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Thread: 2.7 heads on 3.0
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05-08-2011, 12:47 AM #61Scream And Fly VIP
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grinding on a good engine while its together is risky, it only takes a small amount of debres to ruin it. Now if its junk to start ok but I wouldn.t risk ruining a block. If you raise the exhaust it will suffer on the bottom without compression.
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05-09-2011, 10:43 AM #62
Thanks for the input and advice. I think I will leave the ports original for this season and just do heads and jetting. Then I can look at the boat for more performance, jackplate / bracket and prop.
Hal
"Ton o' metalflake" 1982 Concord Mach II with 1997 Johnson 225 Venom
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10-13-2011, 02:27 PM #637000 RPM
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Just got a set of 2.7 heads to go on my 200 Johnson. They look to be in good shape. Any tips or. Advice
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10-13-2011, 04:31 PM #64
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10-13-2011, 04:50 PM #65
if it"s a 92 or older back the timing down to 16 degrees from 18 jet up two sizes one or two more on the bottom two cylinders if they were not already richer than the top four. fill the relief holes , and install 106 pullovers in the from bottom vent holes in the carbs. This brings the main jets in earlier. with the relief holes plugged and .700 deep chamber #331490 heads on my 89 the compression jumped from 85lbs to 140lbs.as said above run good super , without ethanol if you can get it.
Steve
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10-13-2011, 08:17 PM #667000 RPM
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My motor is a 99, so is it the same procedure? Not sure what 106 pullovers are. Wasn't planning On plugging the reliefs yet. Just trying to find out what else needs to be done.
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10-14-2011, 09:03 AM #67
no 99 is a closed deck, and you will need to do a cooling mod. Racer, who posted above can tell you exactly what to do. Your carbs are also a little different , so I would ask racer as well as I have not worked on them before.you might be just as well off having your heads machined if they are the ocean pro style. pm racer if he does not chime in here.
Steve
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10-14-2011, 10:38 AM #687000 RPM
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I sent him a pm yesterday, havent heard from him yet. I talked to baha200merc and he said i would prob need to go up 2 sizes on the top 4 and 4 on the lower 2. I'm going to wait to hear from racer.
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10-26-2011, 06:53 PM #697000 RPM
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Well I swapped out one side to the 2.7 heads today and did a comp check. Stock heads I was at
100psi on the nose, with the 2.7 heads it bumped it up to 120 on the nose. Not to bad, that's with the idle releifs open. I swapped back to the stock heads for now, I need to get the thermostats
ordered because the heads didn't have any in it. Im going to clean and paint them before I put the heads back on.
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10-26-2011, 07:00 PM #70
Can you post some details on the cooling mod? I also have a 1999 Johnson 200 and I'm kicking around the idea of doing this for next year. I was under the impression that the hose routing was different too. Any truth to that? I'd be interested where you end up for jetting too.
JohnI was going so slow I almost crashed. - JamesGang
1978 24 Superboat - 250 EFI
Sold: 1991 Starliner - 250 EFI Merc 3.0
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10-26-2011, 07:09 PM #717000 RPM
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There are a few different cooling mods that people talk about, some say fill the heads in-between
the cylinders with marine Tex, there is another mod that requires taking the motor apart a bit to change some things. I've been told it's not rely needed. The thermostats and hose routing is a little different, but nothing that should be a prob. As far as jetting that's a debate in itself, I hope to not rejet, I've been told that my motor is running to rich as it is so I hope the heads help. Apparently it's "4 stroking" when cursing.
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10-26-2011, 07:17 PM #72
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10-26-2011, 08:00 PM #737000 RPM
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Well maybe 4 stroking is wrong, but if it's running rich wouldnt it all even out? I understand you jet for load also, heavier load bigger jets, I'm sure the stock jets were for a much bigger and heavier boat, so if it's rich now and I put bigger jets wouldn't it still be rich? So if it does need jets, 2 sizes? So i think it would be 69d. It's so hard to get a consistent answer.
Last edited by Gorilla0178; 10-28-2011 at 04:03 PM.
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10-27-2011, 09:31 AM #74
No one will answer your jetting questions since they are not there to check for them self. No one wants to see you hurt your motor with jets that are too small. Start big take small steps down and dont look at the plugs, if you end up putting jets in it that are too lean by the time the plugs are colored it will be blown up. You have to look at the piston tops from the intake ports.
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10-27-2011, 10:08 AM #75
I have a closed deck block and I have not done any cooling mods. I've been running cut 3 liter heads for at least 5 years @about 130psi and not had any issues. My carbs were already jetted fat from the get-go though. The only mod I've made since bumping compression was dry-stacking the exhaust.