TOPIC: Inline inner exhaust baffle improvement?

Hi guys,
The following is a long dissertation of what I have found (some repeated from a year ago post) and what I did as a possible permanent solution to this frequent issue. As background I run a 74 1500 on a vector and 76 1500 XS on a Switzercraft so solving this has been high on my to do list. I run the boats mostly for speed runs so the exhaust gets toasty more than it would cruising with occasional WOT blasts. I have several older inline 6's that I run but not germaine to this issue.
Properly assembled the stock Merc gasket, new baffle, flat block face, torqued correct, Merc epoxy etc. lasts me about three years. I have only looked at the "distributor" years 73 through 77.
There seem to be many theories around why these gaskets fail, most obvious is lack of water, this is not the case here, I run pressure gauges and am religious about watching while at WOT. So I figured there has got to be a basic weakness.
My stream , running like a top suddenly dropped RPM end of last season, I shut down immediately. The culprit turned out to be this gasket failure. I got lucky minor piston scuff on one cylinder, so I got a new stock piston did a hone and ring refresh on the motor so mechanics are good again. I obtained a new inner baffle so to leave nothing to chance.
Keeping in mind the same actions give the same results I wanted to look into possible changes to improve the situation.
I started looking at the water flow from the block base through the block, I found there are two variations in water flow, the earlier blocks ( nuts and bolts on block halves) and later blocks ( only bolts on block halves) supply water to the area under the baffle plate two ways, the earlier blocks are inferior in this regard so I surmise Merc corrected this when they modified the block casting for the " bolts only" style block halves. That said the Stream runs the earlier style block , the XS is the later style block but, both of these developed the leak after time. More on differences in next post.
So back to the earlier style 1500 on the Stream. I was able to remove the inner baffle on the 1500 without ripping the gasket to pieces and it was clear that the gasket was being grilled like a panini. Once it grilled long enough, it got brittle and broke away. I know many think it's the baffle warping and unclamping ( like an overheated 4 stroke cylinder head leads to head gasket failure) and this may happen but, in this case it was clear the gasket baked around the port area. The exposed edges almost look burned from hot exhaust flow too. Keep in mind it's probably a flame coming out of the ports.
I believe the later gaskets are not as good as early ( asbestos based?) ones when it comes to temp resistance.
Materials as good as asbestos are pricey and asbestos is illegal now. I'm sure what is used is " good enough" for most uses but that's not us is it?

Grrrrr can't post pictures to continue thread, Grrrrrrrr, I get the choose image but not the upload dialog box???
Grrrrrrrrr been totally frustrated posting pics on this site, anyone else have trouble with an I pad I have all my photos reduced below max size.
Randy

Randy, if you are below the max size you should be OK, I have run into pic posting problems before though. I would like to see your solution as I have cooked my share of baffle plates too.

Randy, if you are below the max size you should be OK, I have run into pic posting problems before though. I would like to see your solution as I have cooked my share of baffle plates too.

I just tried to post a pic and ran into the same thing.

Well you'll be interested in what I've discovered and done for better or worse. No sense in describing without the ability topmost pictures...

Here is picture showing gasket cooked and crumbled

OK having fun now....To continue I read someone had determined gasket material Merc uses is good to 350 F. I found gasket good to 650F continuous with spikes to 700 F OK in same thickness as stock its flame retardant and compatible with oil, gas, exhaust, water etc. it's made by Garlock and I made a computer file to have gaskets water jet cut to exact shape as Merc gasket. Picture shows stock Merc in black and new one in gray.

Next where the 1500 is earlier nut bolt style case/ block I needed to improve water flow to the inner exhaust water jacket. It was easy to make it similar to the later bolt only case blocks by drilling an existing hole deeper to connect into the block base that gets water right from the pump.

View of drill poking into the base area.... this drill hole has a slight break trough into the cylinder water jacket just below # 6 the later bolt only block cases have more metal cast in to prevent this...but my next post shows the solution on these earlier blocks......




The block base cavity feeds water to two areas: the inner exhaust jacket...and everything else via a larger casting channel leading to the large outer flat water jacket ( the big flat black one) on the outside of the motor, from there it flows into the cylinder area and exits across the top of this same outer waterjacket where it goes down the height of the block in a long narrow water jacket. The water from the inner exhaust water jacket area will exit into this same long narrow water jacket.

.........I pressed in a thin wall Stainless tube to solve this break thru. The break through is small so plenty of hole length on each end for the tube to seal on

Now I've got a better gasket and better water supply....but wait there is more!

