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Hot rod 9.9 build up

faztbullet said:
You can cut the crossover slot in the 83 model intake
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Was thinking of doing that when I port match the old intake. The 83 is my runner for now If I tear that one apart and don't repair before spring, my wife will be none too happy. When the Bluegills bite one best not get in the way!
 
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Well just an update on on the build. I did some intake work based on my searching. Knife edged the divider in the carb flange area. Although I have read that some have all but removed this divider.
20210210_193221.jpg 20210210_193227.jpg
I have a few voids that I want to fill with weld next time I break out the TIG. I lined up the reed plate with the intake, then installed 3 dowel pins so when I port matched the two they would line up perfect. Then got to comparing the three generations of intakes, I noticed the last two did not have the the plenum dividers at the end. Possible they didn't do enough to justify the extra in the mold. I decided to try something similar to what large ships have. The bulb on the bow to split the water. I ground the same on my intake. If it turns to be a fail no harm no fowl, but thought I would try it.
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I have started to clean up the small half of the crankcase of rough and square corners ever so lightly. And the same to the block half. Some light transfer port ramping and possible squaring up the intake and exhaust, not raising them just opening them in the corners. OMC drilled 5/8" dia holes for ports, I am thinking a 1/2" end mill to open the corners a tad, but not too much. I bought a bag of emery cloth cartridge rolls for my sanding.

Measured the bores and they are 2.189 - 2.1875 so they seem round yet, and there is factory cross hatch in them, so that seems a good indicator. Pistons seem wonky. They measure round at the ring end for both, but on the bottom skirt one is oval side ways and the other is oval top to bottom. Guessing It got hot a few times maybe? I see the OMC supply is drying up. I will try for those. If not I will go Wiseco. I will post more pictures next week when I get the work done.
 
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 <span style="color: rgb(0, 0, 0); background-color: rgb(250, 250, 250);"> factory cross hatch in them, so that seems a good indicator</span> 
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<br>Sorry but this means absolute nothing..cylinders can be out of spec and still have crosshatch
 
faztbullet said:
Sorry but this means absolute nothing..cylinders can be out of spec and still have crosshatch
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Yep, I know that just having the factory crosshatch in the cylinder isn't the only indicator. I'm going to contact my engine machinist today and see what his thoughts on it. My only thought was still seeing the factory cross that means that they aren't tapered out at first glance. I did measure these at 3 locations and 2 measurements per location, 90deg from each other. With a Mic not a caliper. Everything I've read so far indicates that my cylinders are still within spec to put at least new rings in them if not just put new pistons in them. I have it this far apart I figured I might as well. It seems weird that one is oval one way and the second is oval 90 deg to the first. I know they come with a slight oval from factory for expansion and such. I didn't hear the "trolling piston rattle" like my 6hp Johnson does, but for 100 bucks a hole that is cheap insurance for a longer life.
 
If you want maximum power out of the many hours of effort , you should not be putting new rings on old pistons.-----That would be a huge mistake.
 
racerone said:
If you want maximum power out of the many hours of effort , you should not be putting new rings on old pistons.-----That would be a huge mistake.
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Yep, my plan has new pistons in the budget. All new bearings as well, wrist, rod and cranks. They look good, but now is the easiest time to change.

Pistons are a tie for me between OMC and Wiseco. I have had great dirt bike results from Wiseco. I looked into WSM pistons, but read poor results ffom them. Thoughts??:confused:
 
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Quick question on crankshafts. I saw that there is two item numbers listed for my 75 9.9. The earlier p/n 0318678 and the later p/n 0336754. Does anyone know the difference between the two? Mine has some surface marks, kinda brown in color, guessing from it running lean. I see they are both around 100 bucks. And being I am putting new slugs and bearings down the bore, cheaping on a possible compromised crank is no Bueno.
 
