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06-14-2019, 06:08 AM #1
5.7 Sterndrive "dieseling", and sucking in water,
I have a buddy of mine has a 1998 Volvo Penta 5.7 GS SX, He rebuilt the engine, stepped up the compression a bit.(I also know that stepping up the compression increases your risk of water ingestion.)
The engine has been is service for a year with no issues, and runs great.
Recently, after winter storage, he launched the boat and now she has a habit of "dieseling" after he shuts her down.
The engine has sucked water into the cylinders as a result. Forunately , he's on a lake, and removed the plugs and blew out the water. The engine is fine.
My question is, what causes the dieseling, and what to look for to prevent it?
Anyone with experience with this problem, I'd sure like to hear from your thoughts.
Thanks!
Boats are like Potato Chips..You can't have Just One1
1974 Hiliner Gypsy 260 Volvo SX
1972 Hiliner Adventurer CC 200 Evinrude OceanPro
1994 Sea Nymph 1462 25 Evinrude
1989 Boston Whaler 13 w/40, then 50 Johnson (sold)
1970 Wellcraft V-20 Steplift, Evinrude 155 Commercial (sold)
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06-14-2019, 06:16 AM #2Screaming And Flying!
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A couple things could , first run out or drain all the regular gas and use 91 or better since you have upped it's compression. Then check the warm idle speed and check for a bad intake vacuum line sucking air. What temperature is it running when hot?
Last edited by FMP; 06-14-2019 at 06:19 AM.
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06-14-2019, 07:05 AM #3
she's running 180 degrees when she's warmed up.
Boats are like Potato Chips..You can't have Just One1
1974 Hiliner Gypsy 260 Volvo SX
1972 Hiliner Adventurer CC 200 Evinrude OceanPro
1994 Sea Nymph 1462 25 Evinrude
1989 Boston Whaler 13 w/40, then 50 Johnson (sold)
1970 Wellcraft V-20 Steplift, Evinrude 155 Commercial (sold)
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06-14-2019, 07:10 AM #4Screaming And Flying!
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When you come back in after a good run , your heads are hot. The extra compression with that will diesel the weak fuel when you shut down.
Your probably knocking a bit under hard acceleration etc as well. Check your tuneLast edited by FMP; 06-14-2019 at 07:14 AM.
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06-14-2019, 07:11 AM #5
A little cooler thermostat will help , one step cooler spark plug , couple of degrees less timing , low as possible idle rpm , let motor idle a bit after a hard run prior to shut off to cool piston crown temp . The better fuel will also help . Hf...
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06-14-2019, 07:18 AM #6Screaming And Flying!
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Start with the best fuel, that should do it unless you went crazy with the compression
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06-16-2019, 08:39 AM #7Screaming And Flying!
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...or just shut it off in gearlol
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06-16-2019, 09:22 AM #8Banned
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06-16-2019, 05:16 PM #9
Did he change the exhaust?. Can be water inversion and sucking water back in the exhaust. You have a oil temp gauge?.
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06-16-2019, 08:20 PM #106000 RPM
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If it’s injection an injectors leaking.
Slipped timing chain can also start inversion.
But it could be a head gasket leak.
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06-24-2019, 05:23 AM #11
The ingestion issue has gone away, but after idling thru a no-wake zone after about 5 or 7 minutes, the engine, on its own, will start to increase idle rpms all by itself, without touching the throttle.
There is no vacumm lines to leak, becuase the Holley 850 has mechanical secondaries, if there was a manifold or carb base leak, the engine would not idle well at all.
My theory is this:
Since the double pumper keeps the secondary bowls full at all times, even at idle, Could a float be sticking to the point its starts to dribble fuel into the intake? thereby increasing engine rpm without any advance on the throttle?
When the engine is shut down, it diesels, but not to the point of water ingestion.
Am I on the tright track? or am I all wet?
Again, this engine had none of these symptoms last year, it ran great with no issues.
Big Tom, The exhaust is stock.
So I don't see how the timing could effect it,
One last thing guys, can somebody please tell me what adjusting the "dizzy" is?Last edited by C.C.Hiliner; 06-24-2019 at 05:25 AM.
Boats are like Potato Chips..You can't have Just One1
1974 Hiliner Gypsy 260 Volvo SX
1972 Hiliner Adventurer CC 200 Evinrude OceanPro
1994 Sea Nymph 1462 25 Evinrude
1989 Boston Whaler 13 w/40, then 50 Johnson (sold)
1970 Wellcraft V-20 Steplift, Evinrude 155 Commercial (sold)
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06-24-2019, 03:44 PM #12
Get the 180 stat out of there. You should never see more than 140 degree's on a stock motor. When running big block modded motors I don't use stats, I run restrictor plates and keep temp down around 100 degrees. I would run a oil temp gauge instead and watch that oil gets hot enough to burn condensation out of it. In the great lakes with colder water the motor would sweat. Set timing @ 10 degrees BTDC at idle for starters. As for total advance I have always ran big block @ 28 to 32 degrees at 2200 rpm . Not sure on small blocks. Get idle down as low as you can with out stalling when shifting into gear with motor warm. Check float level by taking out side inspection screws on side of float bowls.(prob a youtube video on how). After shutting off watch the carb and see if theres any vapor/smoke coming up from carb. This would mean its bleeding over after shut down. YOU are running a marine Holly carb right ? with the over flows?. IMO a 850 carb is way to big for a 5.7 even with mods.
What exhaust are you running?Last edited by big tom; 06-24-2019 at 03:52 PM.
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06-25-2019, 01:05 PM #13
It's a 750, not an 850, Tom
He's running the stock underwater exhaust
Boats are like Potato Chips..You can't have Just One1
1974 Hiliner Gypsy 260 Volvo SX
1972 Hiliner Adventurer CC 200 Evinrude OceanPro
1994 Sea Nymph 1462 25 Evinrude
1989 Boston Whaler 13 w/40, then 50 Johnson (sold)
1970 Wellcraft V-20 Steplift, Evinrude 155 Commercial (sold)
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06-25-2019, 03:04 PM #14
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06-25-2019, 10:29 PM #15
even a 750 is big for a small block, high idle, rich at idle can cause dieseling also......
"One of the penalties for refusing to participate in politics is that you end up being governed by your inferiors". Plato .
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