Logo
FULL SITE MENU

Water temp gauge/carb./distrubutor

M

mashed_finger

Member
Hi all..., I'm back, it's been awhile, and things have changed some on the site, still though, it's the best fix it forum around! First off, I have a 1992 OMC cobra with the 5.0 ford V8. I have been throwing parts at this sucker like crazy. Been having what I thought was an overheating problem, so I tossed parts at that like a drunken sailor. So I took it out today and it appeared to heat up to about 200-210 degrees, so I came home and had a brain fart of an idea. I have a fancy little hand held multi meter that just happens to have a temp setting with a nice little skinny wire probe. So I yanked off the big "U" tube and stuck the probe down the inside and put it back on the engine. I started her up and got up to the same high temp with muffs on, as it did at the lake. Long story short, the hand held multi meter read only 153 degrees, while the boat temp gauge read between 200-210. It would appear that I have a faulty gauge.
Question I have is, the gauge has an o/d of approx. 2 3/8" dia., Which are the good and very accurate brands to buy, and do they come with their own senders? THis problem has been worrying me sick, since I just put in a new Mallory magnetic pickup distributor. How hot is safe for them to get, I measured the outer case at around 138 degrees..., just wondering.

I also got the old Holly single pumper 600 cfm rebuilt (marine), I am kind of sorry I did, as it cost me a months liquor budget. I am having a hard time getting it to idle, just when I think I have it adjusted, when I come off plane, the idle is too high. When I shut off the key and restart, it either idles normal or too low..., and yes, I just put in a new CDI ESA, which seems to be working normally. This is making me crazy, I was told that fixing a Holly is a waste of money, and that I should just go and buy an Edelbrock..., I hate it when I am wrong...., good thing I am not a gambler.

As usual any help from you experts would be most appreciated. I won't be boating much the rest of this month, the tub goes in for an all new interior, with new rear bench and captains chairs...Ka ching. Thanks for the help in advance.
Rick
 
G'day Rick,

I just experienced exactly the same overheating problem as you.

I have a 1973 Chris Craft Gull Wing 16 footer with a 225 Buick V6, which I totally rebuilt the whole kit and caboodle. And Stewart Warner Gauges.

Took her for her maiden run since she saw the water in 2001, and everything was running well, till I noticed that the Temperature Gauge was off the scale at 240 Degrees. Boy, did I shut her off fast. Whilst floating on a 2 Knot Current, away from my destination, and with too far to paddle, I let her cool down for a while, but couldn't see anything wrong, apart for a slight water leak of hot water from a bolt head.

Anyway, Decided to motor back slowly, and I kept the eye on the gauge, and much to my surprise, the gauge fell to 200, then back to 240, and fluictuated up and down till we got back to the ramp.

Well, to cut a long story short, hang on, I have just typed a long story...........

But, I purchased a Laser Thermometer, and testing proved that the Gauge was reading 35 Degrees high.

Testing the Sender Unit with a Multimeter, I found that with the Ignition on, but the engine not running, the Voltage at the Sender was showing 9 Volts and with the engine idling, 10.5 Volts. (Engine Cold) This got be thinking, and realising that the Alternator was pumping extra voltage to the Sender, as though there was a Voltage Regulator missing. Gauges usually have a standard Voltage, around 8 or so Volts, so that the Gauges are reading correctly, no matter how high or low the Battery Voltage is.

When the engine was hot, after normal running temperature, with the engine off, but the ignition on, the Laser Temp showed 195, the Gauge 230, and the Sender Voltage was 5.1 Volts.

Your Fast Idle problem sounds like a Throttle Lever not fully closing, and/or a Vacuum Leak. But then, it idles too slowly, but don't forget, you are starting it with the shift in Neutral, so there could be some sticking within the Morse Cable.

Bruce.
 
Rick, tossing parts at a problem, and enough parts, will eventually fix the problem. Not the best approach, IMO.

Maybe this will help:

First off, realize that the thermostat will be holding coolant (aka sea water) back in the engine block/heads until it senses temperature! Only then does it open to allow coolant to be released. It's just the nature of the way the stat works.


Secondly, most of your sea water (if all is working correctly), is by-passing the engine, and is being sent on to and through the exhaust system, and out!
Think of it as the engine (via Circ Pump, T stat housing and T stat) using coolant on an "As Needed" or "On Demand" basis!
Again, most is by-passing and going on to the exhaust system and out!
Doesn't matter which make.........any Raw Water cooled Merc, Volvo Penta or OMC!
Point being, if you want a more realistic temp reading, it must be taken just prior to the coolant leaving the engine...... and if you'll notice, this is where the temp sender port is usually located.


