Yamaha 421 boost issues?

[RBJT]

Hi guys.

So my turbo failed (lost a exhaust blade due to carbon build up). I have had it reconditioned from universal turbos, but now I have significant turbo howl and a lot less power.

With a full load the boat has to be WOT throttle for a good 15 seconds before the turbo kicks in and she is gets up on the plane.

I get the same revs and speed at WOT. Just seems to be lack of power to get out the hole.

Turbo was sent back and it’s confirmed all is correct now.

The noise from turbo is so much louder than before

Next thing I will look at intercooler.

Anyone have any advice or similar issues?

Boat is Redbay 8.4.

Cheers.

[RAS666]

Did you recover the missing blade from the rest of the exhaust system?

[RBJT]

Originally Posted by RAS666

Did you recover the missing blade from the rest of the exhaust system?

No. Surely it will be out the exhaust and in the Clyde now?

[beamishken]

Is it the engine with the pressure operated boost control on the back of the intercooler or the straight through one? If it has the control then it may not be operating stifling the boost. The other thing to check is fit a pressure guage into the inlet manifold to measure the boost

[RBJT]

Originally Posted by beamishken

Is it the engine with the pressure operated boost control on the back of the intercooler or the straight through one? If it has the control then it may not be operating stifling the boost. The other thing to check is fit a pressure guage into the inlet manifold to measure the boost

Hi ken.

I think it’s the later model with the straight through set up.

Will start stripping the intercooler tonight to see how that looks.

[beamishken]

Theres likely a boost pressure compensator pipe goes to the pump on that one, be worth checking the pipe is clear if it has it cant remember where it is but with no boost pressure regulator or waste gate there must be something tells the pump to fuel up when the boost comes in

[RBJT]

Originally Posted by beamishken

Theres likely a boost pressure compensator pipe goes to the pump on that one, be worth checking the pipe is clear if it has it cant remember where it is but with no boost pressure regulator or waste gate there must be something tells the pump to fuel up when the boost comes in

Hi mate.
IC all clear, but cleaned anyway.
The pipe your talking about is it a wee rubber one that goes from the top of pump to the manifold? If so all clear and in tact.

I am lost.

Now going to borrow a turbo from a mate and try that to see if the new (remanufactured) turbo is not correct.

Any other ideas much appreciated.

[Gareth231]

Have you tried fitting a boost pressure gauge to the inlet manifold? And checking you boost pressure..

Maybe you have a boost pressure leak.. Have you checked all the boost hoses?