volvo 4.3 running issues need advice

[enforcer30]

This is what I have going on. 96 volvo 4.3 SX drive. It runs great no miss no hesitation starts fine all guages normal , but it will not pull over 4,000 rpm. It used to pull 4,700 rpm. Prop/skeg is fine. I have tried cap/rotor, ignition module, new fuel filter, new fuel pump, used a external fuel tank to eliminate a problem with the anti siphon and check ball, gone through the carb, the plugs look good, I have no arking at the plug wires.
I am at a loss and have no idea what to check next. Plugged exhaust???? Any ideas or suggestions would be great.

Thank you, Barry Feltmann

 

[Haut Medoc]

Re: volvo 4.3 running issues need advice

When was the last time the wires were changed?.....
Was it a sudden, noticeable drop off?.....
Welcome to iboats, btw.....​

 

[mvn]

Re: volvo 4.3 running issues need advice

Throttle cable??

 

[enforcer30]

Re: volvo 4.3 running issues need advice

I am not certain how old the plug wires are, but I had no arking. However I plan to replace them. I don't think thats my issue but it will be worth a shot. According to my customer the boat overheated he brought it in to a different shop and it came back this way. P.S. I also did a comp. test 175-180 all cyl.
Thank you This is a good forum alot of information and seemingly good people.

Yes I did also varify full throttle from the shifter to the butterflies.
Thank you for your imput.

 

[bruceb58]

Re: volvo 4.3 running issues need advice

Maybe the exhaust flappers got cooked and are detatched and sitting in the bottom of the exhaust Y.

Probably also a good idea to check the compression.

 

[enforcer30]

Re: volvo 4.3 running issues need advice

Thats kinda the direction I am thinking. Is it common? It just seems like a odd failure. I assume I have to pull the drive unit to check. Would the exhaust flap give any other symptoms? I can say that the port exhaust riser is much hotter than the starboard side.
Thank you again for the response.

 

[bruceb58]

Re: volvo 4.3 running issues need advice

Thats kinda the direction I am thinking. Is it common? It just seems like a odd failure. I assume I have to pull the drive unit to check. Would the exhaust flap give any other symptoms? I can say that the port exhaust riser is much hotter than the starboard side.
Thank you again for the response.

On Volvos, the port riser is always warmer by 10 degrees or so. That is because of the water flow out of the thermostat housing.

As far as the flapper is concernerned, could view from either side.

 

[enforcer30]

Re: volvo 4.3 running issues need advice

Thank you for that information. That will save me some time.
A dumb question: Could this be a case of timing not advancing (I meen the fact that it only pulls 4,000 RPM. I also noted that the ignition module is only using one of its two plugins. What actually advances the igniton.

 

[bruceb58]

Re: volvo 4.3 running issues need advice

It's possible but I doubt it.

Very easy to check with a timing light to verify it is advancing. You have a manual? The specs for the timing are in there.

The other plug is where you plug in the shunt to allow the ignition to be put into base timing mode when setting the timing.

 

[enforcer30]

Re: volvo 4.3 running issues need advice

Alright guys this is what I found. I pulled the drive off and inside the boat (looking through the exhaust bellows) there is a large piece of rubber i.e. the flap about the size oa a really big potato chip.
Is there only one flap or two? I assume this was my problem.
Thanks again guys.

 

[enforcer30]

Re: volvo 4.3 running issues need advice

Guys I answered my own question. Yes there are 2 I took the other one out as it was ready to break off also.
Thank you all for the help. Once it is all back together I hope I have all my RPMs back. Thanks again, Barry

 

[enforcer30]

Re: volvo 4.3 running issues need advice

Well I did the repair went to the lake did NOT fix it. I still am only getting 4,000 RPM 4,200 over trimming. What else is left???? I can get 5K with no load. I am confused now. Any other ideas out there. I know this post is getting old I appologise.

 

[Apocalypso]

Re: volvo 4.3 running issues need advice

I had a similar situation with my 96 Four Winns 4.3GL several years ago. The engine ran fine until I tried to open it up and then would only reach about 3900 rpm (WOT 4600 previously). I asked the mechanic at the marina and he went for a ride with me to check the problem. With the engine running he removed the spark arrester. Then he told me to run up to full speed. As before it would only reach 3900 rpm, then he closed the choke butterfly slighly and the engine ran all the way to 4600 rpm. The problem was the power vale in the Holley 2bbl carb. I rebuilt the carb and all was good. Now I perform a rebuild on the carb about every three years. Been fine ever since.
HTH,
Jim

 

[enforcer30]

Re: volvo 4.3 running issues need advice

Thanks Jim I will give that a shot

 

[Don S]

Re: volvo 4.3 running issues need advice

I guess I missed your post the first time, here is what I normally post on these type posts, (and there are a lot of them)

List of possible causes of low WOT.

Engine Won't Reach Operating RPM. Check

• Fuel condition. Type and Octane possibly old fuel
• Propeller pitch or diameter, damaged blades
• Restricted fuel pickup tube or anti siphon valve Fuel System Test
• Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
• Marine growth on hull and outdrive
• Wrong gear ratio in outdrive
• Restricted carburetor air intake (clogged flame arrestor)
• Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
• Poor cylinder compression Compression Test
• Carburetor defective, or wrong type.
• Fuel pump pressure and vacuum
• Boat overloaded, improperly loaded, or improperly trimmed.
• Engine Overheating
• Engine timing and ignition system operation (Full tuneup done recently)
• Remote control cables and linkage for proper travel to open throttle plates fully.