80 inline 6 questions

[Donger]

I have a 83-86 mercury inline 6 cyl. Blew the no.5 piston. I am having all the cyl. bored to 0.020 over and rebuilding the engine. I have been doing research online for good 0.020 pistons, but can only find a couple of websites to supply them. Do any of you have suggestions? I do not know the model/serial number of this motor as it was assembled before i took possesion of if. It was made of several other motors....Also, it is a boost port motor, so i need the boost port pistons( i think they have 2 rings?..)

Also, what is the powerhead rated hp of this motor, i
am. getting conflicted reports of 200 to 235 hp at the crank...

 

[mthieme]

Re: 80 inline 6 questions

The biggest tower Mercury made was a 150 - which predates your motor by an easy decade.
Sounds like real Frankenstein.
If it were mine, I would disassemble it first before spending any money on parts.

 

[Chris1956]

Re: 80 inline 6 questions

Donger, In the eighties the most powerful 6cyl tower made was 115HP. It was nearly identical to the 90HP inline six. A 115HP inline six of that vintage will have 120- 125HP or so at the crank, and about 115HP at the prop.

Power boost pistons come in two keystone ring and three rectangular ring configurations. They are interchangeable.

Make sure the timing is set properly, the link and sync is correct and the carbs are clean, or it will just blow up again. Prop it to run at 5500 RPM at WOT

 

[Faztbullet]

Re: 80 inline 6 questions

Why bore it .020?? Will not .015 clean it up? The only .020"s I know of on the market is the Wiseco piston.(I dont like).If you use the Wiseco add .0005 clearance to bore size to help from cold siezing the pistons.

 

[Donger]

Re: 80 inline 6 questions

It may be bored .020 or .015, depending on the machinist doing the work. He said it may go more than that due to the damage in cyl when the piston blew up. Left gouges in the sleeve, yet it was in the section the rings do not travel. He said run it like it is and it will run as long as a new one would.

mthieme, it is already apart, all parts are good excepth the piston that was damaged and the cyl it blew up in. I decided to do all the cyl over and replaced all the pistons because i want it done right, completely. I want a new motor basically. I am anal about that kind of stuff.

will the repair manual we have state how to set the timing and the synch?

 

[CharlieB]

Re: 80 inline 6 questions

Have you figured out the CAUSE of the blow up?

What's to prevent this from happening again?

 

[Donger]

Re: 80 inline 6 questions

The piston pin gave out. The rod was no damaged, the crank was not damaged. Nothing basically was damaged that i see on takedown except for the piston...weird....???

Picking the block up tomorrow from the machinist, either way getting new pistons all around and new gaskeat set and a new water pump.

Can anyone think of anything else i am missing or overthinking or not thinking of at all????

 

[Droll]

Re: 80 inline 6 questions

The piston pin gave out. The rod was no damaged, the crank was not damaged. Nothing basically was damaged that i see on takedown except for the piston...weird....???
Can anyone think of anything else i am missing or overthinking or not thinking of at all????

You might want to rebuild the carbs too, especially the top carb, just to be on the safe side...
Then you should inspect #5 rod , be sure it's 100% straight and does not have any damage...

As for pistons....Mercury, Sierra, ProMarine are good pistons ( last two with the "Persan" logo inside piston ), have alway heard to stay away from Wiseco in these classic inlines...

Why replace ALL piston ?? if they are within spec they are OK, just replace the rings.
It's alway a good idea to replace rod and main bearings ( at least the ball bearings ) too.
+ The top/bottom crankshaft seals, NOT included in the gasket kit .

As for setup, take a look at this post .

Also, what is the powerhead rated hp of this motor, i
am. getting conflicted reports of 200 to 235 hp at the crank...

Biggest production inline 6 had 155 hp at the crankshaft ( 150XS ), the racing engines ( T2 / T2x ) had 180 > 200 hp at the crankshaft .

Arne Kjetil

 

[Donger]

Re: 80 inline 6 questions

Picked up the block today. He bored it 0.020 over, he said that is what he would do if it were his engine(he is a retired mercury marine engine builder) so i will honor his wishes as he still is contracted to build race motors for people i am not at able to mention. I have found the pistons online for 112.00 dollars and was about to buy them when he told me of a local ditributor of the same if not better pistons. They do not sell to the public.....but if you know him and his company name which is not listed, they will sell to you/me for wholesale price. I will visit them tomorrow and let you all know...

Droll, i will be rebuilding the carbs, i have 2 sets and will rebuild both for fun. As for the rods, i also have 2 sets of good ones minus the one that got knocked around when the pin in the piston decided to break free, thanks for all you guys help and advise in this issue. i will update you soon as possible, i want this project done asap, like next week or so...

