stbd 454 340/mei merc.

alexander38 · Post by **alexander38** » Fri Aug 07, 2009 6:19 am

Here's the trouble. engine will not run at w.o.t. the r.p.m. goes up and it drops right off and won't come back up.It will run at about 2k rpm just fine.
and it acts the same on the port tank,And the port engine runs fine on the stbd tank.

things that already have been done.
new filters
tune up
new carb.
and did a squeeze test on the cylinders and all come up to 137 psi plus or minus 4 pounds. eng. has 905 hrs on it.
my thoughts are weak fuel pump, or the ecm (more or less a timing spark box.) it's an 1987 with MEI has gone bad and won''t advance the timing.

Wes · Post by **Wes** » Fri Aug 07, 2009 8:46 am

Sounds like the same trouble I'm having with my starboard 454. It runs fine at idle and then when I try to accelerate she will die (vapor lock?) If I pour fuel into the carb and get her running again she'll run fine the rest of the day. The only thing I haven't changed is the fuel pump. It is a pain to get to. I might try an electric fuel pump after the rendezvous.

alexander38 · Post by **alexander38** » Fri Aug 07, 2009 11:58 am

Nope not vapor lock. It'll run all dall long at 14 knots but try to push past that it falls on it's face.It's like to much gas is being dumped down it but I know that's not it. It just feels that way.

prowlersfish · Post by **prowlersfish** » Fri Aug 07, 2009 12:07 pm

I throw this out , pluged or restiction in the fuel line or valves , fuel pump
anothe filter you haven't found ( many have 2 or 3 )

alexander38 · Post by **alexander38** » Fri Aug 07, 2009 12:23 pm

Ill check that out. Fuel line is a maybe.

duchess · Post by **duchess** » Sat Aug 08, 2009 6:03 am

anti siphon valve at the fuel tank?

alexander38 · Post by **alexander38** » Sat Aug 08, 2009 6:18 am

If it was anti-siphon valve would it also act up on port engine running on the stbd tank ? But I'll check it again when I'm looking at Paul's thoughts today.

prowlersfish · Post by **prowlersfish** » Sat Aug 08, 2009 8:20 am

If its not the hose/valves and you thing it could be the ecm you could swap parts from the other engine and see if the proplem moves to the other side .

RWS · Post by **RWS** » Sun Aug 09, 2009 8:58 am

there's also a filter in the fuel inlet of the quadrajet carb.

Three filters total on the International.

RWS

alexander38 · Post by **alexander38** » Sun Aug 09, 2009 10:31 am

Ok here's what I did this weekend
All 3 anti-siphons work.
Fuel fitters are clean and no water.
Timing at 11 degrees before TDC.
But one thing on that everything I've read on thunderbolt IV high energy ignition said to ground a purple wire. The only on it goes to the coil. Gray wire to coil. Red and white / green and white go to dis/cap. And some info called for a purple and white comming from in that needed to grounded but there's not one on the d*#* thing. The reason for grounding is to set base time and the ecm won't try to override you when you adjust it. Any thoughts ?

alexander38 · Post by **alexander38** » Sun Aug 09, 2009 10:35 am

Some words may get mis-spelled sorry doing this on my black-berry. And the clare is hel# to day.

RWS · Post by **RWS** » Sun Aug 09, 2009 12:04 pm

another item to check is the MECHANICAL spark advance.

I found mine partially inoperable when I bought the boat.

The use of an ADVANCE timing light with an advance knob helped me to confirm and fix that problem.

RWS

alexander38 · Post by **alexander38** » Sun Aug 09, 2009 2:01 pm

no springs or weights on the thunderbolt IV system.

guglielmo6160 · Post by **guglielmo6160** » Sun Aug 09, 2009 3:16 pm

I had a similar problem as most of you guys know, check your fuel delivery,, I had a pain in the ass foward tank delivery line that was messing up my days one to many times, now its perfect, the fuel delivery has to be perfect or that symptom will result

alexander38 · Post by **alexander38** » Wed Aug 19, 2009 4:12 am

Hey guys replaced the gas pump today, after trying everything else what a p.i.t.a. but its done. the engine sounds like a new one.

Still have to take her out and do a run but it reacts a whole lot better.

I do think the old pump was bad. I can push the pump by hand and the new no way in he(! I just hope it's fixed. been fight this for 2 months. still going to replace the coils they've got to be tried, thoughts on high out put JEG's or MSD's

Still have know ideal how to set up the thunderbolt IV mei for timing. I did find out they made two of them. I've got the first ones they made with just 4 wires then it switched to a 5 wire the 5th wire is for timing. I'm thinking about getting a advanced timing light and check total timing and see how it looks. I don't hear a miss in it when I sit base 11 btdc I just want to know it's right.

and thanks for the in put