise

 

[Memike]

Talked to a merc master tech. Motor needs fuel, air, electric. No shreader valve to check psi on fuel. Cool fuel 2 system. While changing pump i blew all fuel lines out. Some crap came out of water seperator housing. I would concentrate on fuel system.

1) Boat ran and sounded great at dock and up to 3000 rpm
2) hit rev limit in neutral all the way to 5000 rpm
3) no codesn or alarms ever
4) boat would jump to 2500 rpm and never get over 3200 rpm and just fall flat.
I spend 3 months, $1800 in parts and $1200 in different mechanic advise. Find a merc master tech. Kiss the ring and ask him only. They are tough to find but when ya get one hold him tight and take his advise

Aha, i think it will be totally impossible to find one in Sweden. Now i have order a new knock sensor, map sensor, rotor and ignition cap and a fuel pump. I´m going to comp test all cyl and the pressure of the fuel aswell. But if i can solve it with this it will be worth it.

What was the failure with your engine?

/M

 

[Jeff Delbuono]

You have the cool fuel 2. This has a fuel pump and a fuel regulator on top of cooler. The fuel pump has a screen on the front and the fuel regulator has a small hat style screen in it. My issue was that the pump was weak. My screen was dirty and i just changed the fuel regulator just cause i was there. While i had the fuel lines off i blew in to all of them. Disconect fuel/water seperator. Watch and see if crap blows out

 

[Jeff Delbuono]

 

[Memike]

View attachment 73842 View attachment 73843 View attachment 73844

Are you sure its ok to set that adapter after the high pressure pump?

 

[Jeff Delbuono]

I did not use it. That is what other people told me i would need to check fuel pressure. My 5.0 did not come with a shreader valve

 

[Espos4]

Are you sure its ok to set that adapter after the high pressure pump?

That adapter is needed for TBI applications that do not have a Schrader valve for hooking up a fuel pressure gauge.

If you have an MPI motor or anything with a schrader valve in the fuel line, than the adapter isn’t needed.