Mercrcruiser 1986 3.7L 170 possible seized?

[dancewithme951]

Scoured the forum and did not find a solution to my problem so here goes. I just purchased a 1986 Mercruiser 3.7L 170 HP as part of a restoration project. The previous gave up on the project and I thought what the heck, why not?! The engine/outdrive were removed from the boat so I set out to test the engine (the previous owner claimed it ran before disassembly). Connected wiring harness, gauges, fresh battery and tried a quick dry crank via the ignition switch before further plumbing and the starter/solenoid just clicked rapidly...no turning of the engine. For those familiar with this engine I tried turning the flywheel looking disc in the front of the engine (I know what it is it's the alternator/closed system water pump but it would not budge. There were 3 threaded bolt holes on this "flywheel) so I inserted 3 suitably sized boltd firmly in the holes and tried turning with a crowbar but still no movement (tried clockwise and vice versa). Next I removed all 4 spark plugs to eliminate compressive resistance but still no luck. Pulled the starter with attached solenoid (there's also a separate "slave" solenoid which did click with each attempt) and bench tested it and it worked just as it should with the bendix thrusting the engagement gear vigorously.

It would seem the engine is seized. I've squirted a genorous amount of WD40 into each cylinder and will let it sit overnight
and try again tomorrow. Any thoughts as to further maneuvers that could be tried short of doing an engine disassembly?

 

[Bt Doctur]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

You could get an old input shaft from a drive and weld it to a "T" bar. inserted into the coupler makes a nice too for turning the crankshaftl .

 

[searay3]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

If the drive is off and the spark plugs are out and you can't turn it over by hand with a crowbar, nothing left but disassembly.

 

[dancewithme951]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

Just for my own education, what exactly is the clicking I hear when I try the starter? Is that one of the solenoids engaging then disengaging repeatedly? Can anyone tell me what the slave solenoid is for? I've never seen one of those before. Why is it needed?

 

[Bt Doctur]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

With boats ,the starter is too far from the ign switch .So a small gauge wire is used for the start circuit. So from the key, to the slave solenoid, then to the main solenoid. If you look at a wiring diagram you will see the heavier wires are used on the enginbe ,not under the dash. There are 2 large wires in the harness, a red or red/purple and a black., This supplies power to the dash area.

 

[dancewithme951]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

Gotcha! I now understand the need for the slave solenoid.

 

[Pete104]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

Forget the WD-40. Mix up some ATF & diesel fuel (cup of each) and put some the cylinders. Couple ounces each maybe a little more and just let it sit. Add some in a few days.

Stop prying on the front of the engine, turn it from behind as pointed out above.

 

[dancewithme951]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

UPDATE: engine sat with penetrating oil in cylinders and this orning it finally budged. After turning it several ties anually, it slowly letting loose, gave at a few cranks with the starter. Then put in about a quarter cup of 10W-40 through each spark plug opening...followed by more manual cranking, then starter cranking. It doesn't turn all that well but at least it's free. Not sure what the next approach should be. Any ideas?

 

[harleyman1975]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

Man if you are going to all the trouble of restoring a boat why would you even consider puting in an engine that has a bad rep on a good day and then, not to mention, one that is in questionable condition? If you really want to reuse this engine you should disassemble it and completely rebuild it and update it...I would part that thing out and repower boat with a 3.0 or a 4.3 with all hardware including outdrive from a doner boat. there are lots of them out there. That 470 is the "YUGO" of marine engines. Sorry if I am coming on a little strong. I know we are supposed to be here to give instruction and advise. Just hate to see a guy pounding himself with a hammer because it feels so good when he stops.

 

[dancewithme951]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

I hear ya harleyman. But I'm kinda fond of orphans/stepchildren. I also have a Force 125HP that I'm giving some love too and she's just as ridiculed as the Mercruser 470. But ultimately it will also be economics. If the reason for seizing is something as simple as rust, and I ger her running, I'm looking at a marine alternator upgrade (do it yourself for about $100) to replace the existing ststor/water-cooled voltage regulator and a very cool design I found for running in series dual 3" heat exchangers. These two inexpensive modifications will eliminate the 470s major achilles heels.

 

[Walt T]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

That engine is junk. Cut your losses.

