Yamaha ME421STI

philaustin · 26 December 2011, 12:24

I have a 8.2 metre Rib with a Yamaha ME421 STi inboard fitted. When the boat is loaded thee is a very significant "turbo" lag before the boat will plane. The engine can take five minutes to hit around 1900 RPM at which time the turbo kicks in and the boat takes off. Anyone had similar experiences?
I also need to obtain a service manual for same engine, any ideas?
Phil

biffer · 26 December 2011, 13:54

Sounds a heavy boat What revs do you get once it's going

sent from a remote device

Alan Priddy · 26 December 2011, 14:22

Common problem, adjust the turbo boost screw underneath the pump Alan P

AMac · 26 December 2011, 19:58

Also heard of problems with the turbo veins getting coated in soot/ oil residue and needing cleaned regular to let the turbo spin up quicker

Neville · 26 December 2011, 22:59

Phil,

There is also a pneumatic baffle (gate) which blocks off the turbo pressure when too high. This can stick slightly. You will find it (and the actuator) between the inlet manifold and the turbo. You can easily check that it is functioning ok visually and also by moving it with your finger to ensure it is fully open.

Good luck.

philaustin · 27 December 2011, 08:12

This is fantastic feedback, I am a new member and this is all great advice. The boat revs at around 3800 RMP which returns around 43 knots unloaded and 38 with four divers and twin sets.

Declanor · 27 December 2011, 08:46

I have a manual if you can find a at of copying it! Can find any online

kubcat · 27 December 2011, 09:25

Quote:

Originally Posted by Declanor

I have a manual if you can find a at of copying it! Can find any online

I have been looking everywhere for a manual and can't find one online. If I was closer I would come around and photocopy it myself.

biffer · 27 December 2011, 11:56

Quote:

Originally Posted by philaustin

This is fantastic feedback, I am a new member and this is all great advice. The boat revs at around 3800 RMP which returns around 43 knots unloaded and 38 with four divers and twin sets.

thats right on the button then, assuming it's always done it i'd have a look at Al's pump adjustment, i'm not sure the wastegate would bother the speed pickup but it would make the inlet manifold run hot, had that stick on the cummins engine we run

Roger Marr · 27 December 2011, 12:38

If its the rib I think it is you have a lovely boat, I know the guy who had it built.

willk · 27 December 2011, 14:48

Quote:

Originally Posted by philaustin

he boat revs at around 3800 RMP which returns around 43 knots unloaded and 38 with four divers and twin sets.

This sounds about right. As the guys say, there must be something up with the turbo.

You profile says Ferryboat. I reckon your boat is a very tasty looking Ferryman Boats wraparound open console. A good deal...

willk · 27 December 2011, 14:50

Quote:

Originally Posted by Roger Marr

I know the guy who had it built.

...and I know the guy who built it for him!

Clyde · 29 December 2011, 10:08

Phil, turbo sounds ok, that boat is stern heavy,try moving the weight forward, should make difference.

Andy Gee · 29 December 2011, 11:22

Phil,
I know the boat well and I have never know it to have any turbo lag, infact quite to opposite

.
When you say turbo lag do you mean that she is slow to get up to the speed when the turbo comes in (around 1900 if I remember correctly) or she is slow once the turbo starts to wind up (after @1900rpm)?

I would assume that you have checked the usual suspects i.e dirty bottom, Fuel/Air filters etc?

I might just know a man that has a full set of w/shop manuals etc for that unit including the drives on soft copy

Cheers
Andy

philaustin · 29 December 2011, 11:33

Roger,
It was William Macbeth, very nice chap and a cracking name.
I dive off it in Anglesey and it a fantastic boat. The hesitation is irritating and I need to get it fixed.

Roger Marr · 29 December 2011, 16:37

Quote:

Originally Posted by philaustin

Roger,
It was William Macbeth, very nice chap and a cracking name.
I dive off it in Anglesey and it a fantastic boat. The hesitation is irritating and I need to get it fixed.

The very man. Agreed it is a superb boat. Been out in some nice weather on her. A good dry boat.

Clyde · 04 May 2012, 14:19

Phil, how did you get on with the boat?. Drop me a line to let me know how you got on. Willie.