Volvo Penta AQ200D V8 gasoline no reving higher than 3200 rpm

[Izy]

hello to all, I have a twin volvo penta aq200d petrol engines in my old Fairline Corniche 31, both engine runs fine and are well maintained, the issue that I am finding lately is that one of the engines don't rev higher than 3200 under load, while the other goes up to 4500.
The thing is that when in neutral, it does rev up, but not when the gear is on. Plugs are new, cabling of them too, petrol pumps runs well, .. not sure where to look for, thanks in advance for some good tips, cheers !

 

[Tranona]

First thing to look for is fouled propeller putting extra load on the engine.

 

[Izy]

First thing to look for is fouled propeller putting extra load on the engine.

hi, props are in good shape and works normally. thanks.

 

[PCUK]

Have you tried revving directly from the throttle lever on the carb/s in case the cable or control is faulty?

 

[Izy]

Have you tried revving directly from the throttle lever on the carb/s in case the cable or control is faulty?

not during load in the sea, but when in Neutral it does go up to max revolution without any problem, so that should somehow answer the question on the cable potential fault

 

[Freebee]

Revving in neutral is not the same as underload..underload requires more fuel..could be a fuel problem blocked filter, faulty pump??

 

[Izy]

have used chat GPT for that revving question, impressed with the load of info, pasting it here for other viewers :

If your Volvo Penta AQ200 marine engine is not revving up higher than 3200 RPM when in gear but can achieve higher RPMs when in neutral, several factors could be contributing to this issue. Here are some common causes and potential solutions:

### 1. **Propeller Issues**
- **Incorrect Propeller Size or Pitch**: If the propeller is too large or has too much pitch, it can cause the engine to struggle to reach higher RPMs. Ensure you have the correct propeller size and pitch for your engine and boat.
- **Damaged Propeller**: A damaged or bent propeller can also cause performance issues. Inspect the propeller for any signs of damage and replace it if necessary.

### 2. **Fuel System Problems**
- **Fuel Flow Restriction**: A clogged fuel filter, fuel lines, or fuel tank vent can restrict fuel flow to the engine, preventing it from reaching higher RPMs. Check and replace the fuel filter and ensure there are no blockages in the fuel lines or tank vent.
- **Carburetor Issues**: If your engine is carbureted, the carburetor might need adjustment or cleaning. Deposits in the carburetor can restrict fuel flow and affect performance.

### 3. **Ignition System Issues**
- **Spark Plugs**: Worn or fouled spark plugs can cause the engine to run poorly. Check and replace the spark plugs if necessary.
- **Ignition Timing**: Incorrect ignition timing can affect engine performance. Check the ignition timing and adjust it according to the manufacturer's specifications.
- **Distributor and Ignition Coils**: Ensure that the distributor and ignition coils are functioning properly and delivering a strong spark to the spark plugs.

### 4. **Engine Load and Condition**
- **Overloading**: If the boat is overloaded with weight, it can prevent the engine from reaching higher RPMs. Ensure the boat is not carrying excessive weight.
- **Engine Compression**: Low compression in one or more cylinders can cause performance issues. Perform a compression test to check the condition of the engine's cylinders.

### 5. **Exhaust System Restrictions**
- **Exhaust Blockages**: Blockages or restrictions in the exhaust system can cause back pressure, affecting engine performance. Inspect the exhaust system for any blockages or restrictions.

### 6. **Throttle and Control Cables**
- **Throttle Cable Adjustment**: Ensure the throttle cable is properly adjusted and allows the engine to reach full throttle when in gear.
- **Control Mechanism Issues**: Check for any issues with the control mechanism that might be preventing the throttle from opening fully when in gear.

### 7. **Water Intake and Cooling System**
- **Cooling System Issues**: Overheating can cause the engine to go into a protective mode, limiting RPMs. Ensure the cooling system is functioning properly and the water intake is not blocked.

### Troubleshooting Steps:
1. Inspect the propeller for size, pitch, and damage.
2. Check and replace fuel filters, inspect fuel lines, and clean the carburetor if applicable.
3. Check and replace spark plugs, and ensure proper ignition timing.
4. Perform a compression test on the engine.
5. Inspect the exhaust system for blockages.
6. Adjust the throttle cable and inspect control mechanisms.
7. Ensure the cooling system is functioning and there are no blockages in the water intake.

By systematically checking these components, you can narrow down the cause of your engine's performance issue and take appropriate corrective action.

 

[vyv_cox]

Fuel filter would be my first check. I have twice had exactly your experience with diesel. Not sure it would be the same with petrol as their function is very different but my philosophy is always to try the easy things first.
Are these carburettor or injection? Float level should be a clue if the former.

 

[Izy]

Fuel filter would be my first check. I have twice had exactly your experience with diesel. Not sure it would be the same with petrol as their function is very different but my philosophy is always to try the easy things first.
Are these carburettor or injection? Float level should be a clue if the former.

Carburator based, and was checked, working normally, this is keeping head busy, thanks for the hint