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Thread: Looks too loose to me ..
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09-23-2017, 08:01 AM #61Member
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The term we use in the far north is "she's counter balanced well"
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09-23-2017, 10:29 AM #62
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09-23-2017, 10:55 AM #63
From another thread:
Very first thing that comes to mind is the upper mount. I know you said you have solid mounts . I did the same thing years back when the double hump mount cover broke . Then I added a girdle over the top and then the three bolts that hold the cap down broke .
Mercury went to a solid ( no bolts no cap ) one piece mount in their 2001`and up engine adapter plate on 250 / 300 HP models .
Not sure what you have or it's condition , but it's worth a look and an upgrade if you are still running the early model parts .
So now that we have the tiller arm securely fastened to the engine the next weak link in line is the relation between the lower yoke and swivel pin . The factory uses a wave washer to take up excessive slack and pits a clip at the bottom and calls it a day.
For offshore race boats , I machine a 316L tube that runs the entire length of the swivel pin that is welded in place that has threads sticking out from the bottom of the pin that uses a cup and nut arrangement to secure that junction .
For single engine or river runners that don't have the need for a double walled swivel pin I make a shorty version that does the same thing with less machining and welding time as well as a few pounds less weight.
Both use a shim stack I cherry picked out of different models .
End result has been no more broken mid section parts . Longer lasting swivel pin bushings and better handling on single V hulls .
As Joe said , this is something that sensei Scott Porta' taught me a few years ago . I'd like to think that I took the pebble from his hand and improved on material selection and application since then. I just did a set that are going to him . I'm sure the teacher will be pleased ...
Chaz
I CAN ALWAYS MAKE ANOTHER DOLLAR, BUT I CANNOT MAKE ANOTHER DAY
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NICE PAIR liked this post
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09-23-2017, 11:05 AM #64
Chaz,
You cut open the chest to gain access for some clean up? Guessing not many have seen the inside of those?I CAN ALWAYS MAKE ANOTHER DOLLAR, BUT I CANNOT MAKE ANOTHER DAY
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NICE PAIR liked this post
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09-23-2017, 12:45 PM #65Member
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If you are running a high performance boat at speed and have one of these motors I highly suggest you make this modification. The design was not intended to do what we do in rough water.
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09-24-2017, 12:02 AM #66
Not really sure what your asking . But I'm going to guess you mean the rod slot area .
I've seen a lot of 280 blocks that have come thru here that had the top of the slot laid back to feed the boost port and a couple that had the whole thing trenched to aim a channel at all transfer openings .
I really don't agree with that . Here's why . As the piston pulls away from BDC it creates a vacuum which peaks at 90* before TDC . A good 30+ degrees after the transfer ports close . Air is going to follow the path of least resistance , which is right behind the piston . Even if you try to aim it off to the sides , it's got no reason to go into a closed area that is being subject to increased vacuum as the piston moves upward .
If anything , the rod slot should be funnel shaped allowing for easy passage from the lower crankcase to the cylinder base and then shown a smaller window to migrate back into the crankcase ..
More wifes tales and monkey see monkey do is to cut the front half ...
So go ahead and pour the crank case . 1000 cc now cut the beloved .050
Congratulations you are the proud owner of a 997 cc crankcase ...
Worse part is you have now moved the reed pedals closer to the rod cap wizzin past . Ever wonder why your reed pedals are burned and chipped on the Top RH corner .
Yep they been doin the wave like shingles in a Hurricane ...
I know it's easy to clamp a flat surface to a flat table and clip the flat surface facing up .. but I'll bet the real power brokers are filling the open spaces where rotating parts aren't . And closing the door by 30 cc's not 3 ...
That was the other side you were talkin about .. weren't it ...
DavidLake :
Chaz, I remember reading something about the "slop stop". Can you elaborate on it? Do you do this work?
MidLife :
Chaz,
You cut open the chest to gain access for some clean up? Guessing not many have seen the inside of those?
A few years ago I band sawed a block into sections so I could see how thick different areas were . There is enough meat to get a pretty decent short side turn from the ex. port into the log , but I haven't found a way to get the last 10% with out popping the lid off . There are a few places along the long side I like to build up with weld as well .
