Jamie Dundee
Well-known member
If this were a boat with an outboard everything would point to it being over propped. I’m a basic maintenance only mechanic so can’t really suggest any more than you’ve already done.
Nanni 4.390 saga continues (low power low speed)
- Thread starter freddyuk
- Start date
freddyuk
Active member
We will have more info this weekend......
CO86
New member
Hi Freddy,
For reference, i have a mf805 with a nanni 4.390, she’s nearly 1500 hours. Ours produces next to no steam at 7 knots, with slightly more being evident at 3000rpm cruise but still very little.
Ours maxes out at 3400rpm, that gives us 20knots. We haven’t bothered investigating the missing 200rmp, could be something as simple as throttle cable adjustment but i never run it beyond our 3000rpm cruise except for short blasts. Have you checked you getting full throttle cable travel?
At about 1750-1800 we get 7 knots.
At 3000rpm, 13-15 knots. Full fuel, full water and 3 VERY well feed men!
For reference, i have a mf805 with a nanni 4.390, she’s nearly 1500 hours. Ours produces next to no steam at 7 knots, with slightly more being evident at 3000rpm cruise but still very little.
Ours maxes out at 3400rpm, that gives us 20knots. We haven’t bothered investigating the missing 200rmp, could be something as simple as throttle cable adjustment but i never run it beyond our 3000rpm cruise except for short blasts. Have you checked you getting full throttle cable travel?
At about 1750-1800 we get 7 knots.
At 3000rpm, 13-15 knots. Full fuel, full water and 3 VERY well feed men!
freddyuk
Active member
What a spectacular morning here in West Cork. No wind, no cloud and dolphins to boot.
Did the trip over to the marina for seacock repair, weighing and propeller check and tested engine on the way. Initially pootled along at 6kts enjoying the morning. Then after some 30 minutes put into idle with temperature sticking at 75-80c and checked the exhaust. It was easy to see what was coming out in the calm conditions - quite a bit of oil smoke. See clip...
https://youtu.be/2ecYjz3AiLA
Then I did a fast run as I had taken some weight off the boat and was one up. Eventually got to 17kts/16.8kts variable at WOT 3400 revs. We were on the plane but at full chat. I then throttled back to 3000 revs and she came off the plane and fell back to 12kts.
Did the trip over to the marina for seacock repair, weighing and propeller check and tested engine on the way. Initially pootled along at 6kts enjoying the morning. Then after some 30 minutes put into idle with temperature sticking at 75-80c and checked the exhaust. It was easy to see what was coming out in the calm conditions - quite a bit of oil smoke. See clip...
https://youtu.be/2ecYjz3AiLA
Then I did a fast run as I had taken some weight off the boat and was one up. Eventually got to 17kts/16.8kts variable at WOT 3400 revs. We were on the plane but at full chat. I then throttled back to 3000 revs and she came off the plane and fell back to 12kts.
penfold
Well-known member
Hard to judge from a video but it doesn't look like oil smoke, the speed it dissipates suggests unburnt fuel or steam. Does it smell like lube oil?
freddyuk
Active member
Its deffo blue and not steam as i get steam when tramping on and it dissipates much quicker. This floats across the water for quite a while. It is the same smoke i get a start up.
freddyuk
Active member
OK the boat has been lifted and I have a prop covered in barnacles. This was cleaned and treated end of last year.
It would lose me some speed but 200 revs as well?
There is the prop numbering but I do not know if this is correct for the MF805 ?
It would lose me some speed but 200 revs as well?
There is the prop numbering but I do not know if this is correct for the MF805 ?
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ChromeDome
Well-known member
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Jamie Dundee
Well-known member
Mine has more pitch than that (23.6”) and the same diameter, your boat is slightly bigger so looks about right, providing the gearbox ratios are the same.
Bilgediver
Well-known member
Sounds good. I would check the aftercooler if there is one and also confirm the turbo compressor is not oil contaminated as on oil film and dust on these components can case a 10% drop n efficient. We used to wash the turbos and aftercooler on engines I used to operate and the increase in efficiency was noticeable.
You say that you cleaned the boat at the start of the year. Has it been ashore for the last 7 Months?
You say that you cleaned the boat at the start of the year. Has it been ashore for the last 7 Months?
freddyuk
Active member
Its been in the marina. Bottom was slightly slimey but prop is unbelievable in 6 months. I will collect monday and test run it back to compare with yesterday. Turbo has not been touched. I will test boost pressure next week. Hard to get bits here if i start stripping stuff
Bilgediver
Well-known member
Do you have plugs or something that can be removed on the aftercooler to check pressure drop. Using a simple U-tube arrangement . Don't need to dismantle to check performance.
penfold
Well-known member
Barnacles aren't helping, either on the prop or the shaft; it's hard to judge from the pic but the AF doesn't look very smooth either, although it was taken before cleaning so might just be slime.
CO86
New member
From memory Freddy my prop is the exact same. Will try and dig out pictures i took on my phone.
vas
Well-known member
Lost revs could v.easily be from these barnacles. 6m in a marina idle, mine wouldn't even plane...
Re testing turbo boost, there should be a blank or two somewhere along the inlet plenum -dont mess with the wastegate pipework! If you find one, undo it make sure it goes down through to the inevitably oily plenum, find a matching thread 6-8mm nipple, a few m of silicone tubing and a decent quality wika 0-3bar boost gauge. Fit the lot up and test it! Shouldn't cost you more than 40quid from a hardware/toolshop.
Alternatively remove the air filter and WITH ENGINE TURNED OFF check if the turbo rotor spins smoothly and if there is any play.
Mind bet you get two knots from cleaning hull shaft and prop!
Cheers
V
Re testing turbo boost, there should be a blank or two somewhere along the inlet plenum -dont mess with the wastegate pipework! If you find one, undo it make sure it goes down through to the inevitably oily plenum, find a matching thread 6-8mm nipple, a few m of silicone tubing and a decent quality wika 0-3bar boost gauge. Fit the lot up and test it! Shouldn't cost you more than 40quid from a hardware/toolshop.
Alternatively remove the air filter and WITH ENGINE TURNED OFF check if the turbo rotor spins smoothly and if there is any play.
Mind bet you get two knots from cleaning hull shaft and prop!
Cheers
V
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Jamie Dundee
Well-known member
You also appear to be missing a prop anode.
freddyuk
Active member
I thought the anode was the conical fitting on the end of the shaft. That was replaced when I bought the boat but that is nearly 2 years ago. Then anodes were replaced when the antifoul and prop cleaning was done in November according to my bill. I am just wondering if those huge barnacles could grow that fast in 6 months? I was reading it takes 6 months for the attached larvae to become adult barnacles with the hard shell. The work was done just before lockdown so I didn't get the boat back for quite a while.
I will report the speed gain on Monday.
I will also check the turbo as far as I can. I can probably get the airfilter off. The heat exchangers were all cleaned during the service in 2020.
I will report the speed gain on Monday.
I will also check the turbo as far as I can. I can probably get the airfilter off. The heat exchangers were all cleaned during the service in 2020.
Jamie Dundee
Well-known member
Yes, but it’s missing. You can see the Allen screw where it should be. Mine are wearing out in 3-4 months.
freddyuk
Active member
Oh right thanks. I better get a box then. Is this an electrical problem dissolving them that quick?
jamie langstone
Active member
my anode last 6 months on my MF805
