70 HP Force Rebuild

brianq

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Jul 15, 2012
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At the advice of Jerry I am starting a new thread which will cover the rebuild of my 1992 70 Hp force.

Background:
It would not start found it had low compression in two cylinders, I replaced the head gasket which was damaged but it didn't help, so I decided to take it apart and find out why. I took it all apart and found two pistons have cracked ring lands. Last week I took the block to a local Machine shop to have the cylinders honed. I hope to pick it up this week. I haven't ordered pistons and rings yet because there were several different sizes so I hope the machinist will tell me which to order. Last summer I replaced the floor and foam in this boat so I already have a good amount of money into this boat. I took a lot of pictures and made notes so I am eager to start the rebuild. Anyone can take bolts out it will be putting everything back together that should be the real challenge.

Me:
I am a civil engineer and I have a construction business on the side. I am very handy but I know NOTHING about motors. I have already learned a TON from this site and look forward to learning even more. I found a few youtube videos and I have the Seloc book for this motor. Please bare with my tons of questions and not always using the correct technical terms.

Goals:
Repair the motor, paint the hull and add a depth finder and switch panel. Time permitting I would like to replace the upholstery.

It was terrible not having a boat all summer, I am dying to get back on the water.

Here is a link to my diagnosis efforts:

http://forums.iboats.com/forum/engi...rds/10229274-1992-force-70hp-wont-start/page3
 

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jerryjerry05

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Pic #2 those lines in the bottom of the hole.
They look pretty deep???
​The guy doing the hone should tell you if t needs a re-bore??

​Until you re-assemble? Spray all the parts with WD or any spray lube.
Stop the rust from getting worse.
I use spray, White Lithium Grease.
You can get it at any place that sells oil.
​The bearings need to be taken apart and the surfaces cleaned.
 

gm280

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A couple of issues. Usually a machine shop will mic (measure the bores) and then tell you what size pistons you have to get knowing what they have to bore to to clean up any issues. But they usually wait until you provide the pistons so they can mic them and then bore and hone to the precise size for each piston and mark each piston to the bore hole it goes in to. At least that's how I've done it many times before. I was wondering if you had the machine shop mic the journals on the crank as well. Looks like it could use a polishing as well. If you are seriously going to rebuild this engine, then make certain everything is within spec. Otherwise you are wasting your money and time. That said, I think it will come out really well. Keep posting pictures and you progress. JMHO
 

jerryjerry05

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The shop should tell you if it needs to be bored out and how much they need to cut.
The usual cut is around .020 But from the pics, yours might be less?
If so then you'll need to buy pistons and take them to the machine shop so they can cut the holes to the right size.

You'll need special tools to install factory pistons.
​The assembly is tricky and the tool makes it easier.

Wiseco Piston makes replacements for your motor. MUCH Easier!!
They start at .010 and go up to .040 over.
They include rings but need the wrist pin kit to complete the job.
Wiseco rings WON'T fit other pistons.

Piston and kit $140 each.

E-bay has piston kits cheaper too.

Post pics of the pistons after they are cleaned up.
​ANY!!! scoring on the skirts = trash.

​If the skirts and top are ok?
I used Powertune/Mercury or Engine Tuner/OMC to remove the carbon in the ring grooves.
​A broken ring works well to clean the grooves.
 
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brianq

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Thanks for all the info.

I called the shop he hasn't looked at it yet, should be tomorrow. For now he is just doing a hone but he will inspect if it needs more, the cylinders felt very smooth, I think the picture makes it look like they were damaged. I posted a few more pics. Did some googling to find what journals are and I am going to bring the crankshaft to the shop and have it checked out. I will also speak to him about bringing the pistons and having the cylinders sized to them.

Are the bearings under a collar on the crank shaft?

My plan is to purchase 3 new Wiseco pistons.
 

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brianq

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I took a closer look at the crank shaft. The Journeys are dirty but very smooth. The ball bearing moves well (near taper) , one of the middle bearings is very dry and doesnt move smoothly, one moved well, I will try and clean. The main bearing shows rust and doesnt move that smoothly. The taper is very concerning its super rough and according to Seloc I used the wrong puller so I have to assume I caused this. I used an outside puller which the book specifically says not to. I attached a picture of it.

Is it worth doing anything else with this crank shaft? If its shot prob not worth having machinist measure. According to Seloc this part cant be machined due to sealing and hardening.

