1994 omc 5.0 ho 2 to 4 bbl swap

[jimmbo]

Check to see if the timing is correct and that the advance mechanism if working. Also check to make sure the carb is opening fully, and that the choke is fully open. The edelbrock should help even with the 2bbl as the small ford does have a choked up induction system. You might want to restrict the heat crossover passage a bit, as the aluminium will transfer more heat to the runners than the cast iron manifold did

 

[jj50cal]

i am going to let someone else look at the timing just to be safe, and i will definatly look to see if the venturies are opening up all the way, i know the choke is, that was the very first thing i did. and again,and again. question: will it hurt to change the distributor to a standard ford type , such as a msd, or accel electronic distributor?

 

[jimmbo]

If it has the correct advance curve, and provided it meets USCG requirements. Vacuum advance as on a standard distributor is not used on marine engines

 

[jj50cal]

ok thanks, just curious. i' wanting to get the utmost power and torq, as humanly possible. i have even already ordered a new 4 blade prop from iboats that should be getting here any moment. i'm really not use to small block ford or chevy engines that won't burn up the track when i stomp on the gas. the engine in my 1968 chevelle started its life as a heartbeat in a 1963 split window corvette with a six pack on top. then reborn with a larger cam and holley 750 cfm dbl pump, that did double duty from the 68 chevelle mon-fri, to a '78 jet boat on sat-sun. no problems going back and forth there, so i thot it would be the same diff, on a prop boat, boy was i wrong....:grumpy:

 

[jj50cal]

11:30pm update, got the new 4bbl to 2bbl adapter installed, now has a 21/2 inch drop, over the stock iron intake, runnin a little rich, but gonna have someone check my float level besides me, and make sure the timing is correct again. not gonna put the new 4 blade prop on until i'm sure this problem is clear first.

 

[jimmbo]

2 1/2 inch drop? Do you mean the carb is sitting 2 1/2 inches higher than when it was on the stock intake? Float is easy. Take the fuel bowl off, remove any baffle around the needle and seat. Invert the bowl and adjust the float so what is now the bottom of the float is parallel to the float bowl

 

[jj50cal]

yes it is now sitting 21/2 inches above the stock manifold. i love this picture it's a great visual. thank you,

 

[jj50cal]

ok just got back from test run, a little better, but still just a parade boat (slow) got it to do 3200 rpms and about 30 mile per hour with 2 passengers, much better take-off, but no top end. still gotta pull the plugs, my son was adamant about trying it out with the triple platinum gapped at .055, can anyone tell me what the omc or the four winns book says the gap should be on this motor? i have found info that says .035, and also .045, also, has anyone had experience with the D.U.I. marine distributors? someone i met at the river today said that is what he put on his jet boat, and it improved his performance.

 

[jj50cal]

question please.... would it be possible for an exhaust flapper or is there an exhaust flapper on my boat, if there is could it be lodged someplace? or have come loose? just curious, i found a forum where someone with a 1993 four winns with a 5.0 was having the same problem as me, and he claims his exhaust flapper were missing, and had become lodged in his out drive. if mine has this how would i check for this ?

 

[jj50cal]

ok i was looking at another forum (ifour wins), and someone there was having the exact same problem. turns out it was'nt the carb, nor was it the timing, not even the spark plugs.... turned out to be an exhaust problem, we crawled under the stern drive, and lord and behold there was a flapper valve stuck right above the anode on the transom, pulled it out, and then opened up the exhaust tubes, and elbows, pulled out both of the hinges, and looked for the second flapper, but there is not one to be found, cranked up the motor, and it sounds great, it has never sounded this good, ever.... putting it in the water tomorrow to see what happens.. wish me luck,,,,, thanks folks, for all of your help....... jj

 

[jimmbo]

I guess if the exhaust can't get out, then fresh air isn't going to get in. Hopefully that is you problem. Just a Warning, without the flappers, your engine may be prone to having water come rushing back thru the exhaust when slowing down or are stopped and waves are slopping around the transom, and entering the engine thru an open exhaust valve. It may then hydrolock and will not be able to rotate. If you suddenly find yourself with a 'seized' engine, remove the spark plugs and then try cranking it.

 

[Lou C]

Flappers are in the upper end of the Y pipe after you remove the exhaust risers. If they melted from a past over heat they will be in the bottom of the Y and you will have to pull the drive to get them out.
Check the drive ratio, if it's off that could be a factor in not reaching max rpm.
I would get rid of the plat plugs old school engines run better on conventional plugs. Also check your total timing advance at the specified RPM.
Old school ignition not designed for plat plugs.

 

[jj50cal]

Ok at the lake now, engine runs a little bit better. I couldn't resist putting the new 4 blade prop on first if the engine gets right it'll. Be funner as h e dbl hockey sticks, I got it up to 4000rpms with new prop but only 30 mph. Put the old prop back on and got the same results as before. 900 lbs of passengers and was able to get 20 mph, at 3000 rpms gonna let engine cool down and pull the platinum plugs and try it again tomorrow.

 

[jj50cal]

Oh yeah, I only found one flapper found both rods that hold them in place. But the one I found was above the anode on the transom. Any idea where the other might be

 

[jimmbo]

If it is still in there, it may have wedged itself in many spots. You don't have one, or know someone with a fibre optic camera? Snaking one of those back up the exhaust system beats taking all apart

 

[jj50cal]

i may know someone who does have one of those, he is a fireman, plumber friend, think i will give him a call tomorrow, i had the lower unit off once, 12 hours later i took it to someone else to put it back, the drive shaft kept falling just as i would get it lined up. don't wanna go thru that again.