7.4 Mag MPI Issues out of hole/WOT??
10-09-2017 | 06:41 AM
#1
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7.4 Mag MPI Issues out of hole/WOT??
New to OffShoreOnly and looking for some help!!! I'll try to sum everything up as quickly as possible, but could really use your input! I'm running a 99' PowerQuest 260 Legend SX, 7.4 Mag MPI w/ SideMount Whipple for reference...Boat ran perfectly before everything below:
Earlier this season I blew a distributor gear...had the gear replaced and since my compression was all over the map I decided to have the engine rebuilt to avoid any potential issues (this is my first year with it and wanted to make it right). Had the engine dyno'd but couldn't get a full pull off it. Once the engine was installed back in the boat (by certified tech's at local marine service shop) and ready to roll we took it out for the maiden voyage. Well, as luck would have it the same issue was present that was had on the dyno. I couldn't get out of the hole without it dogging out, and couldn't get the Whipple to wind up WOT.
Did some wire harness tracing and found that the two plugs that hook into the ignition control module weren't hooked up properly by the engine guy. Perfect! I hooked them up properly (since i had meticulously labeled every wire prior to disassembly) and put it in the water. RAN LIKE A DREAM! Everything was back to normal. We ran it the following Saturday/Sunday with zero issue.
Well, the following Wednesday my wife and I decided to go for a cruise after work...all the sudden we're back to square one. It chokes out when trying to get up on plane, but if I ease into it I can get there, and it will run well at cruising speed. But, if I try to get to WOT after that, the supercharger won't wind up and it wants to cut out!
I've changed plugs, water separator, new distributor cap and rotor. Found out how to time the engine properly by putting the paper clip jumper in the DTC connector after running up to 1600 (entering base timing mode) and then setting timing to 8 degrees BTDC. Zero success...Anybody had this before??? I'm guessing the next things are checking spark and fuel pressure on the rail? HELP!!
Earlier this season I blew a distributor gear...had the gear replaced and since my compression was all over the map I decided to have the engine rebuilt to avoid any potential issues (this is my first year with it and wanted to make it right). Had the engine dyno'd but couldn't get a full pull off it. Once the engine was installed back in the boat (by certified tech's at local marine service shop) and ready to roll we took it out for the maiden voyage. Well, as luck would have it the same issue was present that was had on the dyno. I couldn't get out of the hole without it dogging out, and couldn't get the Whipple to wind up WOT.
Did some wire harness tracing and found that the two plugs that hook into the ignition control module weren't hooked up properly by the engine guy. Perfect! I hooked them up properly (since i had meticulously labeled every wire prior to disassembly) and put it in the water. RAN LIKE A DREAM! Everything was back to normal. We ran it the following Saturday/Sunday with zero issue.
Well, the following Wednesday my wife and I decided to go for a cruise after work...all the sudden we're back to square one. It chokes out when trying to get up on plane, but if I ease into it I can get there, and it will run well at cruising speed. But, if I try to get to WOT after that, the supercharger won't wind up and it wants to cut out!
I've changed plugs, water separator, new distributor cap and rotor. Found out how to time the engine properly by putting the paper clip jumper in the DTC connector after running up to 1600 (entering base timing mode) and then setting timing to 8 degrees BTDC. Zero success...Anybody had this before??? I'm guessing the next things are checking spark and fuel pressure on the rail? HELP!!
10-09-2017 | 10:28 AM
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From: Ft. Worth TX
engine scan
look at map readings
fuel pressure testing on the water thru out all rpms
run this engine on the water with a remote gas supply hook to the first fuel inlet engine side. This eliminates the BOAT SIDE for any fuel delivery issues or pin points your problem is the boat side.
how solid is compression
look at map readings
fuel pressure testing on the water thru out all rpms
run this engine on the water with a remote gas supply hook to the first fuel inlet engine side. This eliminates the BOAT SIDE for any fuel delivery issues or pin points your problem is the boat side.
how solid is compression
