LOOPER TECH TIP's.........

[racer]

Several good points made by Gary, Lokintuz and Power. To fully understand the cooling issue it helps to have a block in several sections and being able to repeat tests is critical. The angle Gary is cutting leading into the chamber does help relieve detonation because the squish band is too wide for running over 6000rpm. I can tell you a deep narrow chamber is more detonation prone than a wider shallower chamber with the same CC volume, now take that wide shallow head and make the corner tight and it makes more power but you best be right on with timing and jetting. The factory adds a radius to the stock head in Garys second photo to give it some room adding the 45 raises the rpm band of the head. I am working on rechambering the closed deck head since the 2.7 is NLA, I am recutting the entire chamber. Have cut several up yet still looking for a good balance in power/safety while retaining head integrity (thats the tough part right now). I test the chamber design on removable chamber billet heads as it quicker and easier to do.

[racer]

Two issues that has been noted several times on this board is no ratchet in the lower unit and the carbs being lean in the middle. The non ratchet makes the carb issue worse. Adding pull over tubes helps and making sure your mid range jetting is very safe. I do have a way to make even a mod engine like Lokinutz 4 stroke problem is its very hard to explain and done wrong will ruin the carb, I did the mod to Darrens carbs and he actually had to lean down his mid jetting. Before you ask Darren was sworn to keep it quite, last he and I talked even after full disassembly he could not find one part and a critical part to making this work. This is a mod for big bores on mid bores they are way rich and ruins the carb. If you have a basic stock engine I would run a 106 pull over and as more mods are done go smaller, light clean up with 140 psi more like a .093 and so on. I hope this helps.

[Instigator]

Good stuff Al. Thanks for contributing.

I play with the pull overs on everything hot rod that I play with. Makes a huge difference in tuning.

I tap the pull over hole to accept screw in main jets. Perfect use for the old drilled out **** jets everyone tries to run in these things.

[Scmarineperformance]

nice thread but lets not forget about the top bearing caps bolt that back out and the occasional voltage regulator failure or poor connections to it in salt water apps that eats the head gasket and block surfaces.

[powerabout]

loctite?

[baja200merk]

Interesting stuff, thanks for posting Al.

Good stuff Al. Thanks for contributing.

I play with the pull overs on everything hot rod that I play with. Makes a huge difference in tuning.

I tap the pull over hole to accept screw in main jets. Perfect use for the old drilled out **** jets everyone tries to run in these things.

I have a set of big bores with a brass tube pressed into the carb and its tapped for idle/mid air bleeds.

Beef had an 88 225 on his mirage last month it had about 80-90psi compression with the stock 809s. We put my cut Mad EFI heads on it with thick gaskets and the compression reliefs open and it bumped it to 150psi . We also pulled the air box re-jetted and put pullovers in the stock carbs. When we returned it to stock and forgot to remove the pullovers it would not run at all. It just 4 stroked the whole time, we yanked them out put the air box back on and it cleaned right up ran perfect, was a huge difference.

I saw you put mainjets in the pullovers on that 3.0 you did. I like the idea because beefs motor vibrated 3 pullover tubes out, I found 1 in the reed cage the other 2 went through the motor oh well its still running

[Instigator]

Now I know why the Sonic motor popped.

Went to change my mid range jets from the 27's I had it in (30's were stock) to 28's or 29's to perk up the mid range a bit when I found 30's in all 12 carbs
So I'm running more compression and porting w/stock mid range jets........................, good

My notes even show 27's in them???
After dwelling on it for a while, I now remember leaning out the mid range when I first ran those motors w/the Bravo 1's on them. Boat was a slug and I wrote it off to pig fat break in jets when in reality it was a combination of 3/4" more diameter than I'm used to, and an additional blade, but the worst part..................................., no exhaust reliefs in the props. Doh!
I figured that out about the time I swapped motors for the stock 250's that Paul now owns.
Then, forgot about re-jetting my motors. Can't believe they ran as long as they did. 2 steps fat on the mains is the only reason they did.

DOH!

[jphii]

Man, I hate it when I do stuff like that.... Glad you found it.

[Instigator]

Glad you found it.

Yep, no kiddin. Was looking at the next step being dropping compression or running 93 octane and at 89 gls per, I didn't want to do that.
That was part of the challenge w/those motors was to get as much power as I could and be able to keep them alive on crap/cheap gas.

[bullet20vee]

I hate to bring up an old thread, but I have an 89 225 that I want to update the cooling system. Will these mods shown work better that the 1992 70hp mods? I just want to make sure that I don't cook my motor.