 

[Donger]

Re: 80 inline 6 questions

Alright, so.... found the pistons for this motor in 0.020 oversized...they want to know if this motor is for low dome pistons or high dome pistons. I do not know, i do not even know the serial number...I do know the dude i got it from who owned it for 20+ years said it was an 83-85 model... it is not a distributor model, it has the computers and coils. Anyone with any help before i guess at it?

 

[Faztbullet]

Re: 80 inline 6 questions

I build all my customer engines with high domes but reduce the timing 2 degrees and up mains .002 so it can run 87 octane and still have power. Some people swear to use low domes due to fuel but (knock on wood) I aint had one come back in a long time. If your worried about fuel issues use the low dome and stay with standard jets and timing and you will be safe.

 

[Donger]

Re: 80 inline 6 questions

I will run priemium in everything i own so i guess i will get the low domes. What about the restrictors in the fuel bloways? They are small sleeves that are a pinhole size that are tapped into the ports where the gas and air flow, they are very small and black.He said that is where the fuel mixture drains into the cyl. I am missing 2 of them, my engine guy said order them through mercury cause they could cause a bogging on take off problem due to gas buildup in the cyl area while idling, due to excessive drainage ...by the way, with the motor apart i took and ground all the flow edges on the ports smooth and sharp as he showed me for better fuel/flow delivery. But those small sleeves are missing in 2 holes and i heard can cause problems....

Oh, what should i expect in gains for porting the powerhed out? and should i coat it(the bare metal), with anything as fuel and air air rushing over them?

 

[Droll]

Re: 80 inline 6 questions

Alright, so.... found the pistons for this motor in 0.020 oversized...they want to know if this motor is for low dome pistons or high dome pistons.

If it's one of the last inline 6 115 hp engines it came with low dome powerport pistons ( 1" hole in the side of the piston ).

You can however use high dome power port pistons too, could give some extra hp IF you changes the reed block too, BUT it will be more prone to problems if using the wrong fuel and/or something wrong in the setup..

0.020".. the your only choice in pistons are Wisecos...NOT my brand..

I will run priemium in everything i own so i guess i will get the low domes. What about the restrictors in the fuel bloways? They are small sleeves that are a pinhole size that are tapped into the ports where the gas and air flow, they are very small and black.
Oh, what should i expect in gains for porting the powerhed out? and should i coat it(the bare metal), with anything as fuel and air air rushing over them?

Replace the restictors, can and will give you idle problems....

As for ANY port work....IT WILL ONLY GIVE LESS, leave it as it came from the factory, chances are you only damages it's performance.


Arne Kjetil

 

[Donger]

Re: 80 inline 6 questions

Can someone find me the original part number for those restrictors so i can get them coming...please

 

[Faztbullet]

Re: 80 inline 6 questions

Merc part # 66517.... 5 in a pack This is a Merc only part so dont waste you time looking for it aftermarket.

 

[Donger]

Re: 80 inline 6 questions

Thank you. All the shops here in Arkansas can no longer get their hands on these restrictors. I had to order online and they are coming. Now all I need is the overhaul Gasket set and I am set.

 

[Donger]

Re: 80 inline 6 questions

Oh, Droll, my friend and i would like to know what the boost ports exactly for, please.

 

[Droll]

Re: 80 inline 6 questions

Oh, Droll, my friend and i would like to know what the boost ports exactly for, please.

Boost port or as Mercury named them Power Port.....

Extra "grove" in the cylinder wall, it placed between the 2 intake ports .

To get it's advantages, it needs a 1" hole in the piston, power port can be used in a non power port cylinder too, will give better lubrication to those as well ( but NO extra hp ).

Left piston are a LOW dome 3- ring power port piston
Right piston are a HIGH dome 2- ring (Half keystone rings ) power port piston.



Power ports came in 1973 on the 150hp, this was the only difference from the 1972 140 hp engine.
It's main purpose was to improve lubrication and cooling of the pistons, it's side effect was 10 extra hp ....

Power port are used on ( only inline 6 engines listed ):
150 1973 > 1977
140 1978 > 1982
115 1983 > 1988
150xs 1977 > 1978


Arne Kjetil

 

[Donger]

Re: 80 inline 6 questions

will the 1150 overhaul gasket set on this website be for my 84 inline?

And.....did the 84-88 model come with a thermostat? The dude i bought it from said it would run for a while then open the thermo and water would trickle out in drroplets and steam form, i am leary on this as it is a water cooled motor...wtf? i need a straight answer, please

 

[Donger]

Re: 80 inline 6 questions

bump....does it have a thermo? i dont think it does and that may have caused the first engine failure. I did pull up a 1984 motor on youtube and it pissed right away. This guy is saying that it needs to warm up first, then it spitts small amounts of water and steam out of the pisser? what do i do?