"true ignition"? and another exciting story

dschock · Outlaw Joined: 07 Apr 2004 Posts: 135 City: Bellevue

The isolator and second battery all seemed like an easy solution for listening to tunes while floating for hours in the sun, but all of a sudden the wiring seems way harder than expected.

What would you recommend I use as the "true ignition" source for my Stinger SR200 isolator to activate it.

Also, do I run the ground from the isolator to both batteries? or one? which one?

all seemingly simple questions, if someone out there could please give an answer it would be greatly appreciated

oh and check this out... first day out on the lake in our new to us 2000 Tige 21V, cruising around for half hour no problem, then idle to go under a bridge, pop out the other side, and BAM, heat jumps like a million degrees. Great day for the impeller to go out. Why do they make those out of plastic in MerCruisers anyways. Long story short, dad's not gonna spend money to get home, lets it cool and gets it up to high rpm's, where it can still stay relatively cool, but after a little while it heats up again and then... SEIZES... yup, looks like a few new piston heads for us... anyways, just thought I'd vent. If anyone wants to share a similar story, it would make me feel very comforted. I literally just finished installing the new stereo and have a new Titan tower on the way with Bullet speakers, and all get to sit around for a few extra weeks... i'm really excited Crying or Very sad

Nor*Cal · Ladies Man Joined: 12 Jan 2003 Posts: 9479 City: Sac

bruttenberg · Posted: May 19, 2004 4:03 am Post subject:

that sucks man sorry to hear it.

I have the SR200 connecting 2 Optimas in my boat. I ran the true ignition wire off of the back of the fuel guage. There are 3 posts on the back of the guage - find which one is hot with a 12v light tester. Make sure you have a good ground though or you'll be searching for the hot wire for some time.

That's what I did - I'm not positive that this is the correct way but it has been working so far. You will hear a noticeable click from the relay when it does receive juice. Hope that helps. Also would like to hear from others whether the fuel guage is an appropriate true ignition source or not.

tommyadrian5 · Addict Joined: 16 Sep 2003 Posts: 907

Want2ride · Outlaw Joined: 13 Jan 2003 Posts: 182 City: Layton, Utah

My thoughts exactly Confused

BIZ · Outlaw Joined: 19 Jan 2004 Posts: 184 City: Dallas

More than likely the high rpms allowed more water to be pumped through the engine than at low rpm's with a few missing vanes on the impeller, until the impeller completely failed.

hindsight is 20/20, the lesson learned here is you should always carry around an extra impeller!!!

tommyadrian5 · Addict Joined: 16 Sep 2003 Posts: 907

BIZ, engines don't need anything above a drip of cooling water to remain cool at idle, which is why when cc's overheat it limits the rpm instead of shutting the engine down completely

DiyGuy · Soul Rider Joined: 26 Dec 2003 Posts: 460

I've also heard that it is possible to run at a high rpm with bad impeller, enough so to get back to shore with it.

I've never tested it, but can understand how that might work. The entire thing doesn't totally disentegrate, but high RPM might allow it to spin fast enough to keep water to to circulation pump.

Easy insurance - keep a spare - at max....a 15 minute change out.

Magic · Outlaw Joined: 27 Jan 2003 Posts: 240 City: Seattle

Running the motor with a failing impeller is also going to put little pieces of black rubber into other parts of the motor. You'll need to flush the entire cooling system, that means the tranny cooler too.

Once that impeller failed, I'm not sure how the boat would be pulling in lake water for cooling. Hence the overheated heads on the block.

A lot of people keep the old impeller as a back up in the boat when they change 'em. I'd rather bust a knukle or two and get a bit wet changing that on the lake than repairing the motor at the dealer...

gvb · Posted: May 19, 2004 11:22 am Post subject:

Shitty...

I've got a bag with everything I need to change the prop (underwater), impeller, spare plugs, drive belt, etc.. Things I still need to add are hose clamps and a length of hose to replace any peice of the hose that could crack while out.

Recommend that to pops. It sucks ruining an entire weekend after driving hours because of a $25 impeller that takes 15 minutes to change.

-gvb

dschock · Outlaw Joined: 07 Apr 2004 Posts: 135 City: Bellevue

[quote="tommyadrian5"]

DiyGuy · Soul Rider Joined: 26 Dec 2003 Posts: 460

So as to enlighten those on impellers and why you can run the motor at high RPM and still get water to the engine, enough to limp back to shore... the attached photos tell all.

