Volvo Penta bogging down

[carjockey]

Hi Everyone! This forum has been very helpful but I have yet to solve my own problem. So here goes the long story and I hope someone has an answer! I just purchased a 2000 Four Winns 234 funship with a 2007 Volvo Penta 5.0 OSi. I've had this boat out a handfull of times. It will start and idle just fine. When accelerating to WOT the boat planes out and runs just fine. After about a mile it will bog down and idle itself back to around 2500 rpms. The first few times it would do this at WOT but would run at 3000 rpm most of the day. Now it doesnt matter what speed, it bogs down after about a mile on the water. When it bogs down I can pull back to nuetral, wait literally a few minutes and go again without shutting the boat off or anything but it will continue to happen just the same way. I had the fuel cell replaced last week. This past weekend was when it got worse. Dont know if thats coincedence or not. When it bogs down you get like an emission or fuel type smell. This is very consistent. I can time within 100 yards of when its going to bog down the first time. Here is what has been done to correct it:

1) Replaced fuel water seperator- ran with no change

2) Replaced water temp sensor. Ran with sensor plugged in and unplugged. No change

3) Replaced fuel cell. Ran and same same problem only worse (They put in new anti syphoning valve)

4) Knocked check ball out of valve and ran with no change

5) Have tried running with both oil sensors unplugged- no change

6) Unplugged sensors on top of risers- ran with no change

This weekend while water testing we hit a large wake hard and boat died. First time its died. Fired right up and ran normal. With it on muffs later running was jiggling wires and the main plug on the back of the motor killed everything when jiggled a little. Took that off and cleaned. Will still kill the boat but you have to move it quite a bit. I dont see how this would affect my initial problem but wanted to mention it. A friend thought maybe a broken wire in that plug could be acting up when the motor heats up but I dont see how that would send the boat into EPM. Nor do I see how the problem could be this consistent. The only mechanic that has looked at it is the one that insisted I needed to spend a grand to replace the fuel pump.

Any ideas? I'm at my wits end here!

Oh yea, I forgot to mention that the boat is fuel injected.

 

[Fun Times]

Re: Volvo Penta bogging down

Hi there, Have you checked to see what the spark plugs look like? While the engine is very warm, you may want to do an cylinder compression test just to try and narrow down if it's an engine mechanical condition, EFI problem, fuel system problem.

Bear in mind that a partially clogged exhaust system can cause unusual running symptoms.

Also you will want to put a fuel pressure test gauge on to see what the fuel pressure is actually doing.

At some point your going to need to hook up an EFI scan tool to see what's going on. Either you can buy one or a marine tech should have one.

Doing an engine vacuum test helps narrow down a lot of theories.

Hope some of these ideals will help, Good luck.

 

[carjockey]

Re: Volvo Penta bogging down

Thanks! No I havent checked these things. I took to boat in last week for this problem. The mechanic said over the phone it was probably the fuel cell. I argued that those either work or they dont. This is predictable. I dropped it off and they checked it all out supposedly and still arrived at needing a thousand dollar fuel cell. So I was trying to run down as much as I could before having them look at again next week.

 

[robr229]

Re: Volvo Penta bogging down

Sometimes that is not always the case with the fuel cell they can still work but will not supply the prober fuel

 

[carjockey]

Re: Volvo Penta bogging down

So here it is!! I've thought from the beginning that it was heat or pressure related some way. 2 weeks ago the mechanic replaced the impeller (the previous owner said he had and it still looked ok) then discovered the thermostat was all rusted and not functioning (why do you need a thermostat on a boat?). He replaced those and ran it on the lake using a laser to check the heat. His laser showed ok but the boat still went into EPM. With the engine shut down and key off he unplugged the sensor and it ran without going into EPM. I hooked a manual guage up to it and ran it yesterday. At idle and under a load running low RPM its fine. Stays around 150. once I get up on plane it starts to heat up. Will climb to 200 after about a mile. Mechanic thinks theres something cracked and when the boat planes out its sucking air in and interupting the water flow. Does this make sense? This is a marina mechanic that works on houseboats with volvo engines. I'm assuming he knows what he's doing but it doesnt sound right to me.

 

[dypcdiver]

Re: Volvo Penta bogging down

Sounds to me that you are not getting enough raw water flow to the engine. You might just be pulling air through the raw water pump seal, or a lose hose connection to the outdrive, the shaped "O" ring on the drive to pivot housing, or lastly the seals between the upper and lower drive housings.
Get some clear PVC hose that can be fitted into the suction side of the raw water pump and to the output of the pump and check to see if you are pulling air, which will appear as bubbles in the water flow. If there are bubbles on the suction side then obviously you have a leak between the drive and pump, if you have bubbles only on the output then it is the seal in the pump.
There are plenty of posts even videos describing and showing this test method if you do a search on this forum.

 

[ericga]

Re: Volvo Penta bogging down

I would definitely inspect manifolds and risers for restriction in water passage.