99 Volvo Penta 5.0 bogging at 90%+ throttle

[thatchevyguy]

I'm having trouble with the engine bogging slightly at 90% or more throttle. If I stay at 90% or less throttle, it runs, and idles perfectly. This isn't a sharp stumble like an ignition problem, this is a slow progressive loss of acceleration.
I have read previous posts about issues with the paint from the fuel cells clogging the screens, and pumps making whining noise. The thing is that I have a different setup. I have a Low volume pump and a fuel separator mounted up front, and a vapor separator tank with High pressure pump mounted on top of it. The VST is mounted on the very rear of the engine. I have the VST removed and cleaned it and the screens on the HP pump. About 10% of the HP pump inlet screen was covered with a piece of oring. The oring was from a banjo fitting that's made into the inlet of the HP pump. Maybe it was catching air at the missing oring? It wasnt leaking fuel here.
It's all been put back together, and I plan on cleaning the screens on the LP pump in the morning. Maybe even change the anti siphon valve.
I have regularly changed the filter separator, and used ethanol free fuel. I have a few questions.

1: Am I on the right track?
2: What are going to be my options when I need replace this reservoir? Update to the new all in one style that mounts up front?

1999 Volvo Penta 5.0 GIPWTR
411615313
3868844

 

[Fun Times]

Hi there, welcome to iboats

Well hopefully you'll never have to replace the fuel reservoir system. Maybe you'll have a minor cleaning or rebuild at times but you really shouldn't have to switch systems.

Here's your parts catalog if needed, http://www.volvopentastore.com/Mari...on_id.617137712--store_id.366--view_id.765176

Since you seemed to have found something blocking the inlet system, then hopefully that will be your problem as it's pretty important to have a clean flow. There are many threads as to where debris was found at the fuel pumps screens causing similar running issues such as yours.

Should it continue to run bad then you'll want to connect a fuel pressure gauge both to the low and high pumps to see what your getting under load/during the problem.

Also it's sometimes helpful to temporarily connect a small external outboard fuel tank with an primer bulb in order to bypass the boats fuel tank to see if the engine will run 100% again. As an additional test, try adding a little extra pressure using the primer bulb while it's running bad.

When was the last tune up including distributor cap and rotor?

Hope it's an easy one to find, good luck.

 

[thatchevyguy]

I replaced the dist. cap, rotor, wires, and plugs last season. Just as maitenance.
I've got to keep her new. The problem hasn't gotten so bad that I couldn't live with it, but I'm trying to stay ahead of it. I wanted to address this now as I budget money every year for maintenance, and next year I am planning on a full upholstery job. So far this has been the perfect sized boat for what we do. I haven't even started researching the cost of the upholstery yet. Tthanks for the link and quick reply.

 

[Tail_Gunner]

That should give you something to work with one last thing to notice you need a solid vacum ....no leaks, Not marine stuff but it's really very simple... same principle's and he does well with it...sort of.... Your mefi use's 5volts as a base...note the dead spots on the tps. See page 20 for vacum reference's

https://drive.google.com/file/d/0B3w...Z2s/edit?pli=1