5.7L TBI (1994)- Flat Tappets

[CatawbaRinker]

Long story short I had to have a rebuilt engine installed in my boat, original engine is a 1994 5.7L Bravo TBI, serial # OF286058. I have had absolute horrible luck with the mechanic that I've been dealing with and he recently threw another zinger at me. When he had me order the new rebuilt 350 long block he failed to mention that the old one had roller cams instead of flat tappets. Even after I received the engine and he installed it he never mentioned the difference.

The boat is now in the water and runs great, however I cannot get RPMs above 3200. So far the only thing I've checked is fuel pressure which was steady at 30 PSI and I'm going to spend the weekend going through the checklist, however I guess I'm just looking for a piece of mind that the flat tappets wouldn't take away 1,200 RPM and power. I know there is increased performance with the rollers, but I would imagine the engine should still be able to get up and go with the flat tappets. I'm leaning towards a timing issue.

 

[Scott Danforth]

look at your fuel system. first, your fuel pressure is good...... however have you taken a fuel sample? is is pure fuel or does it have crud in it.

what is your compression?

only a few motors prior to 1996 had roller cams even though the block was prep'd since 1988.

the stock cams in boat motors is so mild, there is not much of a difference between flat tappet cams and roller cams

 

[alldodge]

Does the fuel pressure stay at 30 psi as rpms increase?

Has timing been set at 8 BTDC in base timing mode?

 

[CatawbaRinker]

So an update since last time.

I switched fuel filter, found no signs of moisture or gunk. I have tried to adjust timing, bought the Mercruiser timing tool however when I connect it the boat will not fire. The injectors spit fuel when I turn the key and it turns over, but will not fire. I've also noticed a ticking sound when I plug the timing tool in. Sane result if I hook up using a paper clip. It will spit off codes 12 and 42. With the code 42 I switched the ICM and checked wires to ECM but no difference. Without being in service mode I still advanced thetthe to 8.

Then I took the boat for a cruise, no difference. However when I have help and I can turn the distributor under load I can get the RPM's up to 3,500 which is better. I ran out of daylight before I had a chance to go farther.

1) Would anyone know why my boat won't start in service mode?

2) Could it be the timing for the rebuilt engine could be far past the 8 BTDC?

 

[alldodge]

The motor is started then the pins A and B are connected together with paper clip or timing tool

Trouble Code 42 indicates that there may be a malfunction in the Electronic Spark Timing (EST) system.

During cranking, the timing is controlled by the ignition module while the ECM monitors the engine speed. When the engine speed exceeds 400 RPM, the ECM sends a BYPASS signal to the ignition module which switches the timing to ECM control. The ECM calculates what the timing should be then "tells" the ignition module via the EST circuit.

An open or ground in the EST circuit will stall the engine and set a Code 42. The engine can be re-started but it will run on ignition module timing. [h=4]The conditions for setting code 42 are:[/h]

• System in BYPASS mode but the ignition module is still controlling timing
  - or -
• Engine speed > 600 RPM with no EST pulses (ECM controlled timing) going to the ignition module for 200 msec.

 

[CatawbaRinker]

alldodge thank you for the reply! I was able to replace the ICM, reset the code and put the boat into service mode and set the BTDC. The good news is, the code did not come back. The bad news is the boat had absolutely no power. RPM's would hit 2800 and then just drop to 2600 and would not hit plane. I had help with me, so we were able to move the distributor and advance timing. We moved it to where I can shoot right up on plane, however WOT is it around 3,900 RPMs instead of the specified 4,400 to 4,800. We advanced slowly until we lost performance. However I am unable to even see the timing markers on the balancer now, but I have a boat that gets on plane.

I am going to do another compression check. When the new rebuilt engine was put in a month ago all 8 were in between 170-175. However before things went south earlier this year I have no idea where the timing markers were.

 

[Scott Danforth]

check your damper, your outer ring may have moved.