Bogging in relation to distributor

[MalibuMike]

I have had a bogging issue for close to two years. It seems to happen above 3000 RPM and can be random. I have done everything to the fuel system that would be related to bogging. New fuel lines, fuel pump, running on a spare tank, removal of anti siphon valve, change filters, and fuel pressure test that are in the normal range.

On my last trip out, it bogged multiple times above 3000 RPM on the way to the Channel Islands. On the return trip I swapped out the crab style distributor cap because it is a known problem with these engines. I did not have any bogging on the return trip and ran around 3200 RPM and then pushed it up to 4000 for the last couple miles.

It’s hard for me to imagine that these caps can literally go bad in 3 to 6 months just sitting at the dry storage. And the cap does not have any kind of gasket when it sits on top of the distributor so salt air certainly gets in there and does cause some corrosion.

Does anyone have experience with these caps needing to be changed multiple times a year even if you only run your boat 10 to 20 hours a year? And if there is some corrosion, which in my mind creates resistance, what is the correlation with bogging above a certain rpm? The type of bogging i experiences is where the RPMs will slowly start dropping and even if you give it more throttle, it will be nonresponsive, and it will back itself down practically to an idle. There’s no popping or sound that would indicate a lean condition. I’m just trying to understand how, or if, a distributor above a certain rpm, can actually be attributed to this kind of bogging.

I am getting ready to replace the entire intake manifold, and I will need to pull the distributor and can inspect it for wear.

And I’m going to take a guess at one thing, but when the distributor is spinning at a higher revolutions per minute, which means somebody’s pushing on the throttle, wanting more fuel and air into the cylinders, is there something within the distributor that is telling the spark to get more powerful and if there’s corrosion there, you kind of reach a threshold of not having a good enough spark above certain RPMs?

The block is from 2007 and has approximately 700 hours on it.

 

[kenny nunez]

Have you ever tried just replacing the rotor when it starts to lose power?
Rotors will go to ground when hot and the symptom you are describing is how a marine engine acts when that happens.
Do you have electronic or breaker point ignition?

 

[MalibuMike]

I’m really not sure how to answer that, but it is the crab style cap sitting on this distributor

If I did need to order another one, would it be an automotive one or a special marine one?

 

[MalibuMike]

Have you ever tried just replacing the rotor when it starts to lose power?
Rotors will go to ground when hot and the symptom you are describing is how a marine engine acts when that happens.
Do you have electronic or breaker point ignition?

Just posted below. And to clarify if I back off the throttle from the bogging and let the boat just idle for 20 seconds it can ramp right back up to 3000 RPM I might not bog for five minutes or 15 minutes.

 

[kenny nunez]

Just try replacing the rotor. Stay with the original style cap.

 

[ESGWheel]

Malibu
Please provide your engine model and other pertinent boat info.
The picture looks like ‘crab cap’ type of distributor and they do not have a gasket to seal the cap. In fact, these dist. are purposely vented and compliant with the J1171 standard. See this post (link) for some info on that and where the vents are.
If these vents are blocked it’s possible that moisture build up under the cap is causing premature failure. Check them by pulling the rotor and using a good light source under the dist.
There is not a ramp up the spark due to higher RPM.
Replacing the rotor and cap as a set is best practice.
You may also have a failing / weak coil and the new cap with its less resistance helps it just enough to have no issues when new.

Why are you pulling the intake manifold? And need to be careful of the clocking relationship of the dist. and cam....

 

[MalibuMike]

Malibu
Please provide your engine model and other pertinent boat info.
The picture looks like ‘crab cap’ type of distributor and they do not have a gasket to seal the cap. In fact, these dist. are purposely vented and compliant with the J1171 standard. See this post (link) for some info on that and where the vents are.
If these vents are blocked it’s possible that moisture build up under the cap is causing premature failure. Check them by pulling the rotor and using a good light source under the dist.
There is not a ramp up the spark due to higher RPM.
Replacing the rotor and cap as a set is best practice.
You may also have a failing / weak coil and the new cap with its less resistance helps it just enough to have no issues when new.

Why are you pulling the intake manifold? And need to be careful of the clocking relationship of the dist. and cam....

1997 Parker 2520 with a Gi-g 5.7
New block installed 2007 based on the casting numbers. It is the crab style cap. 700 hours. Low pressure, idle psi, and high pressure taken on the rail are at spec. And at 3000 RPM the fuel pressure remains within spec.

