1979 6 Cylinder 90 HP

[flyfish2743]

I am currently rebuilding a 90 hp in line 6 2 stroke 3 carb from 1979. I have it stripped down to the powerhead but am waiting for my flywheel puller. I have about 8 or so bolts that I have managed to strip the heads off of. I tried to back them out with and extractor but no luck.

After totally dissembling the powerhead I am planning to have it cleaned at a machine shop and to have the bolts removed or tapped for new bolts.

Is this the best approach? How much do you think it will cost?

Other than the electrical the motor seems to be in decent shape. It is worth rebuilding considering I am looking for a project for the next year or so?

Thanks for your help.

 

[hamit59]

Re: 1979 6 Cylinder 90 HP

Serial number would be helpful to look up to see what parts are still around for it.
As for the bolts if your not setup with a machine shop and have tried everything you can to take out the bolts then. I would take to the machinist.There is no telling what they will charge, most go by machine time.and that can run from $35 per hour to $75 per hour. You don't have to be a machinist to remove them, if you can drill straight holes. Always remember, most of the holes will be blind. Don't drill too far and always drill them centered. Start will a small drill and step up until you can get it to break free with an easy out or you get to the tap drill. After you reach the tap drill with lots of oil rethread the bolt hole. With most bolts should be stainless steel, I would use cobalt drills with a steady flow cooling oil. Bolts should cut flush with the block and filed flat.use a center punch, punch a center. Use a center drill to start the extraction.you can pm me if you have any other questions

Hamit
BT1 USN ret

 

[flyfish2743]

Re: 1979 6 Cylinder 90 HP

Hamit,

Thanks for replying. I looked and the serial number is 5299872. After
taking apart most of the outboard, it looks as if it is in decent
shape. The gears show very little wear and tear. The engine turns over
very smooth with just the spin of the flywheel. I am waiting for a
flywheel puller to come in the mail to see what the power head looks
like on the inside.

As for the broken bolts, I do have a nice drill press that I can use
to slowly drill out all of the bad bolts and then re-tap the threads.

However, all the electrical needs to be totally replaced. Everything
was burned up!
This is the distributor-less ignition system. It is the type with the
power trim pump/motor assembly mounted in the boat.

The serial number on the engine is 5299872. I am wanting to say I,
"have rebuilt a motor" and thought this one would be fun, it was given
to me for free, and it is just the size my boat needs.

What are your thoughts on side mount steering verses front mount
steering? I believe this motor will only use side mount and did not
know if the type of steering was enough to sway a person one way or
another when considering rebuilding a motor.

Thanks for your time.

 

[flyfish2743]

Re: 1979 6 Cylinder 90 HP

Does anyone know if I can mount a Teleflex front mount hydraulic steering onto this motor? Or would I have to use a side mount? I would prefer to use the front mount?

 

[daveswaves]

Re: 1979 6 Cylinder 90 HP

A couple of things you should know about the inlines; they are not easy to rebuild, having said that you will have a nice motor when you are done. All parts are still available either from the dealer or online at various sites. You will need special tools to re assemble the pistons into the block as all 6 must be installed at the same time. Plan to have a helper and be very patient. If you break a ring during the process you have to start over.
There is no removeable head so if the block needs to be bored it is more expensive than conventional engines. There are pistons and rings available up to 30 thou over, no problem. Gasket sets are available on line and are a better deal than buying individual gaskets. Complete rebuilt powerheads are available also and are fairly priced, this is not a simple rebuild.

You should be able to drill out your own broken bolts. Before you break any more, try tightening them first before you remove them. Machine shops are expensive, another thing that may work is welding a new bolt on top of the broken bolt, the heat of the welding will break the corrosion bond and you will have a fresh try at removing the bolt.

 

[flyfish2743]

Re: 1979 6 Cylinder 90 HP

This is very helpful info. You mentioned special tools for the pistons. What kind are you talking about? I did contact a machine shop to have them quote a price on having a "Hot Tank" bath or having the powerhead cleaned with a jet sprayer and the cost to remove the bolts. I told them I would swing it by after I pulled the flywheel so they could quote me a price. As for welding a head on the bolt, some are very flush and I do not own a welder.

I ordered a fly wheel puller on ebay. Is it an easy task to pull the flywheel?

Thanks for all the input.

 

[robaru]

Re: 1979 6 Cylinder 90 HP

With the flywheel puller, it should be no problem pulling the flywheel. I recently rebuilt a 1978 1400. I also broke off some of the bolts while removing some plate on the exhaust side. I took mine to a machine shop and they were able to get them out, but did break one part of the aluminum casting in one area. They had a guy fix the break, machined it smooth and I've run it for the last 2 years. Putting the pistons back in the holes was definitely a 2 person job. I do have a parts motor that is a 1979 1400 that has the distributerless ignition if you need some electrical parts.

 

[flyfish2743]

Re: 1979 6 Cylinder 90 HP

Does anyone know if the Mercury Mariner 1979 1400 electrical system will work with the 90 HP from the same year?

Looking at the service manual it states on the cover 75 through 150 and specifically has the 140 in this lineup. However, the parts manual that the supplier sent me when I gave them the motor?s serial number states 115 on the cover.

Please advise.....

 

[hamit59]

Re: 1979 6 Cylinder 90 HP

Fly,
You'll have to check the part numbers to know for sure.My thinking it should
But Merc did do some strange things like change the coils for no reason (80's model). So you'll have to go part by part to see for sure.

 

[flyfish2743]

Re: 1979 6 Cylinder 90 HP

If a person is into the powerhead and they have the crankshaft out, is it always recommended to replace the rings?

 

[robaru]

Re: 1979 6 Cylinder 90 HP

I suppose it depends. If the motor was recently rebuilt and a compression test shows good numbers, then it may not be necessary. But if the motor has been setting awhile and not run, I would. A factory manual is a great help in deciding what to replace or not when you break it down that far.

 

[flyfish2743]

Re: 1979 6 Cylinder 90 HP

It has been a couple of years since it ran last. I saw online that the ring kit is only around 50 bucks so it looks to be worth it.

As for the factory manual, I purchased on along with the parts list. Very helpful.

do you know of a good place to get good used or new electrical parts for this vintage?

If anyone in the DFW or Oklahoma City area that has an old merc 90 through 140 HP from around 1979 that is in the way let me know. I'm looking to find some old parts that still have some life in them. :redface: