Mercruiser 470 compression test.

Kauaiboy206

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Its a 1980 mercruiser 470. I've got the entire engine & outdrive serviced, oil & a/f changed, plugs changed, n?w solenoid & ignitor, the boat doesn't wanna start. Confirmed I've got spark on all four cylinder, battery charged & gas in tank. So here lies my next dilemma; like I mentioned on my other post, 1-4 cylinder got a pressure reading of 120-135 although I think #3 has 118, did it twice and we're consistent on both reading. It cranks well but it just don't wanna turn over. Sometimes the carb makes this air purge noise, but nothing. Sometimes it almost turn over then not. I may have poured too much oil, a little over the full line, so I might end up realeasing some tommorow.
When I changed the oil, it was a little dark but no signs of water nor it was milky. Not sure how to check if gas is getting fed, but it's wet when I look down the carb. What should be the ideal reading for these engines also? Might end up performing a leak down test this weekend but I still need to learn how to perform such task still.
 

Maclin

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Was it a runner before you did all that, and just did it for normal maintenance? Or did you do all that because of some problems?

When you say new solenoid and ignitor, what is the "ignitor"? Are these both Starter components? Or did you fix something in the distributor.

You said changed plugs, what did you do with distributor components? Did you check dwell and timing? (Dwell if points type still).

Do you pump the throttle 2-3 times before attempting to start?

You can check for gas at the carb with a helper, look down the throat of the carb and open throttle more than half way closing quickly and watch for gas squirting out the accelerator pump nozzles out into the bore, should be a good solid stream and can even hear if from the helm sometimes.

If no gas in the carb it should still try to start when you pour a vary small amount into the carb bores and crank. If gas is in the carb and still the engine won't catch then I would suspect ignition timing.

Those comp numbers sound a little low, but out of the water it should still start. In the water with more backpressure is when bad compression will show up.
 

Kauaiboy206

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Was it a runner before you did all that, and just did it for normal maintenance? Or did you do all that because of some problems?

When you say new solenoid and ignitor, what is the "ignitor"? Are these both Starter components? Or did you fix something in the distributor.

You said changed plugs, what did you do with distributor components? Did you check dwell and timing? (Dwell if points type still).

Do you pump the throttle 2-3 times before attempting to start?

You can check for gas at the carb with a helper, look down the throat of the carb and open throttle more than half way closing quickly and watch for gas squirting out the accelerator pump nozzles out into the bore, should be a good solid stream and can even hear if from the helm sometimes.

If no gas in the carb it should still try to start when you pour a vary small amount into the carb bores and crank. If gas is in the carb and still the engine won't catch then I would suspect ignition timing.

Those comp numbers sound a little low, but out of the water it should still start. In the water with more backpressure is when bad compression will show up.

Was a runner prior to getting the boat; did a test run on a lake twice the same day when it was picked up. Once before the exchange & another in the afternoon which was runner about 1hr or so in a the lake. Changed the solenoid since it was showing too much rust, the ignitor didn't check out well when I did the ohm test "reading was inconsistent and was numbers was jumping all over the place" new ignitor wires but didn't check the distributor yet, I was told it was upgraded with a petronix so I don't have to worry about setting points.
 

Alumarine

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When you say ignitor do you mean coil?
Are you sure the plug wires are on correctly?
Firing order is 1-3-4-2 I believe.
 

Maclin

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You have spark at the spark plugs, is it bright blue or more yellow. And yes, with pertronix no need to check dwell if initially installed correctly and timing set.
If distributor was not disturbed then no need to check.

Are you sure the sparkplug wires are in the right spot on the distributor. Would be good to verify that even if you are sure, good doublecheck.. You can check easily by getting the number one cylinder to top dead center on compression stroke, and look under the distributor cap to see what terminal the rotor is pointing at. Be sure it is TDC on the compression stroke. Whatever the rotor is pointing closest at will be the #1 cylinder. Sometimes during a previous distributor R&R it may not have been clocked correctly and causes problems for the next owner when they change wires.
 
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Kauaiboy206

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When you say ignitor do you mean coil?
Are you sure the plug wires are on correctly?
Firing order is 1-3-4-2 I believe.

The one bottle looking thing that the one main wire is connected to the distributor. When I replaced the spark plugs, I marked the wires with numbers just incase but I replaced them one by one so I don't think I would've have plug them any different prior to the way it was originally plug when running.
 

stonyloam

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Are you advancing the throttle when you start? Push in the throttle only button and give it about 1/3 throttle?
 

Kauaiboy206

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You have spark at the spark plugs, is it bright blue or more yellow. And yes, with pertronix no need to check dwell if initially installed correctly and timing set.
If distributor was not disturbed then no need to check.

Are you sure the sparkplug wires are in the right spot on the distributor. Would be good to verify that even if you are sure, good doublecheck.. You can check easily by getting the number one cylinder to top dead center on compression stroke, and look under the distributor cap to see what terminal the rotor is pointing at. Be sure it is TDC on the compression stroke. Whatever the rotor is pointing closest at will be the #1 cylinder. Sometimes during a previous distributor R&R it may not have been clocked correctly and causes problems for the next owner when they change wires.