I found an incredible deal on an intake manifold, a brand new Volvo Penta still in the box with the throttle body , and all the sensors and fuel injectors for $600. I think list was $2500. My intake manifold has a lot of rust and corrosion and the bolt holes are really starting to look rough and even when I tried to change the IAC sensor one of the screw heads snapped off so everything’s just getting a bit rusty. Especially around the bolt holes that bolts the manifold to the block, they are really starting to show flaking rust, but I do not believe I have any intake manifold leaks yet.

I also swapped out the coil with another one, a used one from the lake boat, but didn’t change the bogging.

So the only things I’m really left to consider are a fuel pump that is malfunctioning, but it was replaced a few years ago with an OEM Volvo penta, so there are no paint flake issues, unless, the company that installed it grabbed a really old one off the shelves and maybe I need to inspect the screens on the high and low pressure. But again I never hear any whine that would indicate restriction.

Or something electrical is malfunctioning, maybe the distributor cap and rotor, where it almost feels like some of the cylinders are deactivating.

 

[Scott Danforth]

so you want to spend $600 on a $400 GM manifold that you could just spend $5 on paint after you wire brush the rust? its your beer money

cleaning and painting along with fluid film or boeshield should be considered normal maintenance on a salt water boat.

swap the cap AND the rotor. yes, the crab caps go back fairly quickly, not 3-6 months, however about every few years its an issue with how they are made, and that they short out internally because there is very little plastic between the brass connectors as they cross each other. this causes various cylinders to fire when they shouldnt. the salt air and corrosion doesnt help. corrosion on the contacts also causes prolonged arcing, which causes arc tracing which also fires multiple cylinders when it shouldnt.

in your case, changing the cap disturbed the rotor a bit. that is most likely why you noticed an improvement.

regarding a gasket under the cap, a thin layer of spark plug boot grease (dielectric grease) around the lip of the distributor will keep it sealed and prevent corrosion

the distributor is a GM unit. yours just needs to be pulled apart, soaked in oxalic acid (or bead blasted) to remove the corrosion in the picture and have new bushings installed and put back together with a bit of paint on the raw aluminum. If you want to buy a new one, feel free. its your beer money

 

[MalibuMike]

so you want to spend $600 on a $400 GM manifold that you could just spend $5 on paint after you wire brush the rust? its your beer money

cleaning and painting along with fluid film or boeshield should be considered normal maintenance on a salt water boat.

swap the cap AND the rotor. yes, the crab caps go back fairly quickly, not 3-6 months, however about every few years its an issue with how they are made, and that they short out internally because there is very little plastic between the brass connectors as they cross each other. this causes various cylinders to fire when they shouldnt. the salt air and corrosion doesnt help. corrosion on the contacts also causes prolonged arcing, which causes arc tracing which also fires multiple cylinders when it shouldnt.

in your case, changing the cap disturbed the rotor a bit. that is most likely why you noticed an improvement.

regarding a gasket under the cap, a thin layer of spark plug boot grease (dielectric grease) around the lip of the distributor will keep it sealed and prevent corrosion

the distributor is a GM unit. yours just needs to be pulled apart, soaked in oxalic acid (or bead blasted) to remove the corrosion in the picture and have new bushings installed and put back together with a bit of paint on the raw aluminum. If you want to buy a new one, feel free. its your beer money

Thank you for the help. Ill try your suggestions. The boat was from the east coast then Texas and had some corrosion when I received it. I store it in dry storage ( an open lot here in CA) but close to the shore where there is heavy salt air from large surf.

The manifold I have shows some really bad rust around the hold down bolts and around the fuel injector holes. Not just surface rust, this is rust that is peeling away in lines like a pie crust that is drying out! For $600 Ill either keep the manifold for later use or sell it at a profit. Used clean ones go for $850 on eBay so I felt it was a good purchase. And if I ever use it, I can clean the old one and sell it. Plus this new manifold has new injectors, new fuel pressure regulator, and all new sensors.

Ill try to upload some pictures of the cap when I pulled it for reference of what my corrosion looks like after a few months of storage.

Volvo Penta Boat Intake Manifold 3861984 | Sterndrive

Boat part number 1089911 is a new intake manifold from Volvo Penta, part number 3861984 .

www.greatlakesskipper.com

 

[ESGWheel]

@Malibu, if your current manifold is that rusty, I would suspect the injector bores are also fairly rusted up and will cause a problem not just pulling injectors for maintenance but also being able to properly seal back up again without a lot of effort in the injector bore. The new one was a steal and I think you will be glad you swapped it out. I would swap it and sell the used one

@scott, I understood these distributors are vented vs. sealed. I know my 2005 5.0 GXi-E is vented albeit a plastic housing vs. the aluminum.
Yes/no?
Thanks.

