Reply
 
Thread Tools Search this Thread
 
Old 15 September 2009, 03:00   #11
Member
 
Country: UK - N Ireland
Town: Cushendall
Boat name: JanJack /
Make: RedbayBoats / Brig
Length: 8m +
Engine: Yanmar 300 / etec 50
Join Date: Mar 2008
Posts: 81
I've just realized I forgot to mention something.

Last season we would occasionally have an error light coming up on the dash, which said "boost", which I now after a little googling I think meant that the boost pressure was too high.

We asked Redbay about this, but as they mainly deal in yamaha's there couldn't really help us except to say it should be OK to run it, which we did and the light stopped appearing. Whether this was due to the problem fixing itself or the bulb in the error light going I'm not sure.

Does this perhaps point towards the turbo, possibly the wastegate if it's talking about pressures?
__________________

__________________
chorscroft is offline   Reply With Quote
Old 15 September 2009, 03:24   #12
Member
 
chewy's Avatar
 
Country: UK - England
Town: Up Norf
Make: Avon SR4,Tremlett 23
Length: 4m +
Engine: Yam 55, Volvo 200
Join Date: Apr 2007
Posts: 5,217
Boost, could be high or low boost pressure and does relate to your turbo. The higher the boost the faster you go... until you bend the rods!
__________________

__________________
chewy is offline   Reply With Quote
Old 15 September 2009, 03:26   #13
Member
 
Leapy's Avatar
 
Country: UK - England
Town: Sheepy Parva
Boat name: Sadly Sold
Length: no boat
Join Date: Sep 2008
Posts: 1,728
Quote:
Originally Posted by chorscroft View Post
I've been having this problem for ages now and thought I'd describe it here and see if anyone can help.

The boat is a Redbay Stormforce 8.4m wrap-around and the engine a Yanmar 6lp-stze 300hp with a Bravo 3 Leg.

The problem I'm having with it is the acceleration is painfully slow and the engine seems to get bogged down within the mid rev range.

What seems to happen is when you first push the throttle forward there's a rapid increase in speed up till about 1500 Revs. At this point the Revs increase very slowly as the boat comes onto the plane and up until about 2500 Revs and then again it accelerates rapidly from 2500 Revs up till about 3700 at WOT.

I'm fairly sure the problem isn't the boats weighting, and I assume the prop's are fine as it is within the recommended rev range at WOT.

I'm thinking the problem is something to do with the engine itself.
Does anyone have any ideas/suggestions etc of what to try or what to check?

Cheers

Conor
When you say the problem has been "for ages" it suggests that it wasn't like that earlier so my comments are based on it was right once, but now it's gone pear shaped.

If that's the case, it's difficult to think it's anything to do with the prop unless you've replaced it and the problem is coincidental with that.

If the engine produces the same-old maximum power it's difficult to think it's an engine mechanical problem.

If, after getting out of the hole, you've got the same max speed - and therefore maximum power - then the turbo is clearly working at least in part.

If you can achieve maximum power and maximum speed that suggests you're achieving maximum fuel flow so why would it be 'restricted' at mid-range? Blockages and restrictions generally restrict flow at all flow rates, not just at mid-range flows.

This brings me back to the turbo or its control mechanism...do you know at what rpm the turbo did or should start to deliver? Typically, this should be around 1200rpm(ish). If the onset of boost is delayed, for whatever reason, then this might explain the smart get-away (by sheer engine cubic inches), lethargy in the mid-range where boost is not forthcoming, followed by restored performance when the turbo belatedly kicks in.

I wonder if there a control system fault in the turbo mechanism? Is it electronic or mechanical control? If the latter, try and figure out what the mechanism is and does all appear connected and correct? If it's electronic control I fear it's a dealer visit.
__________________
Leapy is offline   Reply With Quote
Old 15 September 2009, 03:59   #14
Member
 
Country: UK - Wales
Town: Here
Boat name: doggypaddle
Make: Avon 5.4 Searider
Length: 5m +
Engine: yamaha 80
Join Date: Jul 2007
Posts: 1,107
does sound like a sticky wastegate. remove the linkage from the actuator and see if the flap is free. if not plus gas and wiggle it until all the corrosion and carbon is washed out of the spindle bush and its free again.
I occasionally get the same problem on the landrover, exactly the same symptoms, no loss of ultimate power but all the lovely 1200 rpm grunt vanishes!
I think the overboost light may be a clue its been sticking shut, mine used to do this and when it eventually overboosted enough to open it would stay open!
__________________
I am usually not as green as i am cabbage looking.
doggypaddle is offline   Reply With Quote
Old 15 September 2009, 05:17   #15
Member
 