As you can see, when an impeller 'blows', it does not totally disentegrate. Small shards come flying off, but there are still some vanes that are good enough to move water. Not at low RPM, because it simply isn't spinning fast enough, but when spinning fast it will pump water and watch your temp gage come down - still may be high, and obviously if over 220 or so, SHUT IT OFF.

Second, is to dispell a myth mentioned earlier. The first trap in line to catch all the broken pieces is the transmission cooler. In the other photo, you can see how small bits of rubber have been trapped by a grate or screen - actually it looks more like small honeycomb that traps anything before it gets to the engine recirculating pump, or as was hinted, into the engine. I will NOT get into your engines cooling ports because the folks that built the tranny cooler were very smart people. They actually figured this would be a good safeguard to protect the engines small cooling lines and channels inside. Brilliant thinking!

So, again, the best insurance is to carry a spare with you - a couple of screwdrivers, some long nose vice grips (to clamp onto what remaining rubber there is) and deliberately work the old one out. Slime up the new one with anything you have on board (sun-tan lotion, boot slime, soap - anything slippery), and put it back on, replace cover.

But, you see that is only half of the procedure. You need to disconnect the water line from the output side of the impeller pump to the transmission cooler and shake out all the small bits of rubber that are gunked up. Also a screwdriver or something to poke up the bottom of the transmission cooler itself to get all those tiny rubber pieces, THEN you put it back together and on your way until the next time.

It's all very elementary stuff - no magic - just good common sense.

lcap · Ladies Man Joined: 13 Nov 2003 Posts: 10973 City: Homeless

DiyGuy

Hate to be the one that disagree with you but sometimes an impeller does "blow" and it does not move anything!

Sucked up a plastic baggie next to a dock and all heck broke loose. Within a minutes of startup alarms started going off, lights were flashing, engine shut down and smoke was everywhere.

It got so hot it melted the fiberglass exhaust. No engine damage but over $600 for a new exhaust.

I always carry an extra impeller and once I notice the engine starts to go over its normal operating temp, I replace it.

MrBlean · Posted: May 20, 2004 1:46 am Post subject: Fallacy

I have to disagree with some of DiyGuy's comments too. On my Indmar equipped MC the tranny cooler is in the input line to the impeller. The strainer takes out weed etc but is in front of the impeller so how could it screen out parts of a disintegrating impeller?

Answer is, it doesn't, that's why I have found bits of impeller in my exhaust from a failure under a previous owner.

Also, it's not the speed of an impeller that's most important. It's the fact that the blades seal to the side of the pump body. Short blades that do not reach the edge can spin as fast as they like but will not pump much water. If you look at the way the impeller works, the volume trapped between the blades changes depending on the position within the pump.

Water gets progressively "squashed" (water is almost incompressible so it's under pressure rather than reduced in volume) and carried around to the outlet side of the pump where it squirts out.

If the blades do not reach the side of the pump body, no "squashing" takes place and water just moves around inside the pump as the impeller circulates within it.

Usually the blades don't all fail at once so it's simply a cse of inefficiency to start with but once it starts to fail it progesses rapidly so BIZ's explanation is probably the most accurate.

I am not at all familar with Mercruisers but the impellers on Indmar conversions and on the Mercury outboard I used to own are made of a rubber-type plastic i.e. they are fairly flexible and do perish (crack) as opposed to harder plastics that tend to wear rather than crack. I cannot imagine that those on Mercruisers are any different but I could be wrong.

Anyway, the moral of this story is that any sign of a failing impeller is a good enough reason to stop the motor 'cos the cost of fixing the end result (warped heads, seized pistons) is so great that I don't understand why anyone would risk continuing.

Lesson learned the hard (and expensive) way!

bruttenberg · Posted: May 20, 2004 3:14 am Post subject:

what about the true ignition? OK to run off of fuel guage?

dschock · Outlaw Joined: 07 Apr 2004 Posts: 135 City: Bellevue

Good news from the dealer: Looks like we got away with only a couple warped heads and apparently no damage to the cylinders. Should be back out on the water in a week. Phew.

Back to the "true ignition" Q tho... is the fuel gauge okay to run it off of? Also, anyone know where I can find a wire in back?

Thanks