If shot anyone know the best way to find a replacement? I checked ebay and the prices range from 49-200 but all of the tapers look rough?

http://www.ebay.com/itm/FA85018-2-F...ash=item1eb7b02dcb:g:3EIAAOSwFdtXzsTM&vxp=mtr
 

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jerryjerry05

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First off only believe 1/2 of what's in the Seloc book.
​I've been using a 3 jaw puller for 30+ years.

The taper can be cleaned/sanded and used.60g paper and cut it in 1in strips.

​The rusty journal, clean it up. Unless it's got pits and ridges it's probably usable?

Pic#3 remove the wire keeper and break the bearing down.
​I bet the surface cleans up and you can use it.
​#5 Unless there are big holes and ridges it can be used.

​Take it apart and use strips of sandpaper 200g or finer.

​If you don't put some oil or spray grease, something the rust is gonna get worse.

​All in all I'd say the crank is usable.
 

gm280

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I too don't think your crank is useless. I can easily see that cleaned up and run well again. But you have to remove everything and then clean all the dirt and debris off to see what is there. And like jjo5 stated, you have to use some oil or something to keep it from rusting again until you reinstall it. Just clean everything up and coat with a good oil or even WD40. You may need some new bearings if yours are rusted, but other then that, you are probably good to go. If you want to clean up the stained journals, use some wet/dry 400 or 600 grit paper cut into strips to fit in the areas and polish them clean.

Post some pictures of the pistons. You said you are going to replace some. Let's see what they look like as well.

Oh, BTY, that crank at EBay looks good as well. JMHO
 

brianq

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Glad to hear the the crank shaft is salvageable restoration is on my list for this weekend. The machine shop is two weeks behind so today I called and asked the guy to measure the cylinders so I can order pistons and rings. He said it was 3.750 which wiseco lists as "standard". I explained to him that you guys advised I order them and give him so he can match. He explained that since he is only honing that wouldn't be necessary since we aren't going larger.

I have attached picture of the damage to each cylinder in order. 1 & 2 have ring lands missing, number 3 is in good shape. I am replacing all 3 since the whole thing is taken apart.

Had an issue today. Got home from work and the big tupperware tub I have everything in had blown open in a wind storm today. I live in a small cottage across the street from the beach so I keep everything in tubs outside but the wind and sand can blow pretty hard here. Rain and sand got in seems 2 of the zip lock bags were open. One had the carb and the other i believe is the reed plate? Its everything behind the carb cant find it in the book. Picture 4. I took the reed plate cartridges/ screens? and sprayed them down with penetrating oil in a zip lock bag as to prevent rusting and not have my house stink. All have fresh water and fine sand on them. Not sure how to clean. Carb I will use carb cleaner and pressured air. The reed plate stuff Im not sure. A friend of mine is a machinist waiting to hear from him how they decontaminate new parts. An annoying set back for sure.
 

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jerryjerry05

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For normal dirt: Dawn dish soap.
​Water hose and a spray bottle with a mix of 50/50 dawn and water.

​Tougher dirt and heavy grease: I use Shout laundry stain treater.
​I use it to clean my hands too.
Use a compressor and blow dry the parts.

Once it's clean and dry.
​If your not gonna use it that day I'd spray with WD or a protectant spray.
For long time storage I use a White Lithium spray.(even use it on my hedge snippers)
Don't use WL on the inside of the carb.

You don't want to use a "penetrating oil" unless the screws need to come out.
WD isn't really a penetrating oil like PB Blaster.
​The name WD-40 is water displacing 40 is the last formula they tried.

​Remember what you spray in the carb or the reeds the gas will have to cut through it and eventually burn it.
Possibly make it hard to start???


​On reassembling the crank and bearings: Use an bearing assembly grease.
It's designed to dissipate quickly when the fuel starts to go through the system.
​OMC grease is on e-bay 171114954142 $10.50
​Regular grease won't melt and can cause damage.

​Do use an oil on the rings and the cyl. walls.
Don't drown it. Just enough to lube.
 

brianq

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Thanks for the info I will clean all parts this week with Shout and hopefully remove all sand residue followed by compressed air and WD40. I ordered the bearing assembly grease, what is the best way to clean those bearings? The dawn and water mixture?

Looks like all parts should be here friday, I hope the machine shop does their work this week (they are two weeks behind already). If all works out I hope to start rebuild saturday. The striped bass arrived yesterday, my neighbor caught 12, I was away in New York, figures right?! This will slow progress but if the bass are hitting i can cope!
 

jerryjerry05

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Yup Dawn and water and WD saves a lot of parts and work.

