Smarty pants, I really could use your help! 350 Mag trouble SOLVED?? MAJOR UPDATE

212rowboat

you're running out of fuel on that engine... most likely it's due to bad pump or obstructed filter... 

looking at the vacuum signals, though, I'm still not convinced there isn't a maladjustment in your valvetrain, especially on intake valves.  are your rocker ratio's matching on both engines?  

Wildboating

Pump shows 40psi steady at anything in advance of neutral.  Neutral shows 45.   The filter is new, I'm going to replace the water / fuel separator.    What makes you think i am running out of fuel?  By the way new injectors today.  May have made a minute difference, i noticed i am able to pull throttles back to even at 3500 and stay at same speed.  But that difference between 50% and 3500 rpm still do nothing.

212rowboat

I should just offer an observation instead of offering absolute such as "you're running out of fuel" when I should say "you're tapped out and operating at max production for any given rpm when the signal is zilch".  

an unregulated air supply, aka a vacuum leak, will cause this... but also, lack of fuel will only allow forcible downstroke, which is what creates vacuum...  I don't know exactly how to communicate this....

...but.... I can indicate that it results in a lean running condition... so... pull a spark plug... if it is white or light in color (the electrode), it is running lean and hot, and speaks to lack of fuel.  there ain't no way around that, either... it is hardcore evidence.  

Black_Diamond

Wonder if he tuliped the valves?

Wildboating

@212rowboat. Thanks for the explanation. Plugs are coming out next. 
Bd, valves were tuliped last year, we rebuilt the heads at the beginning of the season.   I have limited hours since then so all should be well but I guess another compression check is in order. 

Black_Diamond

Something to consider, the fuel lines on my 342 were pulled tight thru the firewall hole. Really tight. I replaced my lines from the tank to the firewall mounted fuel filter and put in a big loop to make that corner. This was part of my fighting your same problem. If that line is kinked, big flow restriction. 

Liberty44140

Does this engine have two fuel filters per engine like my 350 MPI horizons do? Are both fuel filters new and clean? Easy to only replace the main and not the white disc. 

Black_Diamond

Should only be the in-line filter on the firewall and the fuel/water seperator for that year/motor. 

Black_Diamond

Back to the tuliped valves, my understanding this is from over propping/ lugging the engine. Did you solve the initial cause for that?

Michael T

Questions: ***Your engine is fully warmed-up (normal operating temperature) before taking vacuum readings? What are you using for a vacuum port - for example - using a pcv line will cause the engine to run richer? If you have a ported vacuum above the throttle plate you can eliminate the throttle body to carb gasket. Gaskets?......Gasket under arrestor? Carb gaskets? Intake manifold gaskets? Soap test? Again....you have checked both throttle linkages/cables for exactly the same length, travel and adjustment and there are no hang-ups?

Wildboating

@Black_Diamond   The tuliped valves were from lugging the motor imagine.  I was told and it was suggested last year here on the forum that the problem was because my 24p props.  I repropped with 22p 4 x 4's from hill marine over the winter however that did not change the motor making power over 50% throttle.  The day I launched the boat that same problem motor started making a knocking sound.  So save our summer, and seemingly fix the motor issue we bought a new long block.  Sadly, even with new engine the problem is still there.

Wildboating

@Michael T  The engines are fully warmed up as we have about a 30 minute river cruise out to the open water due to wake zones and bridges.  I used the vacuum port directly off the top of the intake manifold, behind the throttle body that goes to the pcv valve in the valve cover.   Definitely not a mechanical throttle issue, the ECM confirms that we are going from 0 to 100% throttle through the entire range.

I am going down today to try the ether leak check and also put a loose fuel cell in the boat to eliminate the boat fuel system.  I have 45psi at idle and 40psi under load.  So i think it is safe to eliminate the fuel pump.  Fuel filter is new, i will replace the fuel water separator today too.

Wildboating

What is the likelihood that i have something wrong with my outdrive however it runs smooth and makes no noises?  My mechanic buddy wants to swap the drives to eliminate that as a possibility but throwing another 200 away to lift the boat plus a few bottle of crown for him sucks..  I am literally bleeding out on this boat.. LOL  If it was just this issue it would be one thing, however it is always something else.  Before its over, this boat will be completely all new.   I have replaced or upgraded everything it seems like.

Black_Diamond

If something was wrong with the outdrive/powertrain that engine would be lugging.  There is really nothing in that outdrive to cause that kind of load, even if it was destroying itself the engine has more than enough power to push thru it. Bad bearings/chewed up gears..it would quit spinning the props before seizing up.

Can you get the engine up to ~5,000 rpm in neutral (unloaded)? 

Have you tried having the 'bad' engine pulling fuel from the opposite tank only? (close off the other tank valve)

I agree with 212, it really sounds like a lean running issue: vacuum leak or lack of fuel. Checking the spark plus will say a lot and it is cheap.  Plus they don't lie!

