1986 5.7l volvo Penta - Fueling Issue?

Good evening,

Been browsing forum but found no specific examples of the problem I have... so here I am!

Have a Volvo Penta 5.7 with a 290 z drive from circa 1986.

Bought the boat fairly recently and needed some work, new floor, interior seats etc. Engine appeared some what OK if not grubby.

Anyway, I took the boat out for the first time and ended up being towed home. Engine was ok for about 45 minutes, then bogged down and would not idle properly at all. Once running, it wouldnt get about 2000 rpm, then would just stall.

Anyway, to cut a long and arduous story slightly shorter, I have completed Following in no particular order

New fuel pump
New fuel Lines
Removed any restrictions in fuel line
New spark plugs
new Oil Filter + OIl
Cleaned and decrudded dstributer cap + cables but not replaced
Cleaned Carb and readjusted

Boat went back out on the water after the initial problem and was seemingly OK, but after about 40 minutes of slow running through and estuary and back went to throttle up and it just wouldn't....

Gets to about 2000rpm and no further, just bogs down, coughs splutters and gives some interesting backfires!

Had a tinker in the shop, and it runs perfectly idles great with around 18g or mercury at Idle at around 900rpm. Picks up fine under no load and revs great. A soon as you load the boat, the problems occur. Feels like a fuel starvation issue, but I have adjusted everything and fuel delivery at carb is more than substantial.

I'm no major expert with holley carbs, but believe I have this setup correctly given what I have read around the web. I believe Its a 4160 based carb list 80309 if anyone is interested.

I'm fairly certain its a carb issue, given that nothing else has otherwise changed, Dizzy cap is in the same place and does not move so ignition timing is ok although I haven't actually checked the actual timing, vacuum advance moves correctly. I haven't had the guts of the distributor apart yet but have no real reason to suspect this, the whole things is integral as far as I can see as there is no coil. I have a vacuum gauge that I fitted to the boat, under WOT the vacuum drops as expected to next to nothing, the boat will not pick up under partial throttle and any sort of gentle throttle increment its just bogs at around 2000rpm The gauge is otherwise stable, (apart from the occasional misfire).

Would appreciate some advice if anybody has any ideas!

Thanks

Jody

Jody, I am reading here about the things that you've done and the measures that you've taken, but the most troubling thing is what you've NOT done!

But I'll digress for the moment.

Tofts said:

Have a Volvo Penta 5.7 with a 290 z drive from circa 1986.

Anyway, I took the boat out for the first time and ended up being towed home. Engine was ok for about 45 minutes, then bogged down and would not idle properly at all. Once running, it wouldnt get about 2000 rpm, then would just stall.
Was the ignition coil heating up excessively?

I have completed Following in no particular order

New fuel pump
New fuel Lines
Removed any restrictions in fuel line
Did you remove and clean the fuel tank pick up tube and/or look at the screen on the bottom of the tube?
New spark plugs
Correct heat range and reach?
new Oil Filter + OIl
Cleaned and decrudded dstributer cap + cables but not replaced
Cleaned Carb and readjusted

Boat went back out on the water after the initial problem and was seemingly OK, but after about 40 minutes of slow running through and estuary and back went to throttle up and it just wouldn't....

Gets to about 2000rpm and no further, just bogs down, coughs splutters and gives some interesting backfires!
Any audible signs of detonation or reasons to believe that it could be undergoing detonation?

Had a tinker in the shop, and it runs perfectly idles great with around 18g or mercury at Idle at around 900rpm. Picks up fine under no load and revs great.
This is a non productive test. The engine must be loaded in order to gain any valuable info.

A soon as you load the boat, the problems occur. Feels like a fuel starvation issue, but I have adjusted everything and fuel delivery at carb is more than substantial.

I'm no major expert with holley carbs, but believe I have this setup correctly given what I have read around the web. I believe Its a 4160 based carb list 80309 if anyone is interested.
Try using the P of E.... process of elimination.
If you can borrow a like carburetor, give it a try.

I'm fairly certain its a carb issue, given that nothing else has otherwise changed, Dizzy cap is in the same place and does not move so ignition timing is ok although I haven't actually checked the actual timing, vacuum advance moves correctly. I haven't had the guts of the distributor apart yet but have no real reason to suspect this, the whole things is integral as far as I can see as there is no coil.


OK.... this is where I was heading earlier.