Country: UK - N Ireland
Town: Cushendall
Boat name: JanJack /
Make: RedbayBoats / Brig
Length: 8m +
Engine: Yanmar 300 / etec 50
Join Date: Mar 2008
Posts: 81
When I say ages, what I really mean is as long as I can remember. It used to be my dad that would always have driven and sorted out maintenance (evidently not very well ).*

I also think that the engine isn't producing maximum power as I can remember a few years back the boat would easily do 40+ knots at WOT, whereas now it only manages 37-38 knots ish.*

How do I find out whether or not the turbo is mechanically or electronically controlled. Do yanmar keep archives of this info along with data about when the turbo should kick in? (*6lp-stze )

Also were abouts on the engine would I find the linkage and actuator to clean?

Cheers

Conor
__________________
chorscroft is offline   Reply With Quote
Old 15 September 2009, 05:30   #16
Member
 
Country: New Zealand
Town: Auckland
Boat name: Nirvana
Make: Zodiac
Length: 3m +
Engine: Yamaha
Join Date: Sep 2009
Posts: 2
We had a similar problem with a 12 Litre Volvo D12 turbo. Acceleration always slowed through a fixed rev range and was good below and above as you describe. After all sorts of tests on fuel filters, air filters, turbo etc turned out to be a faulty sensor on the turbo which was pulling back the fuel flow through that rev range. New sensor and shes been like new ever since
__________________
Cruiser is offline   Reply With Quote
Old 15 September 2009, 05:30   #17
Member
 
Country: UK - Wales
Town: Here
Boat name: doggypaddle
Make: Avon 5.4 Searider
Length: 5m +
Engine: yamaha 80
Join Date: Jul 2007
Posts: 1,107
Not wishing to be funny, but if you really dont know what or where the wastegate is, and the way it works I would get a good marine diesel engineer to have a look at it. starting with an oil and filters change, then checking fuel compensator and wastegate linkages, and fitting a boost gauge and checking boost pressure vs engine rpm.
Is a chicken and egg situation with this, if your fuelling is not correct then you wont generate the boost, and conversley if you aint got boost then it won't fuel up correctly.
I wouldnt fiddle with pump settings or anything else until everything else is ruled out. thats one advantage and disadvantage with a turbo diesel, one turn of the wrong screw on the pump and you may gain masses of extra power, over do it or get it wrong and you will have a sump full of pistons.
in short if you dont know about turbo diesels leave it to someone who does.....it may be much cheaper in the long run
__________________
I am usually not as green as i am cabbage looking.
doggypaddle is offline   Reply With Quote
Old 15 September 2009, 06:07   #18
Member
 
Leapy's Avatar
 
Country: UK - England
Town: Sheepy Parva
Boat name: Sadly Sold
Length: no boat
Join Date: Sep 2008
Posts: 1,728
Quote:
Originally Posted by doggypaddle View Post
...in short if you dont know about turbo diesels leave it to someone who does...
__________________
Leapy is offline   Reply With Quote
Old 15 September 2009, 09:51   #19
nik
Member
 
Country: UK - England
Town: east cowes
Make: academic
Length: no boat
Engine: fresh air
MMSI: N/A
Join Date: Sep 2003
Posts: 540
If there is lots of black smoke it could be a sign of blocked air filters.
I am pretty sure yanmars use mechanical fuel injection.
__________________
nik is offline   Reply With Quote
Old 15 September 2009, 11:19   #20
Member
 
Country: UK - Wales
Town: Here
Boat name: doggypaddle
Make: Avon 5.4 Searider
Length: 5m +
Engine: yamaha 80
Join Date: Jul 2007
Posts: 1,107
which is why i said he should get it serviced, though to be honest its unlikely, theres not usually much dust in that enviroment.
could be a blocked exhaust though. I think it was Gmacs pac22 that was down on power, and suddenly regained it when the exhaust flexi exploded in a shower of water steam and soot
__________________

__________________
I am usually not as green as i am cabbage looking.
doggypaddle is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 04:43.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.