2007 Volvo Penta 5.0 GL-H

Watty33

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May 30, 2015
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I have a strange problem when the boat is up to speed. For a split second, I lose RPM which is then regained. I don't have to touch the throttle for this to happen. It's almost like someone has put their hand over the carb and then lifted it. Or kinked the fuel line and let go. I've read about the fuel pumps being a problem but that seems to me more with the injected motors. I'm considering wiring the choke in place to make sure the butterfly is not closing and opening. Anyone have any ideas?

I didn't touch the motor since I purchased the boat 2 years ago. This issue continues after a carb rebuild due to a leaking plug. New cap and rotor. Fuel filter changed last year and I don't put more than 20 hours on the motor in a year. Issue is intermittent.

Thank you!
 

Watty33

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https://youtu.be/slRVS8ecs68

You can hear and see the issue on the tach. Then I throttle up and it stops. However, it does the same thing at any higher RPMs. My tach needle jumps around, another issue for another day.
 

alldodge

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Your loosing an electrical connection. It took me a few times of watching the vid to notice the fuel and oil gauge also move. When you throttle up from 40 to 50 mph there is a spot where the gauges move also. If your vid showed the whole dash it would be more noticeable.

I would start by cleaning connections and make sure their tight
 

Watty33

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Any connections in particular? Ignition, relays, etc? I know my battery connections are tight.
 

alldodge

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I would check the engine harness connector, grounds on the block and if there is one behind the helm, even key switch. Watch the voltmeter and see if it to moves
 

Bondo

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Ayuh,.... Welcome Aboard,.... I'd check the contents of the fuel filter for anything but fresh clean gasoline,....
 

Watty33

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Update:

I dumped the fuel filter in a clear container and nothing but clean gas. I check all the connections that I could, including watching and listening for plug wires grounding out and found nothing. This is an Arizona boat and as a former mechanic I know that corrosion in electrical connections out here is rare.

Took the boat out tonight in hopes that moving the connections around would fix this but same issues are happening.

ALSO, I've notice a few things. 1. I'm getting the sign that the impellor housing is going out as there is a "ring" on the motor cover and in the inside of the engine compartment - like it's throwing material. 2. It sounds to me like the gimbal is on the way out. When I gas it up in neutral with the wheel turned all the way over, you can hear a noticeable sound. 3. When I shut the engine off, it sounds to me like the water is draining out of the manifolds and motor. I've never heard this before. We were on the water for an hour and there was a little water showing down below - possible leak towards the back of the motor?

At my wits end as I'm fairly capable when it comes to diagnosing and fixing issues. I'm stumped and not sure if the 3 issues above have anything to do with my problems.

- https://youtu.be/Zb_aT70Dy0E video of the idle bouncing around after coming off plane. It settles down after a while and is intermittent.

- https://youtu.be/Zb_aT70Dy0E video on plane and at 20 seconds in you can really hear the intermittent bogging.

I watched the voltmeter and it doesn't move when these issues are occurring. The fuel gauge has always bounced around since day 1.

Anyone have a recommendation for a Volvo mechanic in Phoenix that really knows their stuff???
 

alldodge

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Still seeing signs of a bad ground. Your oil pressure gauge is showing 80 psi, if this was happening the seal on the filter would start to leak. The US standard ofr gauges is 33 zero and 240 full scale. So if the sender wire was removed from the sender it would go full scale. The bouncing of the fuel gauge will also lean me to a bad ground.

The motor up/down sounds like your not getting a full supply of fuel. The rpm change could also be from a bad ground on the distributor and/or pickup module. The new modules for the EST distributor come with an extra ground wire.
 

Watty33

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I had an hour meter installed last year. Did some poking around tonight and noticed the positive lead was vamped to the coil wire. Going to unplug and see if it clears it up.

Where should this lead be hooked into instead of the coil wire? Oil pressure sender or will that give it a bad reading?
 

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Bondo

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Ayuh,.... It needs to be hooked to the ignition circuit,.... It oughta be fine where it is,....

The oil pressure sender is a varying ground, not a power wire,.... the sender/ gauge measure ground resistance,...
 

alldodge

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I had an hour meter installed last year. Did some poking around tonight and noticed the positive lead was vamped to the coil wire. Going to unplug and see if it clears it up.

Where should this lead be hooked into instead of the coil wire? Oil pressure sender or will that give it a bad reading?

The connection to your hour meter shouldn't have any effect normally, but if the hour meter is having an issue it can reduce the power going to the coil. This pic is just for reference showing the purple wire connection on the EST distributor

Delco EST 4 cyl.jpg
 

ed_hall1

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Jul 29, 2002
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My first immediate impression after watching your video is a fuel related issue. If fuel injected, make sure you run some fuel injector cleaner through the engine and also run a premium grade non-ethanol gasoline. Water in the fuel can also cause similar issues. You should also double check any vacuum hoses for deterioration or loose connections.
 

Jeepster04

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Jan 5, 2009
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When was the last time you changed the plugs? Our 06 GL-G had the original plugs as of 2015. It was doing something similar to yours. Cruising down the lake and the rpms would slightly drop and the exhaust would change pitch. Changed the plugs in the fall of 2015 and noticed the insulation where it meets the steel was rust stained. Not sure if the insulation was cracked and allowed the spark to jump or what. Been fine ever since.
 

Watty33

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May 30, 2015
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I disconnected the hour meter and also changed the spark plugs. Non were fouled but appeared to be original to the boat and have normal wear. Not seeing any sign of rust so I don't think there is water getting in the cylinders. Not seeing any sign of plug wires being an issue. Also don't hear a 'tick' like spark is arcing. I've rechecked electrical connections and grounds. Took it out this morning and the problem still exists after it ran for 5 to 10 minutes. Still has good power getting on plane and opens right up. Something is going on after it warms up while maintaining RPM.

Going to Lake Powell in 10 days for a week long houseboat trip and don't have much choice at this point but to throw parts at it. Will start with an ignition module and coil. Also considering a fuel pump to take with me but I really don't think it's a fuel issue. If it acts up at 4200rpm and I bump the throttle, it doesn't die out. It is responsive but will then start acting up again once rpm is maintained.

Is there any type of rev limiter on these motors that may be malfunctioning? Or a sensor that will kill the motor that is malfunctioning? I've tried shaking the ignition switch and kill switch while the issue is happening and it makes no difference.
 

alldodge

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If your tachometer is starting to short out it will kill the ignition. Disconnect the gray (I think) wire at the gauge
 
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