new to me 308
09-16-2014, 09:09 AM
#111
Platinum Member
Platinum MemberThread Starter
never mind guys I have two on order...may need a little help getting the cg right but it should haul @ss with these babies on it 
[ATTACH=CONFIG]529651[/ATTACH]
[ATTACH=CONFIG]529651[/ATTACH]
09-17-2014, 06:10 AM
#113
Registered
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I'm curious too. Looks like a V-8 with exhaust manifolds whose exhaust pipes are directed down and to the rear?
I'm curious too. Looks like a V-8 with exhaust manifolds whose exhaust pipes are directed down and to the rear?
01-16-2015, 01:43 PM
#115
Platinum Member
Platinum MemberThread Starter
I have gone ahead and purchased two Mercury Power heads. can't wait on those 500# 400hp dream engines any longer...summer will be here before we know it!!!
01-28-2015, 07:17 AM
#116
Platinum Member
Platinum MemberThread Starter
powerheads arrived...will be a week or so before the shop has room. 3 CC's getting brand new 300's. there were 10 new ones sitting at the shop when I ordered my powerheads! lots of $$$$$ on the ground LOL.
01-28-2015, 04:35 PM
#118
Registered
LA, After all my research and discussions I have come to the conclusion that two things contributed to my 300XS failure. 1. Too much idle on the "broke" motor due to a gearcase issue on the other one which caused me to idle back to my dock (approx. 1 hour). This is the consensus with Mercury corporate and my master mercury tech who I have a lot of respect. Mercury break-in procedure warns against ANY idling until broken-in. 2. Nass cowls WITHOUT the DBR upgrade. Joe at DBR claims that the ECU just cannot compensate for the ram-air created at hyper 100MPH speeds. He says Mercury has them tuned to the lean limit to pass CARB emissions. Just a word of warning if your are stressing your motors at high speed. I found this condition to be true on a multi-port injected 351 in my Donzi that I highly modified. Got a tuning program (Tweecer) and a base tune which put it back in the sweet spot, eliminating the very lean condition. Then was able to fine tune the map for air/fuel, spark, etc. The ECU just could not compensate for the increased air flow. My two cents. David
01-28-2015, 07:40 PM
#119
Registered
iTrader: (1)
LA, After all my research and discussions I have come to the conclusion that two things contributed to my 300XS failure. 1. Too much idle on the "broke" motor due to a gearcase issue on the other one which caused me to idle back to my dock (approx. 1 hour). This is the consensus with Mercury corporate and my master mercury tech who I have a lot of respect. Mercury break-in procedure warns against ANY idling until broken-in. 2. Nass cowls WITHOUT the DBR upgrade. Joe at DBR claims that the ECU just cannot compensate for the ram-air created at hyper 100MPH speeds. He says Mercury has them tuned to the lean limit to pass CARB emissions. Just a word of warning if your are stressing your motors at high speed. I found this condition to be true on a multi-port injected 351 in my Donzi that I highly modified. Got a tuning program (Tweecer) and a base tune which put it back in the sweet spot, eliminating the very lean condition. Then was able to fine tune the map for air/fuel, spark, etc. The ECU just could not compensate for the increased air flow. My two cents. David
1) I live in a area where in the winter months there are long idle zones for Manatee's we never see! I have idled my boat for over hour at time with no issues. I have had friends with these motors on a offshore fishing b boat and they idle for 4-5hrs at time. Again no issues.
2) I kinda agree with DBR and I dont. Would you agree that if you are located at a high elevation where the air is thinner the motor would run richer? I believe based on the ECU's of today there is enough compensation to make up for the cowlings. If you look at Jim's (Zero's) Skater he has been running those cowlings for over a year with no issues and no DBR upgrades ( or so he says LOL). The boat he rigged spent the summer in Canada with the cowlings also. No issues. However air flow at a 100 could be sort of a ram air effect but keep in mind the cowling is not totally sealed and it will relieve some of the pressure through the drain holes. With Jim's help in a few weeks we will know for sure if the DBR upgrades hurts, helps or does nothing when I bring my boxes to the keys and we do a test. Craig, once the powerheads are broke in make a run, shut it down and do a plug check. Another option is install pyrometers like I did and you will see if the motor goes lean at anytime. I feel they are a necessity.
3) Lastly I blew a powerhead also with Stock set up no mods when they were new also. Not to mention there is another blown up 300xs powerhead at TNT recently off Gary Balough's 32 Skater. These things blow up plain and simple. These are really production motors built on a assembly line not at Mercury Racing like motors of old.
4) Lastly I agree with the breakin is important, good oil, quality fuel, and I run ACES in my motors along with Boostane now also just for kicks. Some of the big cat guys down here have reported good results with it on the 1350's.
Good Stuff guys,
