Mercruise 3.6D down on power

Converging

Converging

Well-Known Member
Joined
16 Jul 2009
Messages
182
Location
Warwickshire Moored Cardiff
Visit site
Hi Guys,

Yes, its me AGAIN!!!

1996 Sealine Statesman 330 - Mercruiser 3.6D

Changed head gasket - which cured oil leak.
Did compression test - all ok
Had injectors tested and all ok.
Adjusted valve clearances

AND

The engine is still 500rpm behind its partner.

Filters were changed July last year.
Diesel hoses were renewed last year

Engine revs fully when not under load.
Props look identical
Throttle cables checked to check full throttle is being acheived

What,s next before I drill holes in the bottom and sink it!!!!!!!!!!!!!!!!!!!!!!!!!!
 
Spooky!!

I had exactly the same issue with a pair of GM V8 Diesels. Did all the things you did which is spooky. In the end sent the fuel pump away for testing and needed a new pump body as there was some internal pump wear thus the pressure towards the upper rev range was weak. It was a such a pain to diagnose as just like yours it would rev up no problem but when under load was gutless and wouldnt rev out. the pump overhaul fixed the problem and the engine got its go back:)

Maybe worth sending yours away for testing if you have done everything else.

Its either going to be fuel, air or compression to drop 500 revs.

I also did the lift pump and all the little tiny filters before reluctantly sending the pump off.

Is it electronic or mechanical on those engines?

PM if you wish to have a chat as this took 6 months of my life to sort out with loads of investigations in to this that and the other!!

Good luck
 
Sounds like fuel starvation , do you get any black smoke from that engine, have you examined the turbo for damaged blades and worn blades on the exhaust side as its pretty close to the raw water and can corrode to turbine blades, so not spinning up and giving the desired amount of boost.

Is the boost pipe from the inlet manifold ok.

Have you stripped the lift pump.

Open both the fuel taps on the crossover just incase there is a restriction from the tank.

Test the engines with a hand held rev counter.
 
Hi Paul,

No Black Smoke

Turbo blades are fine - looks newish

Boost pipe is good

Opened up crossover - still no difference

Have not stripped lift pump yet - thats my next desperate attempt!!!!

As a kind of engineer I can tell its not reving.
 
Converging said:
Promise its nothing to do with the rev counters. You can feel the port engine does not have the power of starboard. The rev counters both go up to the rev range when shes in neutral.
Click to expand...

When troubleshooting over the internet it is real difficult when people do no post ACTUAL #'s that they are getting. As Volvopaul commented you have to have the strobed numbers, not the infomation off the gauges. All about data, data, data. High idle #'s WOT #'s. Boost pressure, data nails problems.

I have a bit of a VM blind side, but add this to the list by Volvopaul. Check lift pump outlet pressure, I do not have the spec to hand, but Bosch rotary fuel pumps generally need 15 psi from the lift pump. In the absence of actual data record lift pump pressure from good engine before checking and comparing numbers with the lazy motor.

Likewise assuming fuel filters are OK because they were changed last year is not the way forward. Filters certainly require changing one year on anyway. Lack of filter restriction gauges on European boats is always unhelpful.
 
Have you had the boost checked with a manometer, if its down it could be as simple as adjusting the waste gate a tad to get the boost up, if it doesn't respond then it could be the waste gate valve isn't seating properly or is cracked/damaged, either will give lower boost.
 
Latestarter1 said:
Likewise assuming fuel filters are OK because they were changed last year is not the way forward. Filters certainly require changing one year on anyway.
Click to expand...

I'll second that. Port engine was down on power and revs and I checked everything - fuel pickup pipes, swapped the lift pumps over, checked the boost pressure, pump pressure, had the injection pump rebuilt, all injectors checked.

The filters had been changed just before the injection pump rebuild and all the other work, and the Racors were still clear, but the problem went away when I replaced the engine filter for the second time. I did a post mortem and the filter was black with fine debris, while the starboard one was clear. Go figure...
 
Thanks for the advice:

Problem is as Joe ordinary I do not have the correct measuring devices. Cardiff marina is a bit bereft of Mercruiser VM expertise.

Take on board the filter comments. I will change them again.

Do they have to be marine filters or can I use a commercial ones. Current are Fleetguard FF105c.

Spannerman - I dont think the 3.6D is fitted with a waste gate. If it is I cannot find it.
 
Converging said:
Do they have to be marine filters or can I use a commercial ones. Current are Fleetguard FF105c.
Click to expand...

No, one of the best things you can do is get a list of equivalent part numbers - FRAM, Mann, Unipart, Coopers etc - that way you can always be sure of getting them somewhere. My only advice would be to go for a recognised name. Hint: the only time I have had unexplained filter trouble (see above) was when the only ones I could get hold of were Halfords ones...
 
Converging said:
Thanks for the advice:

Problem is as Joe ordinary I do not have the correct measuring devices. Cardiff marina is a bit bereft of Mercruiser VM expertise.

Take on board the filter comments. I will change them again.

Do they have to be marine filters or can I use a commercial ones. Current are Fleetguard FF105c.

Spannerman - I dont think the 3.6D is fitted with a waste gate. If it is I cannot find it.
Click to expand...