[powerabout]

Thought this might me a fun idea for some of you trying to keep these old dinosaur's running.
In struggling to get the 250 HO looper's running right that I built for the Sonic and now the 250 stocker's that I bought to temporarily replace them I've run across some of the odd ball issues that don't show up very often and most are not in a manual. They can stump you if not careful/lucky and figured this would be a good way to document them for others future benefit.
Also, any of you guys that have run across similar odd ball head aches or have comments on what I've found/done, feel free to add to the list. Not meaning for this to be a BS session or a place for you to post your problems for us to solve but kind of a reference point to "search" when you get stumped on something along the way.

Be very interested in comments from Racer and any of the other OMC Wizards on board.

Here's todays list.






#8. Top two cylinders run hot and lead to catastrophic detonation. I eluded to this in #6 above. Common wisdom says that due to really poor exhaust scavenging on the bottom two holes of a V-6 looper, those holes run hot and they do. But the factory put's 2 cc's of additional combustion chamber volume (why compression is 5 lbs lower on those two holes) in those two (one on each side) holes to combat this and IMO this works pretty well.
I think at least 99% of the dead V-6's I've opened up have had a dead #1 or #2 on the top. My opinion is that the block struggles to stay filled with cooling water in that area. I and others have done a bunch of work to combat this on the hot rod motors.
Some potential issues are over heating which causes the cooling water to boil (inside top of block) which makes steam and that equals pressure which fights the cooling water trying to get there. Once that happens we're back into detonation prime time!
I can tell you that EVERY one of my hot rod motors I've popped since being down here has been from detonation (all from inadequate octane levels which was my fault) and ALL have been a top hole. I think a worn water pump (excess motor height) can start this and if you have ring sticking/coking beginning also, you're done!
Once my motors are dialed on the Sonic they will both be jetted 1 step higher on #1 and 2.


There you go kids. Hope you enjoy it cuz it took me 1/2 a day to type it

Hi Instigator
I wondered if anyone ever looked at reversing the water flow in the engine, cooler heads and hotter chest and all that?

[Instigator]

Bring this to the top for some of the people asking me for help.

[Captain75]

Gary you had a 3.3 gasket on the 3.0 I had why are you running 3.0s on your engines?

Forgot about this thread and just stumbled upon it again.

Here's one I just did after popping one of my Sonic motors due toooooooo......, wait for it.........., DETONATION
Guess which hole too..............................?????????????????? #2.
I think I've now popped 4 of my p.heads since we've been down here (7 yrs) in Fla. All four from detonation, and all four #2.
Matter of fact, I think every popped motor I've bought down here ( 20 or 30) has lost #2.

The Sonic motors are pig fat rich and still knocked the skirt off a piston. I knew I was on the edge w/compression vs octane and since I don't listen to anyone else.......

Anyhow, heres the cooling mod very similar to what I did to the 3.3 mod motor and don't think I posted pix's of it. This is one of the Sonic motors and I've now done the mod to both.

In the completed picture you have to look close to see the hoses behind the coils. I like keeping my motors stock appearing.
I pulled the hoses with the motor running and I'm getting a steady flow of water (from hose and block) at idle. What my read is, is that after a mid/high speed blast, when you back off, the water pump slows down and the tops of #2 uncover from cooling water. These motors already run way lean at mid range, so the combustion chambers are already hot,, uncover the tops of the cylinders and powie!

Funny thing too. was looking at a 3.3 p.head base gasket and I think it reverses cooling flow compared to the 3.0's. I know I tested both on the 3.3 and ended up w/the 3.0 gasket but I think only after doing this mod. The gasket may do it. Course you then have to pull the p.head to install it.

So now the question is, do I have the stones to run these motors again on the same octane to accurately test the effects of my mod's Serious doubts..

Bottom of block at exhaust.



Top of block. (both are 1/8" npt by 1/4" hose barb)



Completed.

Can these pictures be wiewed somewhere?

[baja200merk]

Gary later informed me that someone swapped the gasket to a 3.3 afterwards but it did stay cool even well over 100mph. He originally installed a 3.0.

Carb 3.0 need some changes to run 3.3 gaskets. Google the cooling diagrams and compare them.

[Instigator]

Hi Instigator
I wondered if anyone ever looked at reversing the water flow in the engine, cooler heads and hotter chest and all that?

Was just reviewing all Ive forgotten and saw I missed your question.
Talked about with someone but dont remember if they actually did it.

I like the idea.