Volvo Penta GM 5.7 TBI low power at take-off

[spomey]

I know most people want more power in a boat, in my case I have a 23 foot sportdeck Chris Craft. the boat weighs 4400 lbs it has the duo prop. The issue is at take off all seems good, as the boat starts to move and the RPM increases it falls on ts face around 2000 RPM for a second then continues to climb again slowly. I understand I can change props but this seems to be a power issue.
another area where it lacks is if your cruising and turn sharply and lose "plane" it take a long time to recover. and sometimes it doesnt recover even with trim adjustments to full down. something else i need to test is it seems like take off is faster sometime not at full down trim.
my main question is.. for take off max torque where should I set timing?

 

[alldodge]

What VP 5.7 motor?

Is this a new issue?
Did it ever reach around 4800 rpm at WOT?
Has fuel pressure been tested?
Has a compression test been done?

 

[spomey]

The motor is 5.7 GSI (I am pretty sure although I don’t know the differences between the models)
The issue is Kindof new. I didn’t notice it on the first few trips just out paying with the new boat, then it started missing I checked compressing and 3-5 cylinders had no compression. Replaced the cracked head and now I am possibly being finicky. The most RPM that I have seen on the water was 4200-4400 but I never go max speed the lakes are just too rough and small around here.
I have not tested fuel pressure but I will. What psi should I see?
Compression is around 140. I tested the new head side and saw 128-141. (Within 10% not broken in)

 

[spomey]

When setting timing I set it right at zero. Here is a weird thing. The engine surges between 1500 and 2000 (takes about 10 seconds per surge) but the timing stays at 0. If I advance the timing it smooths out. But…. I have been reading and it seems regarding the timing adds low end torque have you heard of this? Any ideas?

 

[alldodge]

Fuel pressure should be 8+/-2 psi on low side and 29 +/- 2 psi on high side

When setting timing I set it right at zero. Here is a weird thing. The engine surges between 1500 and 2000 (takes about 10 seconds per surge) but the timing stays at 0. If I advance the timing it smooths out. But…. I have been reading and it seems regarding the timing adds low end torque have you heard of this? Any ideas?

Motor gets timed in base timing mode at 8* BTDC

To place in base timing mode find DLC connector and put paper clip or other jumper between pins A and B. If rpms do not increase when jumper is installed, bring rpms up to 1500 to 1800.

 

[Scott Danforth]

if you have the crab cap, change it.

 

[spomey]

I have the round distributor, I can set it at 8 and try it, all i could find besides what you say is set it at 0 degrees in base mode. zero was better than 2 I will say that bt I will try 8 degrees, oh BTW I am about 4500 ft in elevation if that matters.

 

[Scott Danforth]

I have the round distributor, I can set it at 8 and try it, all i could find besides what you say is set it at 0 degrees in base mode. zero was better than 2 I will say that bt I will try 8 degrees, oh BTW I am about 4500 ft in elevation if that matters.

You are down 12-15% on power just from elevation

 

[spomey]

You are down 12-15% on power just from elevation

Agree I just need to optimize what is available and if there is a simple torque /hp increase, do that. Do they have a performance chips for boats? I know I can change props but duo props are a spendy last resort

 

[alldodge]

There are no chips, but there is MEFI burn bt you need to know how to change the fuel tables

What pitch props are on it now?

 

[spomey]

I don’t feel I need a huge gain just a bit for tubes and wakeboards so they can pop up, and not drag along, I don’t use top speed at all.

There are no chips, but there is MEFI burn bt you need to know how to change the fuel tables

What pitch props are on it now?

I don’t know they are F5 front and rear and I don’t know anything about duo props or Volvo stuff

 

[Scott Danforth]

There are no "chips" the motor is already putting out a fair amount of power. To put out more you need to go bigger with the motor, change cam, or you can add a blower..... All will require the use of MEFI burn and remap the ECM

Drop to F4 props

 

[alldodge]

oh yes VP stuff

 

[spomey]

oh yes VP stuff

For the timing… I get confused, there is a stationary “v” on the engine, and the engine rotates CCW (damn I think) so I move the distributor so the vibration damper mark moves 8 degrees to the right of the v notch 8 degrees, I think there are 2 degree marks on the vibration damper. Is that BTDC? Mark on the v is TDC? Just checking

 

[alldodge]

Mark is TDC
Left hand motor rotates CCW looking at rear of motor. Looking at front it rotates CW so each mark is 2* to the right of the notch

 

[spomey]

Mark is TDC
Left hand motor rotates CCW looking at rear of motor. Looking at front it rotates CW so each mark is 2* to the right of the notch

Just to make sure I understand I am looking at the rear of the motor, I want to move the 4th mark to the right of the large line to the v, in base timing mode. Why is it so different from truck timing?

 

[spomey]

Just to make sure I understand I am looking at the rear of the motor, I want to move the 4th mark to the right of the large line to the v, in base timing mode. Why is it so different from truck timing?

Wait I read what you too many times now I am really confused lol. What do you mean left hand motor? I will take a picture of what I have then I can’t over think it !

 

[Scott Danforth]

Your motor is a left hand rotation motor

 

[alldodge]

To be simple, your motor is rotating CW looking at the front
You need 4 of the marks to the right of the notch

 

[spomey]

got it! move the 4th mark on the right to the V notch! I thought that but after talking advance and retard timing CW CCW front back I get mixed up! thank you for straightening me out. I have read a few posts stating that slightly retarding the timing increases low end torque while sacrificing top end. howevrer my understanding of the combustion process is the opposite. that you actually want to run as much advance as you can without pre-detonation. what are your thoughts?