Mercury in line 6 hop ups

**mrcrsr** · 06-19-2017, 06:21 PM

I know we have some in line 6guys on here, so I want to build one for our viper. I'm starting with an 87 115, adi engine. I already plan on putting hi domes in it. Any other tips?

**thornl01** · 06-19-2017, 06:26 PM

Have the entire rotating assy balanced. Did this years ago round track racing & it's worth every penny.

Have an experienced machine shop check all the ports & match them all to Sport J specs.

Be sure to check the reed block / labyrinth seal areas for wear. When these get loose, these engines are hard to start.

ALWAYS ! replace the inner exhaust plate & gasket, they are prone to leak.

Have heard of some folks who deck the crankcase face then have it line bored to increase compression a little more. (pricey!)

**Capt.Insane-o** · 06-19-2017, 07:05 PM

An 87 115 is already stronger than all it's predecessors. Straight bores, IF you can find an aluminum flywheel, and if you are careful you can stretch out an o ring around the crank to fit in the middle grove of each reed block and it really helps with idle quality.

**mrcrsr** · 06-19-2017, 07:48 PM

Can't I use a v6 flywheel with the hub from the inline?

**Gmcviper** · 06-20-2017, 12:51 AM

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I ported this in a bridgeport. 72' 140. I didn't change the port timing just "squared" it. 2x on the balancing merc made no attempt to balance to these things and they are WAY out.

**mrcrsr** · 06-20-2017, 06:21 AM

I heard that the ports we're wider in some of the 150's. It would be cool to come up with some port dimensions.

**janihei** · 06-30-2017, 04:35 PM

http://www.screamandfly.com/showthre...f-late-inlines

**commrad** · 07-03-2017, 09:55 AM

run 100 low lead av gas so you don't have to back the timing off to keep from burning holes in those new high domes and use Wiseco forged pistons (last I looked they were no longer listed for the I6 but were for the I4). The 115 ADI is a prop rated 1400 ADI which is a 1500 with low dome pistons and a new number because the 1500 at that point was a V6 and they didn't want people to confuse the two engines. There were low dome 1500s later in the production runs. IIRC the port timing is a little more conservative on the 115 to give better low to midrange torque (loose a few rpm but have the torque to pull more pitch for the same effect)

keep in mind these things are under 100ci, Mercury has never been called slow that I know of, the race version was only rated 5 more hp than the first few years of the 1500. HP is a non existent number, it is calculated (torque x rpm divided by 5252). The only way to get more HP is to increase either torque, rpm or both. If you make the ports more aggressive you lose torque but you are able to make it up with rpm (sometimes). the only way to increase torque is to increase compression, as already mentioned, is deck the block BUT you better be ready to run race gas or back the timing off quiet a bit with high domes (a LOT of money for basically no gains since you've had to time it down to keep from burning it up) or increase bore.

Unless you're putting it on a sub 500 pound hull and running a chopper, cleaver etc you're really wasting your time and money. I LOVE my 76 1500 high dome but my 90 ADI is a MUCH more practical motor.

The ceiling for these things is around 175hp gross on race gas IIRC not a lot of gain over a stock 1500 considering they were under rated at 150hp from the factory for a LOT of money and you'll be turning it between 7-8k rpm to get it.

If I were building one I'd square the ports (as mentioned), clean up, radius/ smooth the intake tract, Boysen reeds, forged pistons, go up 1 or two sizes on the mains and as mentioned BALANCE it. Don't forget gapless plugs, I've heard a lot of people say reg plugs melt the pistons. I assume because they protrude into the swirl and cause more of a bang than burn. Run AV gas at no more than 40 to 1, 32 to 1 if you are going to over rev it.

**daveswaves** · 07-03-2017, 07:30 PM

Originally Posted by mrcrsr

Can't I use a v6 flywheel with the hub from the inline?

YEs you can. I have a v6 flywheel on an inline adi hub to give me a 16 amp charging system on my inline. The ring gear teeth are different on the v6, i removed the v6 ring gear and welded on an l6 ring gear.

**W2F a V-King** · 07-03-2017, 10:53 PM

Could a V6 starter me "modded" ( starter drive or mounting differences? )to work on the I6 with the V6 flywheel?

**1954bmw** · 07-04-2017, 09:58 AM

A hundred years ago, a tool maker friend told me about taking the bolt on the reed cage, under the carb out, then you machine the mount for the bolt completely away, the bottom bolt keeps it together as you bolt the crankcase halves together, then the crankcase keeps it together, we even had a custom reamer made (working at GE was great) to open up the reed block holes a few thousanths. Was a great running 135

**Mark75H** · 07-04-2017, 05:48 PM

The amount of misinformation on this thread is amazing.

**1954bmw** · 07-04-2017, 06:29 PM

Originally Posted by Mark75H

The amount of misinformation on this thread is amazing.

Are you referring to my post about removing the bolt in the reed block???? I have posted that elsewhere and no one commented, do you feel that it can't or shouldn't be done??? Would it cause a problem?? I have pictures of it, it worked for me, don't know if it made a difference, did not do a before and after test.

**Dave S** · 07-04-2017, 07:56 PM

Naaa Sam is just commenting on all the stuff that he don't think is right. Your post about the front reed bolt is an old trick' that a racer .... his name was Hansen used to do. I used to mod old L6s just for bay use. I feel lots can be done on the transfer cover. The sharp edges in the crankcase to transfer port block side. The reed blocks from the early 150 have 2 more holes and better reed stops/reed for air flow.