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

212rowboat

i wouldn't pull the drives before i'd exhausted other issues... just me, though, I guess... 

i'd adjust the valves- on a new head that wasn't adjusted after camshaft break-in, there is a great chance their out of adjustment... it's a ten minute job, and would manifest as a vacuum leak- the RPM's charging the lifters and keeping the valves from sealing, creating an absolute dead spot after they're charged.. I'd do the fuel cross over and see if the issue follows after the valve adjustment... i'd read the plugs... i'd take my dizzy off and search for evidence of spraying, and would look very closely at timing- if the timing isn't advancing (your base timing is too low) it will run, but it won't be generating any power past a certain spot... there are a ton of little things like this that can be done in an hour or two prior to breaking out access to the account... 

but if you must...................... before i pulled the drive, i'd go over to a prop speed calculator such as HERE and plug in my speed (gps), my RPM (shop gauge), estimated prop slip (use known good engine to reverse calculate this) and see which it came close to matcing.. they are far enough apart (the available ratio's) that this ought to work...  

Wildboating

@212rowboat. Thanks for all your help as well, you are very knowledgeable and your help is greatly appreciated. . I know it is a long thread but most if not all of your suggestions have been exhausted.  This problem existed prior to replacing the engine. The exact same issue. 

frodo13056

Same cap / rotor / distributer / coil on the problem engine? 

Wildboating

Yes, but all are 2 years old. 1 year old when I bought boat and problem started

Wildboating

/ present. Issue from day 1 of buying boat. 

Black_Diamond

I'd be exhausting/replacing all the easy/obvious stuff: cap, rotor, wires, plugs, fuel and fuel water filters. Check all your connections. Make sure the screw connection of the cap to Distrubutor is not broke (trust me). Use the Merc parts, not substitutes. Check the risers for restrictions. Even snake the exhaust Y-tube for blockage. 

You can get more corrosion in the dist cap than you think even in a year, worse if the cap has AL posts. 

It would be a pretty bad mistake to have the wrong drive ratio on one side, that's for sure. Major f-up. It would have to be way off to have the effect you are seeing I believe. 

Frustrating problem, been exactly there. It is fixable!  Maybe it's just me, but I think this problem is more simple than you think. I was a hair from replacing/pro-cleaning injectors myself. In the end the PCV and that PMAP/TMAP sensor was the true problem (I replaced on both engines, because why not). I know I fixed/prevented other problems along the way. lol. This was AFTER changing from 24P to 22P props too. My GPH match now too, the port engine (problem child) would always burn 4-8 gph more than starboard. Throttles match, or as well as they can. No more rpm drop as I throttle up too. 

Edited a lot, better than another post I figured. 

raybo3

How could it be the drives when Wildboating said he has the problem even in neutral? This thread is 4 pages long so maybe this has been covered already but is it possible that you have a restriction on the exhaust and that is why it is struggling??????? 

aero3113

Is there anyway the throttle lever can be indexed wrong on the throttle assembly?

212rowboat

here is the thing..... plain and simple..... and it's verified with the pics and the video clips:  

he runs out of power.  he can generate the RPM's, but he can't produce power.  

there are three things that i would zero in on- and only because of the conversation in the thread...

1. find out what kind of distributor is/was in the long block.... set the base timing at the OE specs, and lean over and do the same thing to the good engine.  put a new cap on it along with rotor button- it could simply be spraying spark which wouldn't be evident until it hits the point in the rpm range it loses it's direction.  also, related- and this is going to hurt:  pull the front cover and make sure the crank and cam are properly aligned... one tooth ONE TOOTH off, and...... toss valve, fuel sync, and ignition timing out the window... 

2. adjust the valves.  pull a single valve cover, grab your 5/8 socket... place a towel loosely over valves you're not adjusting, fire engine and loosen rockers until you hear a decided taptaptap... then reverse course tightening them until there is only a slightly audible tap, and then 1/8th turn beyond.... move to the next valve.  do them all... here is why:  if the valve train is too tight, it will be silent- you DON'T want absolutely silent... you want there to be just the slightest tension on the rocker tip to push rod when pressure is relieved on that spring... if there is too much, and once the engine gets above 2500~3000rpm the hydraulic lifter overcharges and becomes dang near solid- and will not allow the valve to seat- which cuts drastically into compression read:power... the engine will appear 'dead' at this point... it will cut into vacuum signal.  it will be spinning, yes, but it won't be producing much power.  

3. cross over the fuel supply by intercepting the line going to the RAIL... see if the issue follows... 

Black_Diamond

No timing to adjust on that engine, just need to have the dist installed so the rotor is at the correct position when #1 is at TDC. The sensor on the engine takes over. Since he had the problem with the old engine, it must be something carried over from the old one. 