  

212rowboat

i'm a little reckless I'll be the first to admit- but to kill two birds with one stone:  buy a few feet of fuel injection hose, and cross them over..... intercept the rail feed and feed the opposite engine with it... see if the issue follows to the other engine...  

if this was a car engine, this would be a lot easier as there are o2 sensors sniffing exhaust at all times... it's registered in lambda and expressed in % of trim, short term or long term... the issue with your engine?  it DEMANDS the 'mechanics' of the fuel delivery be accurate, and takes it as gospel that the pressure is constant in the strict parameters prescibed to run the engine.  it has no o2 sensor to reconcile that the MAP/MAF, IAT, temperature, and TPS are doing their jobs correctly... it's a flaw in their design, so far as I'm concerned- I get why they don't (tapping and heat), but- there could be a way... there should be a way... 

you can't even stick a wideband o2 sensor in the exhaust to sniff... because water is mixed at the head of the riser and spent toward the Y through the bellows... that makes it impossible... 

because you can't do this, you gotta do the old fashioned thing and read/interpret spark plugs... and use a vacuum gauge... 

you indicated you installed a long block... turn key? or, long block?  a long block to me is a block, rotational assembly, timing chain and front cover, water pump and heads... it lacks intake manifold and fuel systems, exhaust manifolds and risers... some lack oil pans, but most have those.. you use the rest of what you had to make it work... it stands to great reason your issue followed because you reintroduced the faulty item... that faulty item could have tuliped your valves due to lugging caused by heat caused by lean caused by something as simple as a blocked vent on your fuel supply.... 

my contention remains... vacuum leak or fuel limitation... 

Black_Diamond

Good idea on the fuel line swapping! 

Wildboating

The saga continues....   

Today swapped the fuel regulators - didn't help
Ran problem engine out of a 5 gallon fuel can- didn't help
Sprayed every gasket, vacuum line etc with ether- didn't help or find a raise in rpm

Tomorrow calling engine provider to verify the same cam profile is in new engine to see if that explains the vacuum difference. 

**. Driving with hatch open today discovered problem motor sounds stressed, like it is under extreme load where good motor spins freely.   My mechanic really thinks either boat has wrong gear ratio / different ones on each engine.   Supposedly boat had new lower drives on both engines before buying it.  Going to pull boat and swap drives.  This is driving me insane!!!!!

Wildboating

Engine spins freely and without lugging in neutral to 4000 and I'm sure higher.  I just don't feel the need to push it there, you can hear it has no problem revving up

Wildboating

New fuel/water separator.  

Wildboating

So based on bd's comment that drive can't be binding enough to cause this, I guess the boat has some whack gear ratio on that side?  Really, what else could it be.  Hearing the engines today was eye opening.  Felt like it was unsafe to drive with hatch open but didn't have choice with external fuel tank. 

NavyCTRC

I know the feeling, break out another thousand (B.O.A.T.) is hard to do when you only have $16 bucks left over from the last 10 times....

Wildboating

Also, in gear with throttles all the way back good motor idles at 800 rpm, bad motor at 500

212rowboat

the drive is stamped, and is legible if you're patient enough.  I think it's starboard side, near top fin/flare.  unless someone opened the case and swapped R&P's, that should answer your question.....  the other way is to pop off the top cover and count teeth.  

Black_Diamond

I suspect he'll have to pull the drive to get the ratio. The B-III has the s/n and ratio on a sticker (yes) on the upper unit. Rarely stays on. Pull the drive and count the input shaft rotations to prop rotations. 

If not a ratio issue, Be interesting if you got the correct long block for a 350MAG MPI. 

Wildboating

@Black_Diamond. Issue was prior to replacing long block 

Wildboating

Sticker is gone from drives.  Going to half to pull boat out, yank and count. Sucks,  dropping hundreds like no tomorrow.   Wife is questioning why I don't spend on her like I do my mistress.  Seriously, love Rinkers just sucks I mistakenly bought someone's problems.  Guess getting a boat 10k under value wasn't such a great deal.  But dam if she won't be perfect soon.  New everything. 

Black_Diamond

So, pull the drive.  IF the original u-joint shaft is there, it has a letter code on it for the drive ratio, assuming no one changed the internals.

                                                         
Letter              Gear Ratio          
B                     2.00:1               
G (gas engine)  1.81:1              
F                      1.50:1                 
K                      2.20:1                 
D (Diesel)         1.81:1                  
C                     1.65:1                   

At least when you count the input Vs output turns you know what to look for.  All of the gear reduction is done is the upper part of the drive I believe, not the lower.  Thus why you could swap a B-III lower onto a B-II upper. I am willing to be corrected on this  lol

Wildboating

I was told the lowers have the gears. Google, here I come

212rowboat

as i understood it, they could BOTH have gear reduction..... or the bottom could be 1:1 and be the only difference between 2.2 and a 1.8, or a 2.0 and a 1.5.... 

the internet.... everything on it is true, so sayeth abe lincoln which was validated by napoleon.  

Black_Diamond

The upper has the 90 degree gear set.  The lower has gears too, again to make the 90 degree turn AND then spin the inner/outer prop shafts in opposite directions (B-III).  Could have another gear reduction at the lower 90 degree turn.  Not a lot of room to fuss with it in there (lower), busy gear train!

Good one on the 'truth is on the internet!'  lol  Somewhere....