WOT 5.7 vortec v8 in delta 25

EdBence · 21-11-2015, 03:21 PM

Hi, I have a sonny levi delta 25, and am struggling to achieve wot the engine is new, just run in I have tried various carb configurations including 2 quadrajets and a brand new edlebrock which is supposedly ready setup for the engine, 2 fuel pumps etc running delco est ignition. was running a 17 prop and got 33 knots at 4000 rpm where it starts to bog and fluctuate, apply more power and its just louder IE secondaries opening more. I then installed a 19 prop just to try it because I had it I know its the wrong way around ! and it still does the same rpm and symptoms but goes to 38 knots. it will also not rev above 4000 in neutral I believe the issue to be ignition related, I have tried adjusting the advance etc the only things I can think of is although I believe there is a decent 12v supply to the coil maybe not, or possibly that because my shift interrupt is closed in operation and open to interrupt I have had to wire it through a relay so it just cuts supply to the coil to interrupt therefore could the ecm be thinking the engine is at a different rpm to what it actually is ... the other thought I had was the old merc flame arrestor is clean but possibly restrictive. any thoughts or suggestions please, not that I particularly want to go faster but its nice to know its there ! Thanks !

NickGT40 · 21-11-2015, 04:37 PM

Hi just a thought maybe you are running out of fuel at higher rpm due to pick up pipe in petrol tank or diameter of fuel hose,air vent in tank blocked fuel pump etc.,try running engine on a driffrent fuel supply good luck nick

EdBence · 21-11-2015, 05:30 PM

thanks nick for your suggestion, I'm not sure though because if that was the case wouldn't it give a short burst before the starvation ? + if I put the fuel pipe into a tank and turn on the pump the pressure is massive I will give it a go though !

Drag Racer · 21-11-2015, 10:07 PM

New Crate Engine or Rebuilt old unit ?

EdBence · 22-11-2015, 01:30 PM

hi, it's a new crate engine, the old engine was a non vortec and had the same symptoms I just thought because of the age it was as much as it would do... so fitted a new one that and the old one was very corroded. other info the exhausts are pretty much straight through except 2 very short inline mufflers, I fitted the edlebrock carb with the new engine (650cfm) so I think the carb can be ruled out as the old engine did it with the Rochester quadrajet. The ignition is delco est, I'm wondering should the paint be stripped off the coil mounting for it to get a better earth? the 12v supply is via a relay from the 12v ignition switch & shift interrupt so when the relay is activated the coil gets 12v straight from the battery switch, any ideas appreciated I'm flummoxed !

Drag Racer · 22-11-2015, 04:48 PM

Did you just drop in the distributor and set timing engine at idle with timing light ?
If you did then the timing may well be way off across the range !. Your set up has an electronic advance / retard unit, which sets the advance / retard required from various engine / driver demands.
You will have two plugs at the distributor. One should have only two wires, the other three ( possible four ). Unplug the bigger plug. Now when you bought the boat you should have got a bridge out plug ( bet it's gone ), you could be lucky and it has been cable tied to the engine loom, just sitting there looking pretty. Same plug as you have just unplugged but it has a loop wire and the other is just a tail. plug this into the distributor, start up the engine ( warmed prior ) and connect the tail to a good 12V supply. This locks out the Electronic Advance / Retard Unit.
Set your distributor with timing light. Now this is the good bit as the base setting could be anywhere between 0 to 8 degrees BTDC, you need to get the initial advance setting from the engine supplier or use the Mercruiser setting for the old engine. Lock down the distributor.You may well have to adjust idle speed while doing this.
Shut her down. Unplug the bridge out plug and plug back in the original plug and the Electronic unit will now be back in command. Fire her up and let her idle for a few minutes, just to let the self seeking parameters of the Electronic unit do their job. Take her straight out and see what happens.
If the bridge out plug is not present, you can buy made up ones for about $8 just google. A good Auto Plug supply shop should have the plug type ( 2 types Round terminal or Square terminal ) and make up your own. You could go straight onto the socket pins as well. Let me know how many wires the plug will "take" so I can tell you which terminals need to be bridged and supplied.

EdBence · 22-11-2015, 05:06 PM

Thanks Drag racer, I built the boat up from an empty shell, so the loom is home made, but good, I installed the distributor with the jumper wire as you describe, it is set at 10 btdc at 800 RPM and does advance when revved although I'm not sure how far as there are no further marks on the bottom pulley and I only have a basic timing strobe, according to the distributors instructions, the four pin plug you speak of just connects to the shift interrupt during normal operation although because of my interrupt switch being circuit closed for operation and open for interrupt it is wired through a relay to the 12v supply (cutting the ignition on shift by killing the 12v supply) so that four pin plug in my application is unused apart from initial timing ?? or am I completely wrong with this setup thanks Ed

Drag Racer · 22-11-2015, 09:00 PM

10 BTDC is heavy. The Module will give you 20-22 advance, so you are now running all out 30-32 BTDC @ 2800/3000. Depends on the 5.7 engine you have, the base advance needs to be anywhere 0-8 BTDC. Remember if you fuel from a pontoon, that fuel is more than likely been hanging around for a long time so it will not like lots of compression and advance. Set her at 4 BTDC and give her a run out. The shift switch is only there to cut the motor as you go into forward or reverse. Take it out of the equation
Set the idle at 6/700 this will help any sharp shift engagement.
Ignition coils are designed to see 12v, any higher and they burnout. Split all the plug leads with separators, best still get a set of MSD 8.5mm leads and separate them.
Don't forget port odd & starboard even, make sure they are in correct firing order. Cost us Pheonix NHRA final, had to go to Tucson to get the job done just for wrong lead,wrong plug.

EdBence · 22-11-2015, 09:17 PM

thanks for that,I think your right I am thinking along the lines of shift interrupt, because the way I'm doing it (cutting power to the ignition via source) could I be fooling the module into thinking its at start up rpm (I have been told it retards to start?) I take fuel down in jerry cans and have tried super etc with no difference. I have lead seperators and the leads are 8.0mm so maybe I should go bigger but they came new with the kit, they are on the right way around. it drives almost as if there is a limiter at 4000, however when it bogs if you apply additional load like make a heavy turn or trim down it sweetens up but still no further than 4000 thank you for your continued help