redstinger

This has happened 3 times now. Takeoff from marina, accelerates with authority, snaps on plane, cruising at 3500 rpm. After about 3 minutes, boats feels like power is dropping off...I give it more gas to bring speed back up, but the power that was there when I first took off from marina is gone. I then decelerate, and as I come down off plane, engine coughs and dies. Engine starts back up each timeand I idle back to marina. This is a brand new 489 with 3 hrs on it, Cam with 230 dur, 595 lift from Bob @Marine kinetics, 188 heads, factory refurb Holley 750, MSD coil, Thunderbolt IV ign, Holley elec fuel pump, 3/8 lines, 454 mag intake. Timing @ 10, 34 total, floats adjusted. Scratching my head in Austin (in 100 deg heat!!!) The coil (2 seasons on it) and the TBIV are the only parts which are not brand new.

firehawkcat

I would check that Msd or fuel pump I have read about more than one msd(marine stranding devise) problems on this forum

redstinger

Fuel pump is brand new also. I still have the orig Merc coil, will put it back and on and see if it fixes it. Hopefully its not the TBIV module or ign amp...I noticed they are not cheap.

teamsynergy

Check main fuel tank vent. Might be clogged causing tank to collapse partially...

tw50

iTrader: (1)

i had a boat do the same thing,if you can get to the pick up tube in the gas tank take it out and look in top thire are screens in the top 90 elbow thay get cloged i fought this for a hole season till i found it

FIXX

iTrader: (2)

Check the hall effect in the distributor,,common problem for going bad..

stinger222

pulled fuel pickup...some small trash on the screen, but not completely plugged. What is the hall effect on the distributor?? Never heard of it.

FIXX

iTrader: (2)

looks like this

http://www.go2marine.com/product.do?no=116368F

redstinger

oh, you mean the module. I always thought those things worked or they didn't. I'm going to try replacing the coil first since it seems like it is heat related. runs great cold then performance degrades until it finally dies.

redstinger

changed the coil, took it out this morning...same damn thing, starts right up, gets on plane, drive around for 5 minutes, come back to marina, start to slow down, as rpms drop below 2600 rpm, cough/spit, push throttle down, smooths out and stays running...then slow down again, engine cuts outs out. starts back up for 30 sec, idling, now I can't get it started again...pull off flame arrestor, carb is wet looking. its always started back up before. Luckily the wind blows me the last 50 yds to dock. Back in slip after 15 min, it starts back up, but dies in about 5 sec.