BRUPP79 said:
Quick question on crankshafts. I saw that there is two item numbers listed for my 75 9.9. The earlier p/n 0318678 and the later p/n 0336754. Does anyone know the difference between the two? Mine has some surface marks, kinda brown in color, guessing from it running lean. I see they are both around 100 bucks. And being I am putting new slugs and bearings down the bore, cheaping on a possible compromised crank is no Bueno.
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After 76' the crank no longer needs to accept the point cam...maybe that's it?
 
OK, here is a shot of the crank. no ridge felt on crank. I have to get some steel wool or some 1000 grit wet/dry paper. Will try to polish on the lathe. Will measure before and after just to be safe.
CRANK.jpeg
 
Been sidetracked with a few other projects. But got a few things done. I will try to post pictures tonight.
1) I ended up having to lightly shave the head and the block. Both head and block were cupped opposite of each other. I set them up in a mill, leveled them as best I could. It required .015" off each side to get the flat. The OEM squish band is still clearly there, but I will check with clay when I get that far.
2) I squared the in & out ports a tad. The OEM were 5/8 round, I used a 1/2 end mill to the roof corners, but did not raise the height so port timing stayed the same.
3) Removed any casting edges, lightly rounded/ smoothed the transition from crankcase into transfer port area.
4) Ramped the transfer to intake port area to start the flow direction change earlier/easier per a few members suggestion. Similar to this picture.
64445-b665efd8d79e53c59e442e0cf69e2edf.jpg

Thats it for now, pictures tonight. Thanks fof the tips thus far everyone!
 
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Grind back the liner side of the transfer port back..or up..so 1/4inch of piston skirt shows when its down...like the "D" cut..but without trimming the piston. Since the piston skirt thrust on power stroke is on the exhaust side there will be no unwanted issues from this mod...except your smile might be permanent. Use 518 with no gasket on the intake cover to gain back some case compression.

This mod was the best mod I did on my '76 by far.
 
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Well, I ordered up parts finally. I hope to have this puppy back a running soon. OUCH! $750 and change to rebuild it! I guess I coulda saved some, but figured all new bearings is great insurance, especially if stuck in the middle of a lake! OMC parts the whole way except Boyeson Reeds. Would have gone Wiseco, but they didn't supply the wrist pin bearing, and the OMC one is not available. I found the size for size bearing thfu my local supplier, but it doesn't have thd oil hole in the outer race. Figured it's there for a reason. I though to mysrlf, it is almost cheaper to redo a SBC 350!:rolleyes:
 
I pushed out the older, smaller style wrist bearing out of the rod and used the later year with a larger pin on mine....needles run on the rod. That might be the availablity issue with the pistons. Try an '85 or so for the larger pin style..now that ya have ordered stuff...
 
Update on this project. All of my parts are here. I have chatted with a few guys that build these for racing, they all mention Boyesen reeds which I bought. It was mentioned to port match the reed plate to oval cutout on the main reed so you gain flow. Also to bevel contour the back side of the plate to ease the path. If these don't work out a reed plate is cheap. The last of the main change I want to do is adding the cone style tuner. One of the build shops I chatted with mentioned "try to eliminate any obstruction in the exhaust path to a reasonable degree". I got to looking at the two side by side and the cone has a noticeably different & smaller opening compared to the old square one, which is more funnel like. Question has anyone sought to make a "runner" to fit in there some how to make the flow a bit more clean? So the path blends from block to tuner port? Kind of a partial chunk of an elbow of sorts, if that makes sense. I imagine it would fit snugly in the void between the block and pipe. I took as best pictures as I could. Anyways, OMC didn't see the need to do it, and it produced power enough for the myriads of 15hp's they made. But the mind of a tinkerer never shuts off, UUGGHHH.... Thanks again for being patient with my incessant questions:rolleyes::rolleyes:
pipess.jpg just a side by side

exhaust 11.jpg looking down inside with the cone bolted up

exhaust 22.jpg another of the cone bolted up, you can see the huge mismatch.

