Volvo Penta Tamd 41 Turbo boost won't work.

[Armeria]

Hi, This is my first post so I appreciate your input.
I had a blown piston on one of my engines and had the engine rebuilt. The mechanic took a year to do it and probably should not have taken it on. Now it's back in the water, everything on both engines checks out well but neither engine will reach past 2200 rpm and the turbo boost kicks in at 2700. Nothing has changed since the engine failure except for sitting for a year. The fuel pumps are calibrated, injectors tested, the turbos spin just fine and there is no movement in the bearings, does anyone have any idea as to why this would be?

Thanks.

[jimbunyard]

How well does it start? Does it smoke or overheat? How does it idle? Have you tried to operate it without the control; i.e. by hand at the engine with the cable disconnected?

The turbo should start making noticable boost at around 2000 rpm, and boost should continue building fairly linearly until max rpm of 3900. Unless there is a physical problem with the turbo, bad bearings, insufficient oil supply or damaged wheels, boost should be directly proportional to engine speed.

I'd guess something else is limiting engine speed, it could be something as simple as clogged filters or as difficult as a mistimed gear train.

[Armeria]

Thank you for responding so quickly. As for as your questions, it starts well, there is white a significant amount of white smoke from the rebuild when starting but lessons after five minutes. It idles just fine and doesn't overheat.
Yes, we have tried the throttles on the engines only but not with the cable disconnected however there is full travel.
You could be right, maybe the filters have wasp nests in them! we'll try that next as the boat was on land for the whole year. Thanks again for your input, I will post our findings when we have them.

[DougR]

A couple of things you might check....
- If your engines are early Tamd41A engines they were originally equipped with a butterfly valve in the exhaust elbow. The A version engines had a rather low compression ratio and they would white smoke at idle, so the valve was used to increase back pressure which caused more combustion heat and lowered the smoke level. The valve was controlled by a solenoid, and the solenoid was controlled by a micro switch connected to the throttle linkage on the injection pump. At idle the valve was shut, but as the throttle was advanced, the throttle lever activated the switch which energized the solenoid and opened the butterfly valve. Make sure the system is working or the back pressure will restrict performance. Later versions had higher compression ratios and this system was abandoned.

- All 41 series engines used Bosch VE type injection pumps and they were equipped with aneroid diaphragms or so called smoke limiters. This is a circular diaphragm in a housing on the top of the inj. pump. The chamber above the diaphragm is connected to the inlet manifold by a small hose, and this hose feeds boost pressure from the manifold into the chamber. There is a linkage from the bottom of the diaphragm into the pump, and if the boost pressure doesn’t push the diaphragm down, the injection pump will never deliver full fuel to the injectors. Make sure the hose and banjo bolts are open and able to flow air to the inj. pump.

[Armeria]

Thank you Doug for your input, I have forwarded this message to my new mechanic to see what his thoughts are, this level is beyond my capabilities!