It sounds like you should go with the neighbor??

Change your profile and add a signature with your location.
 

brianq

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Quick update:

Pistons, rings, wrist pin kit and fuel pump rebuild kit have all arrived. The fuel pump rebuild kit was the wrong one so thats going back I ordered the correct one. I seem to have a different pump then everyone I have seen online its a figure 8 shape as opposed to a square. Cant seem to find any videos rebuilding that one.

Called the machine shop, he still hasnt touched the cylinders so I asked to pick it up. He said it will be ready tomorrow, we shall see. The week I dropped it off he said hed have it at the end of the week. Hope to start working Saturday after a little sunrise surfcasting, still havent landed a striper.

The bearing assembly grease hasnt arrived, is that something I can purchase at West marine? I have some time this weekend I would like to get moving on this.
 

jerryjerry05

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The rebuild on the pump: it's usually just the diaphragm and the gasket.
​I've only seen one valve go bad , ever!
And it was still working?????
​I was replacing the diaphragm and the valve just fell apart and came out in pieces.
​You pump is what Chrysler/Force used up until the early 90's then they went to the square Mercury.

​You can get the assy.grease at any BRP/ OMC/ Johnson dealer..

I'm not sure if Mercury or Yamaha have their own brand?? They should?

​The grease is real important when the bearings are reassembled they won't stick unless you use grease to hold them in place.

​Too bad on the no striper :(
​They are one of my favorite eating fish.
​When I lived in Md. I lived on board for 15 years.
I used to throw scraps of food over to the ducks and gulls.
​Then one day I noticed as the food settled the stripers were cruising and catching the bit of food the birds missed.
So I started catching them on bits of bread.

The last month or so the trout in the river are cooperating real nice.
​From the spot I fish: Ribbon Fish, Trout, Flounder, Jacks, Snook, Bluefish and 1 Pelican.
 

brianq

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You lived on a boat for 15 years?! That is pretty awesome. I agree striper is delicious nothing better then eating something you caught. I have never had trout.

The fuel pump was working I just assumed I should rebuild it since I am redoing everything else. Seems pretty simple with the correct kit. Machine shop is killing me called to confirm the head was ready and he must have left early today. There goes a potential weekend of progress.
 

jerryjerry05

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Maybe he's there today??
​Usually the pumps is god unless the diaphragm has a hole or stretched way out.
​Even stretched it should work, just not as effective.
 

brianq

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Machinist honed the cylinders today and found a gouge in one. He instructed me to return the 3.375" pistons and order the 3.405" pistons and bring him them and he will bore the cylinders 0.030" to the size of the pistons. Now we wait!
 

brianq

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Finally got the power head back from the machine shop! Hes going on vacation starting today so I am very glad to have picked it up this afternoon. A few pictures of the bored cylinders are below, he told me the 0.030 we bored was just enough to remove any marks from the damage. I paid $150 for the work seems like a pretty good deal. Today re-assembled the fuel pump and sanded down the damage on the taper on the crank shaft using 60grit sand paper. It is much smoother then it was but not perfect. Do i keep sanding so there is no visible marks on the taper at all? Sanded for a long time to get it to where it is. Tomorrow I plan to continue refreshing the crank shaft, clean and reset the bearings and install the new pistons.

There is a gap between part of the fuel pump and the cover which mounts on the block. I have attached a picture, is it supposed to be like that? My pictures arent good enough to confirm .
 

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jerryjerry05

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The pump looks right.
The black stuff on top of the head.is gasket residue. It's gotta be shiny.
​The taper is good enough. Just make sure you torque it right.
​85# on the flywheel nut.
The head needs to be at 225in pounds.
​Or 20# I use a 3 step torque procedure.
​Start at 15# then 18# then 20#

​You can use the old bolts as there is almost no stretch at 20#

I use a wire wheel on a small die grinder.
​You can take off too much so don't dig too deep.

When re assembling the crank.
There are locating pins on the block.
They stick up about 1/8"
​The bearings have a hole that sets on the pin.
​You GOTTTTA get them right.
Or the crank won't spin free.

 

brianq

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Today I cleaned up the crank shaft and reassembled with the bearings all cleaned. I also cleaned up the crank case cover. I attempted to separate the pistons from the control arm on a vice using two sockets and they wouldnt budge? I even had a friend helping me turn the vice to no avail. Any suggestions?
 

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