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Old 11-07-2010, 05:32 PM   #1
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Country: Spain
Location: Mallorca
Occupation: Marine Service Manager
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Boat make: Phantom 21
Engines: Merc 135hp/merc XR2
Cruising area: Balearics

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Blown motor........!

hrew the boat in the water today and had great fun untill the motor went on sick leave.

I have just rebuilt the motor ( 2l 135hp Mercury 2000) after buying it with a fault, when running flat out it slowed down ........let it cool down and it would be fine again.........? this was only happening at flat out (WOT).

So stripped it threw in 2 new top pistons (which were scored ) did away with the oil system and running it on premix.

first time out today ran it around for a few hours and was fine, was running it about 3k rpms and every 10mins ran it upto 4/5k and seemed to be OK. then on the way back ran it flat out 6kish and it started to slow on the pistons backed off a little and went a bit longer then floored it again and it siezed and stopped!!!!!!!!!!!!

So before i start ripping it apart again whats the likely cause??? i wanna say lack of oil but was running it on 25:1??????.

I have had an XR2 do a similar thing due to a blocked carb, but my carbs were cleaned and rebuilt last week??? just before i ran it??


Any ideas chaps would be greatly recieved...

thanks
Matt
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Old 11-07-2010, 05:54 PM   #2
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Country: Spain
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Boat name: Patriot and Forca
Boat make: Phantom 21. Falcon Bonito 36
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Hi Matt, I'm running 50:1. I thought this was the norm. Pete
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Old 11-07-2010, 06:03 PM   #3
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Country: UK
Location: Guernsey
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Engines: 2.5 EFI
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25:1 is wayy to much oil, more oil thickens the mix and the fuel travels slower through the jets actually making it run lean
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Old 11-07-2010, 06:14 PM   #4
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Country: Spain
Location: Mallorca
Occupation: Marine Service Manager
Interests: Boats,bikes and rally cars
Boat make: Phantom 21
Engines: Merc 135hp/merc XR2
Cruising area: Balearics

Join Date: Jun 2009
Location: Mallorca
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i was running 25:1 for the first tank as it had new 2 new pistons and all new rings???? thought i would run it with a bit much oil to help, then the plan was 50:1 in the next tank???

makes sense what you are saying Scooby Hugh,
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Old 11-07-2010, 07:04 PM   #5
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Country: uk
Location: Guernsey Channel island
Occupation: wholesale food sales
Interests: Burning fuel!!!
Boat name: The Magician, A Fine Pair
Boat make: ring20b, chriscraft stinger 26
Engines: merc XR2, 2X AQ311B 5.7's
Cruising area: channel islands

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Location: Guernsey Channel island
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25/1 is fine for a run in period,

after that i run my XR2 33/1, yeah it smokes a lot but keeps the motor sweet.

what kind of fuel pump does your motor run? is it a diaphram vacume type pump or en elec extermal pump?
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Old 12-07-2010, 09:39 AM   #6
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Country: Spain
Location: Mallorca
Occupation: Marine Service Manager
Interests: Boats,bikes and rally cars
Boat make: Phantom 21
Engines: Merc 135hp/merc XR2
Cruising area: Balearics

Join Date: Jun 2009
Location: Mallorca
Posts: 56
Running just the stnd engine/block fuel pump.
Which i put new gaskets and diaphrams in only a few weeks ago. I have always found those stnd merc pumps pretty good???

Going off to take the heads off in a bit to see the damage???

Just thinking back it did get a little noisey just before it stopped so would that spell out lack of oil???
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Old 12-07-2010, 09:52 AM   #7
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raced mine for 3 yrs on 30/1 and never missed a beat,including pleasure use
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Old 12-07-2010, 12:44 PM   #8
Le Cat
 
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Your piston break in time seems short, how many hours before you went to 6k rpm ?
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Old 12-07-2010, 01:30 PM   #9
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Country: Spain
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Interests: Boats,bikes and rally cars
Boat make: Phantom 21
Engines: Merc 135hp/merc XR2
Cruising area: Balearics

Join Date: Jun 2009
Location: Mallorca
Posts: 56
probally 3 .5 hours total??? i replaced the 2 top pistons and all the rings????

your probally right , i did get a bit over excited. i did think short burst would be OK????
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