So the later blocks have a single hole for the water to exit, this may build pressure as water can't escape as fast as it enters but it does limit flow, flow is what carries the heat away so.....

This shows the hole location on later blocks....it has to be drilled on earlier blocks, it connects through to the long exit waterjacket leading to the mid section where water exits. I put the drill bit in a protective sheath so the drill tip will drill without the drill flutes digging into places I don't want damaged, where drill is angled to get hole right it's hard not to " touch" edges of other areas as can be seen.

To increase flow, I drilled a second hole higher up.
Logic is this: more flow means better cooling so better exit means better flow. Under low pressure, i.e. Lower rpm's the jacket will fill and spill over the top and trickle down to exit out lower hole, as rpm picks up water will start to push out upper hole too. Yes a bit more water flows through this area meaning slightly less in theory goes to the cylinder area but the water pumps push so much volume I have not measured any real reduction in pressure so I believe this area can get more flow without effecting cylinder area cooling.
Oh by the way, this is the only hole you'd need to drill on a later block

By now you've noticed I'm using studs not bolts....these threaded holes are not deep so to maximize thread engagement and not twist stainless bolts under load into aluminum threads I bonded in studs using the Merc recommended epoxy sealer. The studs fully engage the full length of the threads,way more than the bolts do, the epoxy locks them in and seals the threads from any moisture, like Merc intended. I let all this cure before proceeding but to make sure the studs are pulled up to contact the block threads, before cure, I snug a baffle plate in with a very light torque using free spinning nuts. I remove the nuts and baffle after cure and continue assembly. NOTE: clean excess epoxy before placing baffle or it will glue in place!
This way, at final assembly when really torquing down I am not pulling against epoxy trapped between the threads but on metal to metal. This is standard for stud install when using a loctite or in this case epoxy as a thread locker/ sealer.

So now there is a better gasket, better flow and studs for better clamping....still more...

So it occurs to me that it's the real hot exhaust flames impinging on the baffle deflectors that make the baffle incredibly hot, the flames go directly heating it rather than just pass by. I believe that's why the older 135's and 115's are not as susceptible to this failure, the baffle plate does not get blasted the same way. Anyways that's a theory...not sayin it's right. I also think asbestos based gaskets where probably used back then when it was leagal, that is the perfect material to base a gasket on in these situations..again theory.
But, I thought this the case so how do I now seal the waterjacket with " a cooler" layer of metal against the gasket to further minimize temps and burning?
I'll digress for a moment to say at a metal to metal interface there is a temp drop across the joint, not much but bare metal on bare metal is like 80% efficient so picture a hot piece of metal bolted to a cooler piece of metal,
the joint has a hot side and a cooler side because the heat does not transfer well across the joint to get both sides equal in temp. Soooooo...I figured it would be nice to buffer the heat from the baffle from the gasket face while still allowing the baffle to cool...how to do that.....I made this....shown in next post but, here is gasket placed...

And here is what I'll call the buffer plate placed on top of the gasket... Another excersize in generating computer file and water jet cutting.


So this is really what seals against the gasket, it's 1/16 inch thick aluminum...pretty flimsy for clamping a gasket seal so, I the place the baffle on......

This shows baffle on.....

So now the thin buffer piece is clamped down using the baffle plate. The buffer plate has full cooling and very little edge exposed to the exhaust flow flame temps. The baffle takes the exhaust flow hit like always but has a degree of cooling by being heat sunk metal to metal to the buffer plate, so yes the baffle will run a bit hotter but the gasket face will run cooler. I do not believe the baffle will heat to the point of deforming/ melting as it is still cooled through a large metal to metal contact area still regulating it so it really can not get that much hotter than before. In fact it may be better due to the poor cooling flow as originally done. I have this suspicion that there would be localized boiling on the original baffle plate when used alone as the weak water flow could not keep up with the heat input,once boiling starts very little heat would be removed and temps skyrocket locally..burning our poor gasket .....all the while the cylinder side water jacket is just fine......so we don't notice, my theory only.
I put this close up to show the nuts, I used deformed thread and thick flat washers so no sealer locking agent needed for this high heat area. Keep in mind there is some heat sinking of the baffle through the studs, but not a lot but, this heat goes right to the water jacket and would not heat the gasket face so it helps some and does not hurt.

I torqued these in Merc manual order in three stages but final torque value used was higher than manual dictated to counter the drag caused by the deformed threads and studs are more robust to pull against. Manual recommends 150 inch lbs, I used 250 in- lbs which is way safe for a 5/16 fastener. I think Merc went light on torque because of the shallow thread engagement into aluminum ( bad combo) when using bolts. This way gives way better clamping.