FF105 c are fine, yes the 3.6 hasnt got a wastegate but the 4.2 220 has.
 
Wiggo said:
No, one of the best things you can do is get a list of equivalent part numbers - FRAM, Mann, Unipart, Coopers etc - that way you can always be sure of getting them somewhere. My only advice would be to go for a recognised name. Hint: the only time I have had unexplained filter trouble (see above) was when the only ones I could get hold of were Halfords ones...
Click to expand...

Just personal but I am a bit of a Fleetguard or Mann fanatic dependant on make of motor, with Baldwin runner up. Fleetguard have just about the widest availability and keenest prices from commercial vehicle factors. FRAM did a range of branded filters for JCB a while back, caused some real engine probs..

Assume FF105c is the tiddly 'last chance' filter. What do you have as your bulk filter/water separator?? In other your 'rock stopper'.
 
Latestarter1 said:
Just personal but I am a bit of a Fleetguard or Mann fanatic dependant on make of motor, with Baldwin runner up. Fleetguard have just about the widest availability and keenest prices from commercial vehicle factors. FRAM did a range of branded filters for JCB a while back, caused some real engine probs..

Assume FF105c is the tiddly 'last chance' filter. What do you have as your bulk filter/water separator?? In other your 'rock stopper'.
Click to expand...

I have worked on this boat before he bought it.

The ff105c is the prefilter, it has a drain on it at the bottom, then its fuel to the lift pump and fine mercruisers own filter then to the injection pump.

Boat has had new rubber flexi fuel lines fitted last year.

My boat has the same prefilters on so the rate of flow is ok for 340 hp no probs, you can also see when there getting ready if you simply unscrew and look in the top as dirt collects there first on the ring of holes before it goes down and through the sides of the paper into the middle and up the centre of the filter.
 
Spannerman - I dont think the 3.6D is fitted with a waste gate. If it is I cannot find it.[/QUOTE]

Sorry for the duff info, its a long time since I saw one of these motors so have got a bit rusty in the memory dept!
 
Sorry for the duff info, its a long time since I saw one of these motors so have got a bit rusty in the memory dept!

No worries, at least now I know what one is and that I have not got one - so hey - thats one possibility solved!!!!:)
 
volvopaul said:
The ff105c is the prefilter, it has a drain on it at the bottom, then its fuel to the lift pump and fine mercruisers own filter then to the injection pump.

Boat has had new rubber flexi fuel lines fitted last year.

My boat has the same prefilters on so the rate of flow is ok for 340 hp no probs, you can also see when there getting ready if you simply unscrew and look in the top as dirt collects there first on the ring of holes before it goes down and through the sides of the paper into the middle and up the centre of the filter.
Click to expand...

I do not want to cause too much drift on this post, but I have a totally different perspective on fuel filteration. It was the advent of common rail systems requiring maximum of 2 micron at the last chance filter, with decent low restriction pre-filter life together with changes to diesel fuel which prompted a sensible look at marine filteration.

#1 Some builders standards are at best borderline, many plain unnaceptable. Certainly not designed with the end user in mind. Engine manufacturers have MINIMUM standards, no point in designing to to this, boats represent a different set of challenges with safety the primary consideration. Never forget, 'No engine has ever failed because fuel was too clean'.

#2 Too many people think of sizing in terms of Hp, it does not work that way. All about total fuel flow of your engine-not just the max rated fuel burn. It is typical to have a diesel engine rated at 300 HP (14.5 GPH max fuel consumption at rated WOT) but have a fuel flow of 58 GPH almost one gallon per minute! Your entire fuel delivery and filtration system needs to be sized for the max fuel flow and not just maximum fuel consumption. Remember Baldwin, Fleetguard and Racor spec sheets are in US Gallons, so when sizing a fuel system do not forget that they are only using baby gallons.

#3 Tankage, older fuel tanks will typically have something in the fuel tank that that you do not want your engine to burn or get anywhere near the "on-engine" or last chance filter that is part of the engine fuel system. Whether it is be some type of growth (algae), accumulated debris (diesel fines, sludge build-up, etc), water, internal tank coatings that are deteriorating, there is always something in there that should not make it past your off engine primary system. In addition consider this the new off road fuel, due for introduction later this year has an organic (biodiesel) element which will stir up all manner of long dormant tank crud and a fuel which will have greater affinity for water.

#4 Racor MA Series is O.K. as a starting point, however it is messy to clean, as component part of a multi stage system is fine. Modern spin on filters make the most sense, and the ancient CAV type filters with cellulose media no longer have any place in a marine fuel system.

Returning to the original discussion, Fleetguard FF105c or eqivalent Baldwin Racor or MANN as the pre filter, I would use some lateral thought here, consider upgrade to FS1000 or eqivalent, I am certain both use the same filter head pattern. FS 1000 has better capacity, dual pass 10/5 micron at second pass, far better water coalesing properties with the bonus that it comes out at similar pricing to the little marine only FF105c, as it has high useage in the commercial vehicle sector.
 
there comes a time when trying this and trying that can cause other problems and even hide the original problem, the best time to find a fault is before other things have been adjusted or changed.

Perhaps call in the experts, the cost of diagnosis may be far less than the cost of trial and error
 
You must log in or register to reply here.

Share this page

Top