Idle RPM

millz90

millz90

New Member
Oct 1, 2009
175
North Carolina
Boat Info
1995 Sea Ray 175
Engines
3.0 Mercruiser Alpha I
Just wondering if anyone knew what the RPM's should be on a 1995 175 Series Sea Ray at idle?

I have mine set to 2 thousand RPM's right now but it seems a little high, and loud but if i adjust it down to 1 RLM it sounds to low like its going to puff out and stall?

Any ideas?
Thanks!
 
A "little" high?!?! It should be somewhere around 650 - 700!!!!!

Do yourself a favor and invest in a service manual. It's money well spent.
 
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Well if i turn it down and it sounds like its going to stall what should i check to see what the problem is? Any ideas?
 
Check plugs, wires, distributor cap, coil, fuel, carb, timing, compression, etc. Agree with Dennis - should be will under 1000 RPM - and more in the 600-800 range. How does it run otherwise? If it only runs bad at idle, it will usually be carb or vacuum leaks (too lean or too rich).

The faster RPM idle will be hard on the outdrive slamming in and out of gear. And I can't even imagine how fast your slowest speed in gear might be...
 
millz90 said:
Well if i turn it down and it sounds like its going to stall what should i check to see what the problem is? Any ideas?
Click to expand...

Wy don't you start with basic items, when was the last tune up done?
 
Alex F said:
Wy don't you start with basic items, when was the last tune up done?
Click to expand...

I just bought the boat so im not sure. The engine looks pretty clean and i paid to have it winterized last winter...draing the gear lube and replace.

What should be done for an actual "Tune Up"

What does that consit of?
 
The basic tune up list includes the following:
-plugs
-wires
-rotor
-cap
-fuel filter(s)

Mine 1997 175BR had carb., so I'm guessing yours is the same, so cleaning the carb might be a good idea as well.

I'm assuming that the oil change was done as part of the winterizing.

I'm not sure your level of experience, but I get the feeling that you might be better off taking the boat to a professional mechanic and let him do what's necessary and provide his opinion.
 
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millz90 said:
what should i check to see what the problem is? Any ideas?
Click to expand...

All good ideas above - nothing that I can really add to that.

However, I agree with Alex. I'm all for DIY, but the more you mess with it - and please don't take offense to this, it's not meant to offend - without knowing what you're doing, the more likely you are to cause either permanent damage, or make it just that much harder (and $$$) for a pro to fix it.

Either way, I hope you get it figured out!
 
Well i have new plugs, new wires, new distruibutor cap...so i guess that would leave the rotor and fuel filter.

Do you have to adjust boats timing? If so could that be the issue?
 
Yes, boat motors need the timing set, just like car engines. But I doubt that is the issue. Timing off far enough to prevent idle below 2,000 RPM is going to have other major implications.

The rotor (while I would replace it), probably isn't the problem either. Nor is it likely the fuel filter (though I would definately replace that). Don't forget the water seperator if it has one.

I'm still thinking vacuum leak or carb issues.
 
I vote vacuum leak. Fire up the engine and listen to it. You are listening for a whistling or air sucking sound.

I think I read in another post about using a different test material that wasn't as flamable, but a few well placed shots of Gumout carb cleaner is great at finding vacuum leaks in a car. Don't hit the spark plugs, distributor, or coil. Just look for junctions where vacuum lines connect. When you spot one, give it a short hit with the Gumout. If you spray it on a leak, the engine will run differently, usually better. Too many Gumout fumes in a boat engine compartment is not good. Use your blowers, take small shots, and only try 3 or 4 places before shutting down the engine and letting the blowers clear the air before checking any more.
 
Yep. Use the little red tube on the nozzle. Try to only hit areas where vacuum lines connect. If you get it too close to the carburator or throttle body you will get a "false positive" and the engine will run a little different than it was before you sprayed.

The idea is that the vacuum leak will suck in some of the Gumout, which changes the mixture, which make the engine run different. "Different" usually means it will run a little better because with the vacuum leak, you have excess air in the mixture and the Gumout will act as extra fuel when it gets sucked in.

Just be EXTREMELY CAREFUL or you will fill your engine compartment with flamable fumes.
 
When spraying gumout on a running engine, please have a fire extinguisher in the other hand. This is going to end badly...
 
Naaa... I've seen this done literally hundreds of times by myself and others. I've seen guys do it with brake cleaner, starting fluid, and several other things in aerosol cans that I can't identify. I've never seen a single flash.

If he does it correctly, there won't be sufficient fuel for a sustained fire, or time to use a fire extinguisher. Besides... there wouldn't be a "containment vessel" for the explosive vapors, so it would only be a quick flash. He'd probably just lose his eyebrows. If he goes crazy and hoses down the engine with it so that it is wet (I did say short bursts...), then he might start a boat flambe. I'll nominate him for a Darwin Award right now if he uses that much.

I hope he understands that the idea is to use a shot just big enough to put some vaporized Gumout near the connection. Done correctly, the engine stays dry.
 
Spray works - and I've never had an issue doing it (though admittedly mostly on cars). You can also trace out the vacuum lines, and just disconnect and plug them all where they enter the carb base or manifold. But that won't find leaks such as those at the carb base gasket...or intake manifold gasket (though that is more rare).

Still, extinguisher is not a bad idea...
 
Remember that when setting the idle at 650-750 RPMs that Merc calls for that speed with the boat in the water and in forward gear. In other words, the engine should have a load on it. Be sure its tied up really good at the dock.

I have visions of a Sea Ray 175 in flames hurtling through a marina with lines dragging dock cleats.
 
the very best tool a man could have besides cash is a vacuum gauge, install into one of the intake runners and take a vacuum reading, to me it sounds carb related or vacuum related...they are about 19 bucks at napa, a properly running engine should see at least 16 inches of vacuum, if its down around 14, start troubleshooting
 
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