OK you are all saying...but wait the baffle is now too high to stack on the outer baffle and outer water jacket cover.......yes you are right except I have an easy solution. Pictured are two gaskets and a shim (the three that look very similar) used under the outer baffle, so the shim and the second gasket are slightly thicker (.075 in total to be safe) than the buffer plate (.062 in ) I used under the inner baffle. Yes, to make the shim it was back to the computer to make a file and another water jet cutting job but it fits as good as the gaskets do.
This "shim" also blocks some un needed holes on the earlier blocks rendered un needed with the hole mods. It is fine on the newer style so no problems there.
The outer jacket goes on with its gasket as usual.
Now one more thing...the control cable guide that bolts to the block needs to be spaced out too to clear the outer cover now raised the .075 from the extra shim/ gasket. I used a .100 thick washer at each bolt hole (3 places) to do this. Shift linkage does not notice this minor difference in geometry this introduces.

So far so good !

Very good!!

Awesome write-up Randy, thank you for sharing!

Thanks Randy, I love the stud idea rather than the bolts. Your write up is right on the money. Did you make extra gaskets for sale??

I had 6 sets of everything cut. I sent the good doc a set for free so he could check it out. After all the help he gives here that's the least I could do whether he uses it or not. I have all the files and more material too.
None of this was cheap relative to buying a stock gasket, in the end making only 6 sets the gaskets were like 65 a pop plus material which was around 20 per gasket. The cost on the other pieces was mostly the cutting charge where the sheet aluminum was far less expensive. Of course nothing for all the time it took me to make the files of the exact size and shape, it took me a few trial cuts to get them perfect. I got lucky in the company I used to water jet was very prompt and willing to do single pieces to speed the process up.
Dave PM your phone number My thought all along was there would be others wanting at least the improved gasket, but realize that motor budgets and use vary. We should talk.
That said although in theory this is all "better" I wanted to get some hours on it first. I have about 20 hours of run time logged so far. I'd hate for some unforeseen flaw to rear its head and have others sucked in. That said Merc definitely had a weakness in this area.
Randy

I'm following your write up very closely- awesome work has it passed your R&D? - I think it may be whats wrong with my motor. I just bought a 1976 Hydrostream Viper with a 1500 Mercury. I bought it out of state and when I got home and tried to use it - it was bogging when trying to plane. I didn't run it very long at all, but it did eventually plane off and run well once it got past the initial plane off. What I noticed when I got home was that cylinder 3 had a creamy buildup on the plug all others looked good - on the rich side. Since the motor has even compression across the board i'm hoping that my water intrusion is occurring thru the exhaust baffle gasket like you writeup seems to point out an area of weakness. Its a fresh water motor so I'd hope the block isn't garbage. Can this be done with the powerhead on - I just don't want to open up a can of worms by pulling the powerhead...if my issue was the exhaust gaskets I'd be very interested in your gasket/plate setup.


This motor is a little before my time - I'm more familiar with the V6 motors. Before I found the problem cylinder I was thinking that the synchronization was off - it seems that the ignition goes to full advance before the butterflys even begin to open... My other motors have more of a proportional relationship. Is that normal for these inlines?
I'd appreciate any pointers you had in troubleshooting the source of my issue.

Some info to note:
Work done in the last year with receipts (not limited to):
Fuel pump rebuilt
CDI rectifier
CDI stator
New fuel line
New water pump