Wildboating

@raybo3 the problem does not exist in neutral.  The engine sounds free and spins easily.  

Wildboating

I appreciate the suggestions but this issue was the exact same with previous motor, installed new long block this year and problem carried over with the exact same conditions.   This issue is not inside this motor.  With that said, I will make the adjustments as @212rowboat has suggested to ensure motors are running at the optimum performance.  

Wildboating

If it is not the drive, what else could be binding up the motor.  You can hear it grunt from low rpm up to its max speed.  I was shocked to drive with hatch open and hear it.  When in neutral both engines show same rpm, in gear problem motor is just over 500 rpm where good engine idles at 800.  It's like as soon as I shift into forward the motor goes under heavy load.  

raybo3

Wildboating said:

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

Sorry I thought you meant in neutral.... Maybe swap the drives to see if the problem follows the drive unit............ I know that would be a PITA but at least you would know what if it was a drive problem or an engine problem........

Black_Diamond

Do you get a lot of vibration with that engine in gear?  At idle, even over propped or wrong ratio should not do much of anything. Is your engine/drive alignment good?  Motor mounts good and tight?  Misalignment can put a lot of drag on the motor and if it is moving when put in gear it will get worse. Same rpm drop in fwd and rev?

Hard to fathom the drive adds that much drag, even if it is failing. I had one almost destroyed and it still functioned.  Almost sounds like the engine can't respond to a load. I'm really running out of reasonable ideas here. lol

Let us know how the drive feels to rotate even still on the boat. And the ratios. Good luck. 

dalek

Just a thought.
Is it possible that you could start both engines, put both in gear, then turn engines off while tied up? You could then put a torque wrench or similar on the crank nut and measure the force needed to turn each motor.

212rowboat

did you reintroduce all the drive belt accessories?

NavyCTRC

I think just the block and internals were replaced, same heads, intake and accessories.  As hard as it is, if swapping the drives to rule that out and checking tension on the valve train doesn't fix the issue, I think it might be time for a valve job.  Maybe the valves are floating at higher RPMs, hence no power.

reneechris14

Motor turns 2.2 out put shafts 1 full rotations 

Weber

Wow, you are spending a lot of cash on this problem.

Have you had an actual mechanic look at it?  Might help to have someone that could guarantee their skill and work.

I had the same boat, and had a similar issue but with the port motor.  It was fuel related and was starving for fuel.  No codes or alarms, just lack of rpm's on the top end.  Took a while to figure it out, but was a simple fixed once I figured it out.

reneechris14

Wrong outdrive sounds like a good reason for over Rev when you put the set of props (20 pitch)

212rowboat

pull a plug on the sick engine and read the electrode to see if she's lean... 

Black_Diamond

Any update?  Gone quiet. 

Wildboating

Been submitted into a insanity hospital... boat drove me nuts!    

I travel for work, sadly i wont be able to swap drives until late in the week.  I needed to go make some more cash to throw at my ride.

Wildboating

@Black_Diamond  I don't notice a lot of vibration but like i said, the motor really sounds like it is lugging.

@dalek  That sounds like a great idea, i will run that by my mechanic buddy tomorrow.


@212rowboat  All accessories and drive belts are intact and remain the same between the two motors.


@reneechris14  My mechanic buddy said the same thing but my issue is that was with analog gauges and 20p.  I really have no idea how fast that motor spun but to not be able to get over the 3500 rpm range with 22p as I wasn't able to do with the 24p makes me think that couldn't be.


@Weber  I checked fuel pressure on the rail and verified it says over 40psi at any rpm or load.  Swapped fuel regulators and noticed no difference either.


All,  I put a 5 gallon fuel can on board and disconnected the fuel line from the fuel filter.  The boat reacted exactly the same.  The problem as been eliminated from a fuel issue.  With this test, new fuel / water separator, fuel injectors, regulator and verified pump i feel we can safely remove this from the options.  

Michael T

....and the cables are fine all the way back?.....they are properly adjusted?.....there are no bends, kinks, hang-ups?....you have taken the cover off the helm throttle housing to check them: no loose parts, hang-ups, previous owner modifications and checked the travel and cable adjustment right at the throttles.

raybo3

I still think you should switch the drives and see if the problem follows the drive. Seems at this point thats all it could be............ Good luck and keep us posted.

Handymans342

Arent the drives counter rotating? 

Dream_Inn

Handy, drives are all the same.  Props are what is different (like our B-2 drives have L/R props)

Black_Diamond

That drive ratio would have to be way off to cause that problem. It should have got better dropping from 24P to 22P too, and it didn't he said.  I'm still betting on that TMAP/PMAP sensor.  Replace it with a NEW one. Virtually the same issue I had.