I used a tester to determine for spark, the on the lights up when it is cranked. I'd have to look up the process on checking the correct plugs, never did one before. I did remove the plugs one by one to check if any has corrosion but placed it right back in the same slot on the distributor.
 

Kauaiboy206

Petty Officer 2nd Class
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Messages
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Was it a runner before you did all that, and just did it for normal maintenance? Or did you do all that because of some problems?

When you say new solenoid and ignitor, what is the "ignitor"? Are these both Starter components? Or did you fix something in the distributor.

You said changed plugs, what did you do with distributor components? Did you check dwell and timing? (Dwell if points type still).

Do you pump the throttle 2-3 times before attempting to start?

You can check for gas at the carb with a helper, look down the throat of the carb and open throttle more than half way closing quickly and watch for gas squirting out the accelerator pump nozzles out into the bore, should be a good solid stream and can even hear if from the helm sometimes.

If no gas in the carb it should still try to start when you pour a vary small amount into the carb bores and crank. If gas is in the carb and still the engine won't catch then I would suspect ignition timing.

Those comp numbers sound a little low, but out of the water it should still start. In the water with more backpressure is when bad compression will show up.

Also i never pump the throttle more than once, only one full pump then return it from 1/4 away from the center. Am I soppouse to be letting in that much gas for a cold start? I was afraid I'd flood the carburetor or something. By the way interior of the carb looks clean, the walls are wet and doesn't have any build up or dried up white marks etc.
 

Maclin

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What wire are you using to run the spark tester? On one of the sparkplug cables, or the one at the center if the coil (igniter)? If just at the coil, then can you use it to check at the end of each sparkplug cable one at a time? This will determine if the spark is getting thru the rotor and on out to the sparkplug.

Did you take the distributor cap off at anytime during this process?
 

Kauaiboy206

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What wire are you using to run the spark tester? On one of the sparkplug cables, or the one at the center if the coil (igniter)? If just at the coil, then can you use it to check at the end of each sparkplug cable one at a time? This will determine if the spark is getting thru the rotor and on out to the sparkplug.

Did you take the distributor cap off at anytime during this process?

Never messed with the distributor cap at all, although I should just to check for any corrosion. The tester I got requires me to use as a link between sparkplugs & the wire so I checked every single one of them.
 

Kauaiboy206

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On a cold start I would do 2-3 pumps to past halfway open.

Confirmed I've got gas squirting as I move the throttle, pumped 3 times almost turned over then puffed a white smoke from the carb. Tried just cranking with no more pump but throttle moved forward & still no sucess
 

Maclin

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Make sure the coil is wired right, purple wire on the plus and the wire that comes from the pertronix unit on the minus .

I do keep coming back to something out of time where spark is not happening at the cylinders at the right time. Are you sure the sparkplug wires are on the cap in the right order, and need to be real sure that the #1 terminal is really number one cylinder when at tdc. If you are not sure that is correct then here is simple way to get #1 cylinder close to TDC (top dead center) on compression stroke.

Take #1 spark plug out, be sure it is the number one cylinder. I do not know on this engine if it is marked anywhere on the had or manifold or block. You may need to look it up if you are not sure.

Unhook the wire coming from the center of the coil to the center of the distributor at the coil.

Crank the engine and listen for the big puff of air out of the open spark plug hole. Quit cranking right when the puff is biggest.

May need to crank it a few times to get close as possible to apex of the puff.

Then unfasten and lift the distributor cap and see which terminal the rotor is pointing at. That will be number one on the cap no matter what any stamped numbers show.
 

Kauaiboy206

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Update- got the motor started up, I drained oil off since there was way too much of it & it fired up. I was able to get thermometer reading on various places, manifolds heat exchangers etc all the rubber hoses. The highest reading I got was at 120-155 degrees. But when I directly point between the head and the exhaust manifold, the reading goes higher around 180-190 also went up to 215, is this normal? The exhaust manifold or where the anti-freeze goes to is @155-160 but once I move it over to the link between head and the manifold, it gets higher in the 205-220.
 
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Kauaiboy206

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Those are the areas whete IR Thermometer reading is above 200+, everywhere else is normal below 160.
 

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2fishy4u

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I get the same hot spots on my 470's. Its good temp in all the right spots, but right at the head to exhaust connection I get a little high like you on number 3 200-210. As long as its running at 165 or below on your gauge (and the gauge is correct) you should be fine.
 

Kauaiboy206

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I get the same hot spots on my 470's. Its good temp in all the right spots, but right at the head to exhaust connection I get a little high like you on number 3 200-210. As long as its running at 165 or below on your gauge (and the gauge is correct) you should be fine.

Good to know, I did take the boat out this past Sunday for a test drive, she did pretty good but when I started to go full throttle @4500 rpm & above, she statted to stress out a little. Reading creeped up above 190' so I throttled it back at 3500/3800 and was all good' average speed was around 27-30 with 3 adults & 3 kids. Maybe I didn't have the boat properly trimmed so it might have been burdened on the weight. Still new to boating and this is my 3x taking her out.
 
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