One member recently posted that a previous impeller had lost several of its blades.
Apparently these blades had not been retrieved by the mechanic who did the new impeller replacement. :rolleyes:
The pieces ended up restricting flow at the PS oil cooler where they were trapped. Once he cleared this, his over-heating issue went away.
Here is his thread!

Don't over-look the possibility of an automotive circ pump having been installed!
These have a steel or iron impeller that may be severely corroded by now!
The true raw water cooled Marine Engine Circ Pump will have the bronze impeller that resists corrosion.
If your impeller is all but gone, you will have over-heating!

All too often we look only at the sea water pump, and/or the T stat, when it may be a restriction elsewhere.
(I.E., Exhaust Man-to-Riser passages, flappers, porting within the T stat housing, and so on.)

Ignition advance can also contribute to over-heating, but usually results in engine damage if left un-checked for long.
When you set BASE advance, also check to see where your TA (total advance) is. This too is often over-looked!


I'm not suggesting that these are your problem, just tossing this out there so you can arm yourself with it!
 
Last edited:
Without a doubt Faria gauges. Have had nothing but trouble with Teleflex, and I hate the mounting hardware.
The senders come in either single or dual.

Rebuilt carbs are a waste of money. Buy new, it's not that much more and you get all new parts, not a mashup.
 
Thanks to all who replied I appreciate the advice. Bruce the Aussie, thanks for the heads up on the gauge/sender/voltage suggestion..., that one got by me mate. I have a rebuilt Motorola Alternator and it holds steady at between 13.8 to 14.4 volts depending on what accy. I have on at the time. My temp gauge never wavers, it goes from 0 to 205 degrees and sticks there, but I will test the voltage at the sender, it's brand new, but does the same thing the old one did, only it works, where the other one would when it felt like it. I must check out the Stewart Warner gauges, along with the Faria.

As for the carb., some one told me that Holly's are known for having erratic idle problems, with vacuum leaks being one of the main trouble areas. It has next to the electric choke, what looks like a brass compression fitting with the hole in the middle, I have no idea what it is for, but I do know that I can hear a little hissing coming from it, and when I put my finger over the hold, the hissing stops.

How many turns of the idle mixture screws should one make, the Seloc repair Manual says about one half of a turn, I have them at 1 and a half turns, and it still acts like it wants me to go more. When I do, the idle speed up, and the engine smooths out, and I can back off the idle speed adjustment, but then it is way off what the repair book says. If I put it where it would like to be, will I be wasting a lot of Gas; I don't really want to do that since the stuff ain't cheap. But, no worries, we'll get it figured out some how.

The temp gauge make in my boat has a little "A" at the bottom of each gauge, I think they are Accutrons..., but could be wrong. I don't have a terrible time tossing new parts on an engine that is 18 years old, especially since most all of them were the originals. You know, Jesus used to boat some, and if something happened he could get out and walk on the water...., I haven't been able to do that yet. So I figure any new part I put on, is one less part that fails when I am out in the middle of one of our really big lakes around these parts.

Besides, most of the mechanics around here are new part's tossers, and as some have told me, "well, lets see how that works, if that ain't it, well try sumpin else". My shade tree mechanics license may be a bit out of date, but even I can do that, and for a whole lot less. Besides, I read all of the overheating advice I could read on this site, and replaced every thing every one suggested, which I think was a pretty good idea. I stuck the hand held multi meter thermostat probe at the top of the big "U" tube, and ran it up in to where it was within 2 or 3 inches from the sender, I thought the reading I got was pretty accurate..., I could be wrong. I then placed the probe next to hot engine parts while it was still running, and it would measure about 15 degrees less.

I have a new out-drive water pump, that will shoot a nice column of water from the main intake hose, and there is a noted difference in temp and the top of the thermostat housing as compared to the bottom, and I also back flushed all the hoses with my garden hose, and the exhaust manifolds stay quite cool while the engine is running. The exhaust man flappers flap like they are supposed to, and I have a new bronze fitted engine circulation pump on the engine. The old one was an automotive pump, the new one works much better, because my hoses are all much tighter than they while the engine runs than they were with the old pump.

The new distributor is a Mallory magnetic pickup, with a 24 degree advance curve, is that normal, or to much..., I am not sure. So as far as I can tell, it must be the gauge, but I am still open to suggestions.

As for having the old Holly 600 rebuilt, I am going to have my wife slap we up along the back of my head, after she kicks my butt..., I hate fussing with that thing. Anyway, thanks to all who replied I do appreciate it!

Rick
 
Back
Top