Engine won't reach WOT - on new engine

[alldodge]

Today, we installed a new ignition module (a copy - not the original Indmar spare part) using a factory timing shunt. Set base to 10 BTDC and advanced showed only 22. Rev'ed the boat while in water and the boat was able to accelerate and go to >30kn, however, if applying full gas, it would backfire during accleration.
So the mechanic manually adjusted the distributor to advanced 32 (base then at 20 BTDC) and the boat accelerated perfectly and >35 kn).
Will test of the boat starts tomorrow when cold.

Is it OK to have the base time set so high?

Do you recommend getting the original Indmar timing module instead?

My Opinion:
Something is not right, the GM 5.7 is a GM 5.7 and it makes no difference if Indmar, Merc or VP is using it. Base timing is should be set at 10 BTDC and the reason is so it does not burn a piston. Your only getting 10 degrees

Maybe not everyone, but I need to start over from scratch to verify some things.
What year was the original motor?
Which distributor is installed?
Which carb is installed?
This was a new reman motor, but with all the issues, has anyone check to make sure the motor was put back together correctly (timing gears)?

 

[aquador]

My Opinion:
Something is not right, the GM 5.7 is a GM 5.7 and it makes no difference if Indmar, Merc or VP is using it. Base timing is should be set at 10 BTDC and the reason is so it does not burn a piston. Your only getting 10 degrees

Maybe not everyone, but I need to start over from scratch to verify some things.
What year was the original motor?
Which distributor is installed?
Which carb is installed?
This was a new reman motor, but with all the issues, has anyone check to make sure the motor was put back together correctly (timing gears)?

1. The orginal engine (a Volvo Penta 4.3GL) was from 1998.

2. I checked the Barr spare part catalogue and the spare part number is 550002 (it appears to be Electronic Ignition Distributor Kit Delco EST Marine V8 GM 305 350 454 502)

3. The original carb from Barr was a Holley 600 CFM/4barrel, but it was replaced with a Edelbrock performer marine carburetor 600 CFM 1409.

4. The engine was brand new - not reman or a service block (http://www.barrmarine.net/57l-bobtail-carbureted.html). It is labelled "5.7 L VR CARB I/O P/S F/WATER". I believe the block was manufactured in 2013.

For my understanding what do we need to do to check "the motor was put back together correctly (timing gears)"?

 

[Bondo]

We removed the flame arrester with running under load and we noticed a clear backfire.

Ayuh,.... That's usually a sign of a Lean condition,.....

 

[alldodge]

The EST distributor should supply 18 degrees of advance timing. The lack of advance would have me looking at the distributor. The module is the same from 3.0 to 7.4 motors. If your using the original 4.3 distributor then this could be the issue. The 4.3 uses around 10 degrees of advance, the 5.0 and 5.7 use 18 degrees

Also agree, with getting a backfire under higher load and rpms then your carb may be running lean.

It probably isn't the timing gears, but if everything checks out, I would bring the motor around to TDC on number one cylinder. See if the intake valve closed before the piston comes up on compression stroke and stays closed as it goes back down. Then the exhaust would open

 

[aquador]

The EST distributor should supply 18 degrees of advance timing. The lack of advance would have me looking at the distributor. The module is the same from 3.0 to 7.4 motors. If your using the original 4.3 distributor then this could be the issue. The 4.3 uses around 10 degrees of advance, the 5.0 and 5.7 use 18 degrees

Also agree, with getting a backfire under higher load and rpms then your carb may be running lean.

It probably isn't the timing gears, but if everything checks out, I would bring the motor around to TDC on number one cylinder. See if the intake valve closed before the piston comes up on compression stroke and stays closed as it goes back down. Then the exhaust would open

Today, I drove the boat for about 1,5 hours. It started better than ever, always on the frist attempt, and accelerated fine up to 35 kn. No backfire, hesitation or other unusual noise. Big thanks to everyone who provided advice here!

1. The new engine is complete; no parts except the exhaust from the orginal were used. So you believe, the base should be 10 and advanced +18, i.e. 18 total advance or total 28? Could the previous mechanic have put back the distributor wrongly?

2. I will try your other suggestion, thanks.

 

[alldodge]

18 total advance or total 28?

Correct

Could the previous mechanic have put back the distributor wrongly?

Either that or the weights are hung up

Keep an eye on your spark plugs