1998 Volvo/OMC - When shifting to forward, the motor stalls. It runs fine on muffs.

Bill4452

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1998 Volvo Penta 5.7 - model 57FCPBYC, serial number T01311023.
When starting and running the motor on muffs in the driveway, the engine runs ok. As soon as you put it in the water and shift to forward the motor stalls. It will restart and running it in neutral is not problem. I can rev the motor to 1500 rpm with no issue. The cylinder compression runs from 185 thru 174 on all eight of the cylinders. Checked and there is no water in the fuel/water separator filter. Marina had it for three weeks and couldn't figure it out. Have scheduled a second marina to look at it. New Plugs, wires and cap have been installed. IAC and TPS have been replaced.
 

Lou C

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Does it stall in reverse as well? Will it shift into gear without stalling when on land running on the water hose?
If it's suspected that the outdrive is locking up it could be removed, and water could be fed to the raw water pump to run the engine with the drive removed.
A dock line wrapped around a prop shaft can stall a 200 hp 4.3 at idle so it doesn't take much.
 

Bill4452

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Does it stall in reverse as well? Will it shift into gear without stalling when on land running on the water hose?
If it's suspected that the outdrive is locking up it could be removed, and water could be fed to the raw water pump to run the engine with the drive removed.
A dock line wrapped around a prop shaft can stall a 200 hp 4.3 at idle so it doesn't take much.
It didn't stall on land when running on hose and shifted to forward
. I didn't rev it to high (Maybe 1,000 rpm). I can check reverse tonight.
 

Lou C

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I'm wondering if you're getting water in the cyls when launching the boat....
 

Lou C

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Pull the spark plugs & see if water comes out the cyls
 

ESGWheel

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I'm wondering if you're getting water in the cyls when launching the boat....
Lou,
Not sure I understand about the water. OP can start the boat post launching and after stalling, able to restart and run it up in neutral. Thanks.
 

Lou C

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Something it putting an extra load on that engine once there’s water in the Y pipe. Water in the cyls can cause misfires and rough running also, perhaps back pressure is too high, did this engine have the flappers that Volvo later said to remove? If these work loose or melt from an overheat they can block the exhaust & cause high back pressure….
Remember on the water hose the y pipe is not totally full of water so back pressure isn’t as big an issue as when the boat is in the water and the Y pipe fills up with water.
PS a1998 probably had those flappers, by ‘99 Volvo was saying remove them in a TSB.
 
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Bill4452

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Something it putting an extra load on that engine once there’s water in the Y pipe. Water in the cyls can cause misfires and rough running also, perhaps back pressure is too high, did this engine have the flappers that Volvo later said to remove? If these work loose or melt from an overheat they can block the exhaust & cause high back pressure….
Remember on the water hose the y pipe is not totally full of water so back pressure isn’t as big an issue as when the boat is in the water and the Y pipe fills up with water.
PS a1998 probably had those flappers, by ‘99 Volvo was saying remove them in a TSB.
I bought the boat later in 2010 or so. I can't verify if the flappers have been changed. Is there a way for me to check or is that something a service tech needs to do?
 

Lou C

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Well it’s not a hard thing to check but it involves loosening the clamps that hold the rubber exhaust hoses to the elbows, 90* down pipes & Y pipe. Then you can remove the in 90* down pipes & see the top of the Y pipe if the flappers are there it will be obvious. If not but you see the rod they pivot on still in place they could have melted off due to a previous overheat. I had that happen on my Cobra (same design Volvo actually adapted OMCs transom mount for the SX) and I had to remove them in outdrive to get the melted bits out. If they were removed as per Volvos TSB the rods would have also been removed.
 

Bill4452

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Well it’s not a hard thing to check but it involves loosening the clamps that hold the rubber exhaust hoses to the elbows, 90* down pipes & Y pipe. Then you can remove the in 90* down pipes & see the top of the Y pipe if the flappers are there it will be obvious. If not but you see the rod they pivot on still in place they could have melted off due to a previous overheat. I had that happen on my Cobra (same design Volvo actually adapted OMCs transom mount for the SX) and I had to remove them in outdrive to get the melted bits out. If they were removed as per Volvos TSB the rods would have also been removed.
Thanks for the info. I'm currently looking for a tech to come and inspect them.
 

Lou C

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part number 42 are the exhaust flappers
in the pic below you can see the lower exhaust hose, the flapper is below that at the top of the Y pipe. this is my 4.3 V6 but the design of the V8 is similar
I always wondered about this Volvo TSB, removing them to me didn't seem like a great solution because water can rush up the Y pipe and hydrolock the engine
I know Volvo adapted the OMC design and this is part of the original Cobra design
I have them on my older Cobra and when I had a bad overheat, the engine would still run fine in the water but I had to pull the outdrive to get the bits of them out.
I'm trying to think of another reason why your engine stalls when putting it into fwd in the water but the only other thing I can think of is resistance in the drive unit, because in the water, the prop is pushing against the water which causes a lot of drag, whereas on land, no real drag prop spins freely.
What's the drive oil look like? Any water in the oil?
PS, you never answered my question, does it stall in reverse as well?
Exhaust install wiht headless bolts to line it all up.JPG
 
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Bill4452

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part number 42 are the exhaust flappers
in the pic below you can see the lower exhaust hose, the flapper is below that at the top of the Y pipe. this is my 4.3 V6 but the design of the V8 is similar
I always wondered about this Volvo TSB, removing them to me didn't seem like a great solution because water can rush up the Y pipe and hydrolock the engine
I know Volvo adapted the OMC design and this is part of the original Cobra design
I have them on my older Cobra and when I had a bad overheat, the engine would still run fine in the water but I had to pull the outdrive to get the bits of them out.
I'm trying to think of another reason why your engine stalls when putting it into fwd in the water but the only other thing I can think of is resistance in the drive unit, because in the water, the prop is pushing against the water which causes a lot of drag, whereas on land, no real drag prop spins freely.
What's the drive oil look like? Any water in the oil?
PS, you never answered my question, does it stall in reverse as well?
View attachment 409946
Sorry, Reverse in the water was ok at Idle speed just out of neutral. Did not try to give it the gas in reverse.
 

Lou C

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So shift to fwd stalls but rev ok? Make sure you tell the techs that….
 

cyclops222

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Just remember that a prop and exhaust in FOWARD are pushing SOLID water.
In REVERSE the prop is spinning in a MASSIVE CLOUD of exhaust fumes. NO hp is needed when boat is floating.
Ignition appears to be good.
I like the EXHAUST FLAPPERS stuck somewhere.
 

Lou C

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That would be the cheapest repair of all possible causes!
 

Bill4452

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I pulled the prop and there is no string wrapped around the shaft.
I tried taking the exhaust hoses and clamps off, but there was not enough of wiggle space to remove them. I didn't have an exhaust gasket to remove the exhaust elbow. I tried feeling for the flapper pin (Number 41 on diagram) but couldn't feel it on either side. I thought I would be able to at least feel that flapper pin from what the Diagram showed.
 
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