Volvo Penta 3.0GS engine missing mid throttle

[Badusername24]

I have a 1997 regal 1700LSR. WOT at 4200rpm with a 17 pitch prop (seems very low). It’s missing or “Bogging” between 2900-3400rpm. Above and below it runs perfectly smooth. Starts great and idles smooth at 1000rpm. Any ideas on where to start?

 

[Bondo]

Ayuh,..... Welcome Aboard,...... Sounds like a fuel delivery issue, probably the carb itself,.....
Yer Wot is pretty low, 'n yer idle is to high,.....

Wot should be at or near 4800 rpms, 'n idle should be 650/ 700 rpms, in gear, in the water,.....

 

[alldodge]

Look at your carb, probably needs a rebuild

 

[Badusername24]

Okay I’ll start with the carburetor. Probably throw new spark plugs as well. It was stored for 3 months before I got it with a half tank so it might have water in the gas… idk I’ll take a sample.

 

[alldodge]

Remove the fuel filter and see what the contents look like

 

[Badusername24]

Ayuh,..... Welcome Aboard,...... Sounds like a fuel delivery issue, probably the carb itself,.....
Yer Wot is pretty low, 'n yer idle is to high,.....

Wot should be at or near 4800 rpms, 'n idle should be 650/ 700 rpms, in gear, in the water,.....

It was at 1000rpm in neutral. Not sure what it was in gear if that makes a difference

 

[Badusername24]

I have a 1997 regal 1700LSR. WOT at 4200rpm with a 17 pitch prop (seems very low). It’s missing or “Bogging” between 2900-3400rpm. Above and below it runs perfectly smooth. Starts great and idles smooth at 1000rpm. Any ideas on where to start?

Update might be a small amount of oil in my spark plugs threads on the number 4 cylinder. Also took the cap off and found the carburetor filter was very clogged.

 

[alldodge]

Might have a valve stem seal leak on 4

The flame arrestor does look clogged. Use some diesel, carb cleaner and such would fix it right up

 

[Scott Danforth]

Any new to you boat, do ALL the maintenance the prior owner hasn't done

Clean you whole fuel system
Change all fluids
Pressure test gear box
Remove drive and inspect gimbal and joints
Replace your raw water impeller
Do a compression test

 

[QBhoy]

Almost certainly bad fuel. Ditch it, flush and replenish with new. Filter change and most likely need a carb clean now too. Should be good.
If you are keen…you could run it off a remote fuel tank to see what’s what. If the carb needs cleaned though…might not be too conclusive

 

[Badusername24]

Almost certainly bad fuel. Ditch it, flush and replenish with new. Filter change and most likely need a carb clean now too. Should be good.
If you are keen…you could run it off a remote fuel tank to see what’s what. If the carb needs cleaned though…might not be too conclusive

Yeah it was sitting for a bit with a half tank. I stupidly filled it up with full gas and put a bottle of stable in it. Didn’t wanna drain 30 gallons of gas but I might have to.

 

[QBhoy]

Yeah it was sitting for a bit with a half tank. I stupidly filled it up with full gas and put a bottle of stable in it. Didn’t wanna drain 30 gallons of gas but I might have to.

Haha. Been there before. I get your thinking. The older I got and the more Scottish (hugely variable temperature and humidity from one day to the next, over winter) winters gone by with fuel left in the tank…the more I learned that putting fresh fuel on top of bad or compromised fuel…just means you have more bad fuel than you started with.

 

[Scott06]

Yeah it was sitting for a bit with a half tank. I stupidly filled it up with full gas and put a bottle of stable in it. Didn’t wanna drain 30 gallons of gas but I might have to.

Looking at your plugs and filthy flame arrestor, clean the flame arrestor and try new plugs in it. Had a similar situation on my jet ski a few years back. Flame arrestor was plugged, ran fine on trailer , no power under load. Cleaned the flame arrestor, put new plugs in and ran fine. Was enough of a clogging in flame arrestor to act like the choke was on and foul the plugs.

you may have a fuel issue but take the fuel line off carb, put it in a container and pump some fuel into it while cranking. Let the fuel sit see what looks like or if moisture settles out.