Volvo Penta 5.7 no power

mkor

Seaman Apprentice
Joined
Mar 29, 2023
Messages
43
Continuing to my previous repair with looking for a spark, now I have a spark, the motor is running. But today I couldn't get into planning mode. I do not have enough power, for some time I was looking for the cause in the wave and the tidal current, but no, this is a mistake.

So, I give full throttle, the boat accelerates to 12 knots and cannot get into planing mode. Turnovers of 2800 and above do not rise, but if I turn off the gear, then I calmly spin the engine to the maximum. I dived, nothing was wound up, the propeller is spinning by hand in neutral, the bottom is practically not overgrown.

I think the problem is the loss of power, I do not know what is connected with.
I started to listen and it seemed to me that the engine troit.
I removed the spark plugs and they look good. I found 2 wires under the cap which had small traces of corrosion, cleaned them.

Until the problem is solved, any ideas?
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
49,538
What are your compression numbers?

What trouble shooting steps have you taken?

Is this a new problem? Or a new to you boat ?
 

dubs283

Vice Admiral
Joined
Jul 27, 2005
Messages
5,322
If you have spark and the engine runs although poorly especially under load you should inspect the fuel delivery system

Filters, fuel pump(s), supply, etc...

Have you confirmed ignition tune up/spec?
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
13,446
Carb or FI, electronic, or mechanical Spark Advance?
 

mkor

Seaman Apprentice
Joined
Mar 29, 2023
Messages
43
And so, a little background, for 2 years of owning a boat this happened for the first time. At first I lost power even at idle, but the problem was in the high pressure pump. I changed it and immediately went to the glider. True, I periodically added speed or disappeared and the engine worked intermittently. It didn't happen last season. I don't know which manufacturer I bought the pump, but it's not original. I measured the pressure on low and high. Low 11 and drops if you do not start the engine, high 48 + -1 and stableю If you add speed, the pressure of the injection pump dropped to 46.

If you turn off the engine for 2 hours, the pressure does not drop.

If you set 1200 rpm and the speed starts to float, I see how the monometer needle floats by 1-2mm.

Checked the anti-siphon valve, it opens well.

I have nothing to measure compression.

From the rest, replaced:
Throttle position sensor
Ignition coil
ignition module
Distributor with cover, rotor and sensor

Idling is excellent.
Low revs from 1000 to 1500 - revs float, as if the engine is troiting.
RPMs above 1500 without load are fine.
An attempt to get into the glider - 2800 rpm and 12 knots, no more.
 

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mkor

Seaman Apprentice
Joined
Mar 29, 2023
Messages
43
I took pressure again today and made a video.
My book says normal high pressure is 50-60, mine is slightly lower. At the same time, they write about 45psi on the forums.
 

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