I've been working on an exhaust kit in all my "spare time". I'll know a lil after Jasper if it needs to go on the market , or in the scrap pile ...
I can't speak for others , but I would imagine that the OMC guys who have spent some quality time with these motors , have broke out the knife and took a peek inside .
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Freddie Webb liked this post
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09-24-2017, 12:35 AM #67
Chaz, do you leave a lip around the funneled rod slot to resist flow back into the plenum area?
Think I've seen pics of a few Looper filets around somewhere.I CAN ALWAYS MAKE ANOTHER DOLLAR, BUT I CANNOT MAKE ANOTHER DAY
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09-24-2017, 07:58 AM #68
I haven't actually tried to out trick myself yet . But my mind does wander a bit ..
I think the best a guy can do is to lay the crank in the block and correct any mismatch's . Then lay it in the front half and do the same . The inner crank wall's really dictate the path .
The entry to any hallway should be beveled to align the column .
As far as exit's go ...
The factory keeps the walls straight with a little bevel to break the edge and funnels both ends.
I think a lot of people go to big -too quick and open the floor up to where it looks like the end of a blunderbuss that looks like it will flow better in reverse than forward.
The flow bench junkies I know follow the 7* taper rule .
Old school shear plates took big standoff's to control backflow .
The "scientists of the wind" seem to be moving into more of a "backside trench" these days to accomplish the same thing without the big drop's hanging down .
This technology even seems to fit the outboard motor's layout . All it takes is a long tapered shank end mill to reach down inside ...
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09-24-2017, 08:32 AM #69Screaming And Flying!
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re rod slot
how much more power/ci does an inline make that doesnt have rod slots?
OMC 31 M, say 125hp for 49ci
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09-24-2017, 11:27 AM #70
Power ,
Brother your just gonna-hafta dyno them ... and one of these and get back to us ...
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09-24-2017, 06:28 PM #71Screaming And Flying!
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gears and a pipe is a whole other deal
I was trying to compare with an inline 2 stroke outboard
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09-25-2017, 07:06 AM #725000 RPM
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09-25-2017, 07:21 AM #73
Chaz, another curiosity question. I haven't fooled with a lot of 3.0l so enjoy threads like this to learn. Thanks for the great info! When I degreed a non opti EFI 225 it had like 32 degrees blowdown. What is the reasoning behind this on a motor that doesn't turn that much rpm? Or they compensating for a weak exhaust/ lazy intake or what? Or is it an emission thing? And do you make any changes to that after your mods? We widened the exhaust ports, done some epoxy work on intake side and lowered to like 30 degrees blowdown by raising transfers and picked up almost 300 rpm. Didn't want to do too much not being familiar with them, just wanted to see how it reacted. Have some ideas for next time after our results, but would love your input on this? Could save me some heartache
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09-25-2017, 07:29 AM #74
Now Power , I can find you a picture of some transmission and expansion chamber pictures if need be ... cuz I didn't see any in the ones I posted ..
OK , I'll go with your numbers . Your non descript 49 inch motor off the top of my head made aprox 2.5 hp/ci . a 3.0L -185 ci @ 300hp would be around 1.5 hp/ci and it would have to make 400 hp to be over 2 hp/ci .
I did a 90 hp bottom loaded L3 that looked like the parts were pulled out of the 2.5 and 3.0L parts bins . Wide open crankcase , call it half a 2.5 . 75 inch's and 90 hp don't look real good ... so throw that theory out the window . One is a low cost throw away , one was built as a fishin motor and the other seems like it was built for racing .
Since I was pretty sure you wouldn't return with fresh dyno sheets , my intention was to notice port lay out .
Lets start here ....
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09-25-2017, 07:53 AM #75Screaming And Flying!
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Yes I can understand bike engines as they have plenty of clearance between the cylinders.
What are you getting at in the port layout, i'm listening.
What i am trying to allude to is are the rod slots in a v an issue?
That 31 M is a custom omc race engine designed after years of 3 cyl experience.
Even a factory sst60 56 ci will touch a 100hp In apba class form.
It seems to me it takes lots of work to get a v to 2hp/ci or over.
Easy on an omc 3cyl.Last edited by powerabout; 09-25-2017 at 07:16 PM.
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