 

[Maclin]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

The magnets on the inside of that part you described as "flywheel looking disc" can come loose and double over and then can generate enough friction to stop the engine from turning sometimes. The alternator mod is a good one for that engine, but be sure to remove all those magnets as part of the upgrade..

 

[Maclin]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

Then there is what Walt said...

 

[Maclin]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

If you stick with it I would try to find or refit a 4" exchanger to fit in the same space. With your rescue-a-stray approach youi may end up spending a dollar to save a negative 50 bucks, with no love in return, just sayin'...

 

[dancewithme951]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

Thanks Maclin for your insights. Gotcha on the magnets...read about those elsewhere. And a 4" heat exchanger is approx. $400 so that's not in my budget. Used ones on eBay are about $400 and, if you can believe it, 3" ones in good condition for $275. For such a dog of an engine you'd think used parts would be CHEAP...people parting out and wanting to get rid of them.

I'll see first if I can get the engine free cranking with plugs in. Then I'll check compression. Then see if she'll start...hah! I likely see a teardown in my near future. Then it'll be sh** or get off the pot time! Thanks again for everyone's feedback.

 

[wrestling coach]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

OP private message sent

 

[Walt T]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

Boat ownership does not lend itself well to those who are financially challenged

 

[dancewithme951]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

On April 1 I gave an update - what I viewed as a positive development (motor unseized, it doesn't turn all that well but at least it's free). Not sure what the next approach should be..any ideas? I'm hearing mainly negative comments and believe me I've read all about this engine's faults. But surely there are owners of this engine out there who have constructive/helpful advice? I've never completely rebuilt an engine before and hope this one will not require that.

This engine was in a 1986 Four Winns 170 Horizon - a very nice boat. It has a great hull - looks nearly new - and the previous owner had gutted the interior and started the restoration of the floor. He had been told the engine ran so I went on that (with healthy skepticism of course) but for a mere $500 I bougt a dismantled but complete engine/outdrive, complete but dismantled hull, 70 yards of fiberglass with equivalent amounts of resin, mixing buckets, etc., a 2000 lb hydraulic hoist, a marine upholstery sewing machine with extra needles, attachments, etc., and a great trailer with new tires. So, the hull restoration will be nearly all labor on my part - I'm retired so I have the time. So I'm way ahead money-wise but know that, even fully restored with running engine, this boat will still only be worth maybe $5000, I don't want to sink several thousand dollars on an engine - this one or a replacement. I would LIKE to get this engine running, and even add the improvements I mentioned (upgraded alternator, enhanced heat exchanger) and stay under $1000.

So if there are forum members supportive of my goals I would like to hear from you. I'll pose again the question. I have the engine turning over (with plugs removed) with fully charged battery but it's still very sluggish in its rotation, even after penetrating fluid - which broke it loose - then 10W-40 in cylinders, more penetrating fluid (Pete 104 I saw your advice on the diesel/ATF but since the enging freed up on just penetrating fluid I held off on that..still useful at this juncture?).

Any suggestions that might further loosen internals to get it free cranking so I can then fuel it, attach water, and see if she'll run?

 

[Maclin]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

Recently this hate-love topic with the 170/470/3.7lx here did bring out some positive players. With all the upgrades addressed on a solid engine (good compression, etc.) they are a powerhouse, maybe kind of loud and vibratey at idle.

You can turn up some positive posts about this engine here with a good search, and maybe the lovers will chime in here soon.

If a person is up for all the challenges this engine produces in ADDTION to just owning a boat with a supported engine, then there is a certain pride and sense of accomplishment to be garnered. It just seems the oppposite occurs more often

There are worse combos to try to keep alive, though not many. L-Drive comes to mind :wacko:

 

[Bondo]

Re: Mercrcruiser 1986 3.7L 170 possible seized?

On April 1 I gave an update - what I viewed as a positive development (motor unseized, it doesn't turn all that well but at least it's free). Not sure what the next approach should be..any ideas?

Any suggestions that might further loosen internals to get it free cranking so I can then fuel it, attach water, and see if she'll run?

Ayuh,... Have ya got the Drive off, so yer turnin' Only the motor,..??

Any motor that is so seized that it won't turn over,...
Will Never be a Reliable motor, unless it's torn down, 'n fully Rebuilt,....