Wow this thread has been dead for a while....as an update, I ran the 1500 all summer with the mods and all is well. I am doing the same to a 1150 I am building for a Glastron GT 160 project right now. It is a 76 motor so I only needed to drill that second upper hole and bolt it all back together with the improved parts.
Nice combo you have, my experiece with the Vector and Hydrostreams in general is if your original balsa core has not been replaced it's a near impossibility that it's OK. I hope this has been done or was in your plans when purchased...it's an ugly job. Don't want to sound like a Debbie Downer but it is the Achilles heel of these....all worth it if it's a special boat to ya! On a lighter note I found a 24 pitch Laser works as good as any prop I tested and I tested a lot of them, it comes on plane much easier than an over the hub exhaust chopper, the fastest I used (Only by half mph) was a cleaver but ridiculous excersize to get boat on plane.
So to address your other questions, yes, I'd wager it's your inner exhaust water jacket. Practically speaking you should remove the powerhead, the lower cowl is pretty much in the way even when it is unattached and wiggled out of the way as much as possible. Once you can look in through the port areas check for piston scuffing on the exhaust side in your case particularly #3. Frequently that happens when the leaking water turns to steam it'll leave a skid mark of aluminum on the cylinder wall, and a ring or two might get stuck in its groove
( try the spring test to see if you can push the ring in and watch it spring out) this skid has to be removed and the rings and piston cleaned up meaning a more involved tear down, generally it's just a clean up and no new parts would be needed. To reassemble the inline takes special ring compressors or a lot of finagling with thin sheet stock and zip ties....I've done both ways.
As far as power head removal: It's not that bad to do, best if you have the lift ring that threads into the flywheel and a hoist of some kind. Remove the cowl supports upper and rear, leave the front one on the lower cowl but loosen the two lower bolts.
You need to disconnect the three distributor wires from the switch box, the electric wire to the choke solenoid and the two stator wires from the juction buss on the side of the block. Only the fuel line, the control cables, and the shift cable slider need to be undone, pull off the pee hose from the back of the block, then unscrew the lower nuts on the powerhead studs (8) and the PH will lift right off. The big side water jacket cover bolts should come out OK but, if meeting resistance heat the bolt head with a MAPP torch to help loosen..... breaking bolts is a pain to fix as drilling them out and helicoiling is easy to mess up till you have done a few.
The leaking inner water jacket bolts are epoxied in so, generally you are not fighting corrosion as the epoxy seals the threads but, heat is needed to soften the epoxy up, same thing as above heat the bolt head...real hot...for a while...be patient with heating, I set a 3 minute timer they will come right out. These are real bad if you break one, the metal is all thin around the tapped holes, scary to drill out.
I find gasket cleaning the most tedious, I soften them up with the goo made to deboned silicone, you can get that at the depot or lowes or try automotive gasket remover, it takes time to work so brush it on in eleven and attack in the AM. I get right down to metal without gouging particularly the inner cover surfaces where leak originates from.
I'll suggest it's the best time now to split the block and reseal the parting line and replace the crank upper and lower seals, the lower bearing cap has two seals opposing each other and don't live a good life where they are located so best to replace where they are aged. The motor will never run right if the seals fail. Also the lower ball bearing located in the lower cap frequently develops play and wear, it is a light press onto the crank. None of this is pricey it just takes time. I would not do this without a manual and the parts list as then you'll see everything clearly both are easy to find on EBay, Merc manuals are best not Clymer.
As far as your distributor and carb opening, there is a procedure to sync that but briefly the distributor does rotate before throttle blades move then the distributor hits a stop and the throttle blades will continue to open, there is a detailed procedure on this. It seems complicated the first time but, basiclly you are adjusting at three spots, the timing when distributor starts to open the carbs, the total timing and finally making sure when you move to WOT using the helm control that the carbs themselves are not the throttle stop.
Keep asking questions, if you are like me the weather is starting to get cool so the powerhead work is perfect winter work!

Just a note on the lower end cap seals, they should be installed with lips facing down, same as the top. They should not be installed with the lips facing each other.

That is 100% correct both go same way lips down, sorry about my misinstruction above. Duh, me bad, I do these in my sleep I guess I needed more coffee prior to writing above!!!
Randy

That is really good news Randy! I am currently in the process of shifting gears from summer repairs to winter rebuilding.
I'm looking forward to doing your modifications to one of my beasts.
doc

Thanks very much for the reply. I do a lot of my own work - head gaskets, rebuild carbs,timing, link and synch, etc. but tearing down a motor I have not done. I do have a lifting ring for V6 merc outboards and a hoist I guess I can do it I would just be completely f'd if I broke a bolt lol. I bought this boat because of its cosmetic condition - beautiful gel coat and soft original interior. Yes the core is surely in need of being done after 40 years. I've done a core job before and this should be easier being that the boat is smaller. I'm definitely a little turned off that this is what I need to deal with because I prob paid too much for this boat but I figured it was a turn key package that needed a core... now it needs a motor overhaul. I've been watching a lot of youtube videos to familiarize myself with these motors - I've heard the Dr. Frankenmerc name get dropped a bit so I appreciate any info you all can contribute. I'll let you know what I end up doing soon. For now I just fogged the cylinders with oil and spun the motor to pickle it...BTW what rpm are these motors happy turning? I see Merc calls for 5500-5800 but I was curious what the realworld users say.
Thanks!

A 1500 would be happy to turn 6000 rpm all day long.

For some off-season inspiration, take a look at this awesome video of Conrad's Carlson Contender powered by a 1500XS: