Marvel Mystery oil in a 2004 5.0 engine

[Dp59]

Has anyone used Marvel Mystery Oil in the 5.0 engine?
If so did you see a deference in engine performance when added to the gas tank?

 

[lprizman]

No.
Is this a new to you engine?
Why are you considering a wish and a prayer in a bottle?

 

[Dp59]

No.
Is this a new to you engine?
Why are you considering a wish and a prayer in a bottle?

Yes it is a new to me engine and it seems a bit sluggish when putting the hammer down.

 

[racerone]

That oil is on the shelf because folks buy it.----Oil is not well understood.

 

[paulswagelock]

It has a purpose, but what you are hoping for is not it.

 

[lprizman]

Well....I've used it prior to an oil change only...about 15 minutes prior at idle only.

A compression check of each cylinder would be more telling.

Sluggish when launching could be many things...hub...prop... excess water in the bilge...fat people...bad fuel...cligged fuel filter...bad primer ball.... trailer still attached to boat..need trim tabs or foil....proper weight distribution ect....I've seen Evey one of these in my time...

What steps have you taken so far?

 

[LundAngler1650]

Call me crazy, but I don't like additives be them in my gas, or oil. Run a quality oil, run quality gas, and let that be enough, is how I do it.

 

[LundAngler1650]

Well....I've used it prior to an oil change only...about 15 minutes prior at idle only.

A compression check of each cylinder would be more telling.

Sluggish when launching could be many things...hub...prop... excess water in the bilge...fat people...shitty fuel...cligged fuel filter...bad primer ball.... trailer still attached to boat..need trim tabs or foil....proper weight distribution ect....I've seen Evey one of these in my time...

What steps have you taken so far?

This actually made me laugh. Well written

My boat is drastically underpowered, I jokingly told my gf I need to trade her in on a smaller one. She knew that I was joking, and laughed, then promptly reminded me that my 181 lbs is substantially more than her 117 lbs. She then jokingly suggested we sell the dogs, which neither of us would never actually do, but they are heavy.

 

[lprizman]

One step at a time.... process of elimination....you'll get it dialed in!!

 

[Bt Doctur]

it no mecanic in a bottle but my f250 went over 400K using it in both gas and oil

 

[Dp59]

Well....I've used it prior to an oil change only...about 15 minutes prior at idle only.

A compression check of each cylinder would be more telling.

Sluggish when launching could be many things...hub...prop... excess water in the bilge...fat people...shitty fuel...cligged fuel filter...bad primer ball.... trailer still attached to boat..need trim tabs or foil....proper weight distribution ect....I've seen Evey one of these in my time...

What steps have you taken so far

 

[Dp59]

First new fuel filter/water separator, no help. Compression test 180 on all cylinders. Check fuel, no water in it. New dist. cap and wires. New plugs
New fuel pressure reg. as old one was maxed out at 36 lbs. no codes show when reading with Tech Mate software. Flushed injectors with K100 with fresh fuel from can. Thought i would try some of this before we go new ecm route.

 

[Dp59]

First new fuel filter/water separator, no help. Compression test 180 on all cylinders. Check fuel, no water in it. New dist. cap and wires. New plugs
New fuel pressure reg. as old one was maxed out at 36 lbs. no codes show when reading with Tech Mate software. Flushed injectors with K100 with fresh fuel from can. Thought i would try some of this before we go new ecm route.

The problem is that the motor will sputter and die after a few minutes at any speed .Will run all day on the muffs but when going out under load this happens. Let it sit for a few minutes it will start again and away we go for a few minutes it stalls again.

 

[Scott06]

Ok when it stalls and will not restart have someone pump the throttle forward while you look down the bores of the carb if yiu see two solid streams of gas you likely have fuel in the carb. check for spark take the coil wire off the distributor and ground it see if you get a nice blue spark that will jump a 3/8” gap.

what do your spark plugs look like ? Are they black and sooty or dry and white looking? Black is too rich like needle and seat isnt working and flooding the carb or choke is sticking,dry and white is lean lack of gas

 

[Dp59]

Ok when it stalls and will not restart have someone pump the throttle forward while you look down the bores of the carb if yiu see two solid streams of gas you likely have fuel in the carb. check for spark take the coil wire off the distributor and ground it see if you get a nice blue spark that will jump a 3/8” gap.

what do your spark plugs look like ? Are they black and sooty or dry and white looking? Black is too rich like needle and seat isnt working and flooding the carb or choke is sticking,dry and white is lean lack of gas

It's a MPI engine with brand new mercruiser platinum plugs. No carb.

 

[RaceCarRich]

Did you change all fuel filters? Not sure if you have cool fuel module in addition to water separator. Cool Fuel takes 2 filters.

 

[GA_Boater]

Check that the tank vent hose is clear. Try cracking the filler cap open and see what happens

 

[Scott06]

It's a MPI engine with brand new mercruiser platinum plugs. No carb.

Ok what did the old plugs look like? What rpm is it when it dies?

 

[Dp59]

Ok what did the old plugs look like? What rpm is it when it dies?

Old plugs looked fine but trying to narrow it down as much as possible. It does not matter what rpm's it running at when under load. Still stalls out.

 

[Dp59]

Check that the tank vent hose is clear. Try cracking the filler cap open and see what happens

Fuel vent / overflow is open.