First off...... a Marine Ignition distributor will NOT include vacuum advance. If your distributor has a vacuum diaphram on it, this would be an Automotive ignition distributor, and it must be removed ASAP.


You make no mention of having checked to see where the Progressive Advance is, nor where the TA is (TA = total advance).
This is very important for the gasoline Marine engine.
Incorrect ignition advance may lead to Detonation..... of which is a very destructive force.


I have a vacuum gauge that I fitted to the boat, under WOT the vacuum drops as expected to next to nothing,
And that is one reason why the Marine Engine does not benefit from Vacuum Advance.

The automotive ignition distributor will be illegal for Marine use when/if used within an enclosed engine bay.
The advance curve will be incorrect for the Marine engine.
Incorrect excessive advance may lead to Detonation..... of which can be very destructive to the gasoline Marine Engine.

I would advise that you see your OEM ignition advance specs/curve, and then check your current progressive and TA against it.

Jody

Click to expand...

.

Ok. You make interesting comments as I was not aware of the distributor advance being illegal. But, is that the case in the UK? As I live across the pond from you! But why is it illegal?

That being said, it all adds up that thus is not the original engine. The wiring loom was cut and spliced, controls seemed extra and a few odds and ends didn't add up. Anyway.

Unsure if the coil got hot. Will check next time.
Pickup was removed and screen was buggered, so removed and fitted an external in line filter instead.
Heat range was same as original plugs. Ngk BR6ES from memory.
Detonation, none at all afaik.
Sadly, no cars/boats to borrow. The marine shop barely uses anything American so knows little about them.
Okay, will remove advance line and plug. But why? What should my timing be?

Thanks for the comprehensive reply, it's the first info I've had where somebody actually seems to know something.

............................

Tofts said:

Ok. You make interesting comments as I was not aware of the distributor advance being illegal.
The automotive distributor advance is legal (not smart.... but legal), however, the unit itself is not legal when used in an enclosed engine bay.
The approved Marine Ignition system will be spark supressed.


But, is that the case in the UK? As I live across the pond from you! But why is it illegal?
As said, the automotive gasoline engine ignition distributor is not Marine Approved against electrical spark potential.

These non-arrested or non-contained electrical sparks are just as dangerous in the UK as they are in the US.

That being said, it all adds up that thus is not the original engine. The wiring loom was cut and spliced, controls seemed extra and a few odds and ends didn't add up. Anyway.

Unsure if the coil got hot. Will check next time.

Pickup was removed and screen was buggered, so removed and fitted an external in line filter instead.
I could not recommend one of the in-line fuel filters. There's no need for these when the Marine cartridge style filters will do the job much more efficiently.

Heat range was same as original plugs. Ngk BR6ES from memory.
See your OEM specs.

Detonation, none at all afaik.
Detonation is not always audible.
BTW... pre-ignition and detonation are completely different from one another.

Sadly, no cars/boats to borrow. The marine shop barely uses anything American so knows little about them.
Okay, will remove advance line and plug. But why?
As eluded to earlier, the Marine engine will not develope any usuable manifold pressure (vacuum) while under Marine Engine loads.
During these heavy loads, throttle plates are very much open.

What should my timing be?
See your OEM ignition timing specs and advance curve.
Post the info, and I will explain how to check and see if the new replacement ignition system is offering the correct curve.


Thanks for the comprehensive reply, it's the first info I've had where somebody actually seems to know something.

Click to expand...

Just today found the performance issue with my volvo 570. This I believe is a similar power package as yours. Problem turned out to be fuel pump inlet check valve. I know you said you replaced the fuel pump. The holly carb and the hard lines make testing fuel pressure at WOT difficult. Years ago I was factory certified by volvo marine. My trouble started with top end performance immediately after a tune up. I spent 4 years chasing it thinking it was some how related to that tune up and left me"blinded" to always follow the simple rules: Fuel, spark, and compression in their correct amounts at the proper times. During my "blindness" I changed the manifolds, rebuilt the heads, dissembled the carb (glad I did. Discovered a stuck accelerator pump check valve. Did not fix the top end problem but did perform better when rapid throttle changes!) I ran the boat at the lake with an oscilloscope attached. Ignition was perfect. Then last year my fuel flow meter indicated flow variations and eventually that trip to lake Powell was ruined by a fuel delivery failure. Lesson learned. Install the pressure gauge, install the inlet suction gauge