exhaust 33.jpg this is the older square style
 
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For now it is going on a 12 ft lund car-topper. So this build will be a bit overkill. Over kill, but fun to drive! But I have a 14 ft it can go on aswell. Most of why I am building is just to see what the max one could safely squeeze out of this engine platform. But I have always liked looking for the not so obvious things to upgrade if it is possible and productive. I dunno, maybe I am off center too much sometimes:cool::cool::rolleyes::rolleyes:
 
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What prop do you plan on using? I just lake tested my stock 1975 9.9 rebuild. It has a 9.5x10 3 blade aluminum prop. On a 12’ aluminum V-hull boat it runs about 16 MPH GPS +/- depending on wind direction.
 
I think depending on what I'm using it for at the time I guess. Right now I've got the same prop as you do, 9 1/2x10 3 blade, which it seems to work real well as an all-around prop. But I did find a 2 blade prop I believe is a 9x10 also that I might try just for cruising prop for blasting around the Lakes. But I've also been looking at a 9 1/4 by 9 or 8, 4 blade prop, which if I understand it right will give me better mid-range get the boat on plane with a heavy load for camping and such. Although I would lose some of the top end speed with an empty boat what I'd have to worry about over speeding the motor. But normally for camping that wouldn't be a big deal I just don't want to be plowing water.
 
will give me better mid-range get the boat on plane with a heavy load for camping and such.
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Whoa!!! STOP!!!!...All the mods you are doing enhance top end WOT performance. Some of the intake mods may hurt the low end performance and load carrying. The mods you ae doing are for a go fast motor on a lite load hull turning extra RPM
 
faztbullet said:
Whoa!!! STOP!!!!...All the mods you are doing enhance top end WOT performance. Some of the intake mods may hurt the low end performance and load carrying. The mods you ae doing are for a go fast motor on a lite load hull turning extra RPM
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Oops, I see I missed alot words in my thought process. I guess my line of though should have come out as the following: From what I have read and trying to figure is a four blade prop in a 8 - 9 pitch may give me better mid-range boat speed and get up on plane easier with a heavy load, while allowing the engine to run in its tuned rpm range. Kinda like running a heavy pick up truck in a lower gear, that has a race cam and single plane intake to move a heavy load. Sorry for the 2 vs 4 cycle compare. I know they aren't exactly the same. I do know that once the 350lbs cargo is shed from the boat I will run out of prop and go into over speed. But the swap a prop at camp is easy enough if I want.

Hope I haven't misunderstood the prop theory. If so it isn't the end of the world as I have a stock 9.9 that was gotten cheap on auction. Guess I will have a grocery getter and a weekend racer for this boat.
 
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Quick question for everyone. To those that have converted exhaust tuners to the cone style, do you route the shorter copper water discharge line out the spit hole in the back and let the excess water spill the the inside of the midsection? Or do you route the copper line as stated, then block the rest of the OEM water spill area off (shown in picture in green marker approx.)?
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It appears that allot of water will leak past the area in red down into the midsection. Is this a designed thing or something that was changed in the engine casting when the cone tuner came about?
Inked20210426_151722_LIe.jpg

I do believe I read about this in past posts, what people refer to as dry stacking the exhaust? I will continue searching.
Thanks to all thus far! I have to fab up a 3 holed plate to fit at the bottom of the mid section to copy what OMC did. Used to bounce the exhaust pulse wave back when using the cone tuner. Motor is getting close!!!:cool:
 
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Well I did some research and digging and will install without drystacking. From what I read doing that mod does help a smidge at wot racing. There was also some talk of scorched water pumps and over heated prop bearing hubs.
 
Are you getting close to firing up the beast? I wanna see a video of your boat flying with only the prop in the water :)
 
I hope to soon. Spring has brought warmer temps and landscaping projects, as well as a sliding screen door project I put off for 10 years! I hope maybe tonight I can get some time:cool: I am excited to see what a bit of tinkering can do!
 
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