 

[MalibuMike]

Cap Just sitting out for like 4 to 5 months. Is this enough to cause a bogging situation?

 

[ESGWheel]

pics of the rotor?

 

[MalibuMike]

pics of the rotor?

Boat is an hour away but will post soon. Should I switch over to a cap with brass?

so you want to spend $600 on a $400 GM manifold that you could just spend $5 on paint after you wire brush the rust? its your beer money

cleaning and painting along with fluid film or boeshield should be considered normal maintenance on a salt water boat.

swap the cap AND the rotor. yes, the crab caps go back fairly quickly, not 3-6 months, however about every few years its an issue with how they are made, and that they short out internally because there is very little plastic between the brass connectors as they cross each other. this causes various cylinders to fire when they shouldnt. the salt air and corrosion doesnt help. corrosion on the contacts also causes prolonged arcing, which causes arc tracing which also fires multiple cylinders when it shouldnt.

in your case, changing the cap disturbed the rotor a bit. that is most likely why you noticed an improvement.

regarding a gasket under the cap, a thin layer of spark plug boot grease (dielectric grease) around the lip of the distributor will keep it sealed and prevent corrosion

the distributor is a GM unit. yours just needs to be pulled apart, soaked in oxalic acid (or bead blasted) to remove the corrosion in the picture and have new bushings installed and put back together with a bit of paint on the raw aluminum. If you want to buy a new one, feel free. its your beer money

Here’s the type of rust that is starting to get on the bolts and why I thought it was a smart idea to pick up a very expensive part for such a low cost

 

[ESGWheel]

Should I switch over to a cap with brass?

Here’s the type of rust that is starting to get on the bolts and why I thought it was a smart idea to pick up a very expensive part for such a low cost

Yes on the brass, but i do not see that the product descriptions state whether or not aluminum or brass. The Sierra branded ones I get are brass in color and thus I assume brass.

Regarding the manifold: Wow, pie crust for sure.

 

[MalibuMike]

pics of the rotor?

 

[dubs283]

Just this past week had a twin crusader setup with 5.7 HVS ignitions with a stbd engine failure to run

Had summerized and lake tested with expected results. Customer took boat and returned in less than an hour complaing stbd engine died and couldn't restart.

Found spark from coil to cap, no spark from cap to plugs. Inspection yielded results similar in appearance to the pictures posted in this thread. Solution was new oem (Mercury) cap/rotor. Engine fired right up and ran without issue

Tried talking customer into full tune ups on both motors and when quoted price I swear he turned green. Caveat applied to not be surprised if port engine suffers same failure, ymmv

 

[MalibuMike]

Here’s a follow up. I change both the cap and rotor and for now the bogging seems to have disappeared. Around 75 miles today and for the first half stay right around 3100 RPMs and only return home bumped it up to 3300 RPMs. No bogging occurred at all today, this cabin rotor is made by NAPA in the product line is called Echlin. It carries a lifetime warranty, so I will likely start replacing these for free every six months.

 

[dubs283]

I will likely start replacing these for free every six months.

A distributor cap and rotor is/are maintenance items and likely will not be covered under a lifetime warranty

Worth a try but don't be surprised if you have to pay for new

 

[ESGWheel]

Malibu,
I have seen a post where the rotor plastic is too thin (according to the poster) and the rotor arced on the back side of the rotor. Any evidence of that? Else the rotor looks good (other than apparently not being brass).

 

[MalibuMike]

Have you ever tried just replacing the rotor when it starts to lose power?
Rotors will go to ground when hot and the symptom you are describing is how a marine engine acts when that happens.
Do you have electronic or breaker point ignition?

I switched out those cap and rotor and ran the boat for two straight hours at around 3200 RPMs and did not have any bogging. Because these cabin rotors come from Napa, they have a lifetime warranty and I’ll probably just swap them out every 3 to 4 months regardless of condition. It’s kind of a pain, but maybe it’s the best solution.
I could only achieve 4100 RPMs at maximum throttle. I have a 25 foot Parker they do a prop hour drive with F3 props. So my next thing to assess will be why I can’t achieve a higher RPM, which I think should easily be 4600 or more.

I’m trying to wrap my head around the bogging mechanism that you a tribute to the rotor going to ground. Because my type of bogging is a slowing of the RPM and lack of power, let’s say it goes from 3000 RPM to 1000 RPM over the course of 30 seconds, what exactly is happening with the spark in relation to the cylinders?