Another vibration topic - I need your input please.

[Redphone107]

First post, but I have been following the forum for a while and appreciate all the insight. Here is my problem. We just bought a 2004 Maxum 1800 with a Mercruiser 3.0 MCM Alpha One Gen 2. The previous owner hit a stump and had $7,500 worth of insurance work done on it. They replaced the transom mount, u-joints, impeller, bellows, and rebuilt the lower and upper units. The owner put a 4-blade prop on it.

When I crank it, I have a vibration at RPMs between 1500 and 3000. At higher rpms it goes away and doesn't vibrate much at idle. The vibration happens in gear and neutral. Also, it doesn't matter the level of the drive unit. It does it all the way up through driving position (say 3/4 down). It doesn't sound funny or anything, just a wicked vibration that you can see and feel. I read about maybe the harmonic balancer being out of whack. How can I tell if that is it? Also, are there any other thoughts on the issue?

 

[81 Checkmate]

It doesn't sound funny or anything, just a wicked vibration that you can see and feel.

Can you decribe the SEE the vibration? Prop, whole drive ect....
BTW - Welcome to ibotas.

 

[alldodge]

First post, but I have been following the forum for a while and appreciate all the insight. Here is my problem. We just bought a 2004 Maxum 1800 with a Mercruiser 3.0 MCM Alpha One Gen 2. The previous owner hit a stump and had $7,500 worth of insurance work done on it. They replaced the transom mount, u-joints, impeller, bellows, and rebuilt the lower and upper units. The owner put a 4-blade prop on it.

When I crank it, I have a vibration at RPMs between 1500 and 3000. At higher rpms it goes away and doesn't vibrate much at idle. The vibration happens in gear and neutral. Also, it doesn't matter the level of the drive unit. It does it all the way up through driving position (say 3/4 down). It doesn't sound funny or anything, just a wicked vibration that you can see and feel. I read about maybe the harmonic balancer being out of whack. How can I tell if that is it? Also, are there any other thoughts on the issue?

:welcome: to iboats

To find out if its the drive or the engine. Do this with the boat on the trailer. Remove the drive and remove the hose on the inside of the boat between your power steering cooler and the thermostat housing. Connect a garden hose to the hose going to the thermostat housing. Start the water running and then start the engine. Don't do this for a long time and try to keep rpms down as low as you can, but enough to see if the vibration is still there.

If vibration remains then its in the engine, if it goes away its in the drive or the prop.

You could also take your prop to a shop and ask them if it is balanced

 

[Redphone107]

Yes. It is the motor. It happens in neutral and in gear. On land and in the water. I changed the plugs, distributor cap, and rotor last week. We ran non-ethanol and it seemed to run really smooth once it warmed up. However, when I got home, I noticed that the power steering bracket (65606T) broke AGAIN. This is a $115 bracket and I have to pull the power steering pulley to change it. This is the second time it broke. I am having it welded tomorrow, but what gives? Could it be the 4-blade 18p prop on it? The whole drive was rebuilt and I don't think it has anything to do with the drive. Is it possible that the motor mount is too tight and doesn't give any and causes the vibration to be taken out on the attached parts? What else could it be? the only other thing I could think is that sometimes we get dieseling or run-on that shakes the motor. I am going to work on that next. Something with the carb wiring that causes it to send fuel after shutoff, I read somewhere. I will be checking the cabling., Any thoughts?

 

[Watermann]

Breaking alternator brackets is quite a bit of vibration beyond what I would expect unless one of the cylinders wasn't firing right. Some ideas... Compression test the motor looking for a bad cylinder with low compression. Try using a tester on the plug wires to see if one cylinder isn't firing right. It could be your rear motor mounts needing a bushing replacement kit but I think it would vibrate all the time. Your problem with run on will kill the motor. Since you ruled out bad gas with low octane, I would try running some MC power tune through the motor in case it's carbon build up on the pistons glowing red causing it the run on. Also be sure your idle is set right, too high will cause the motor to pull fuel through the main jets. If you can't get power tune you can try sea foam.

 

[flyman219]

That is very strange, so the starter bolts broke, were you replacing it or did it just pop off? The power steering bracket is at the other end of the motor and having three of them fail is very very odd. The vibrations you have noticed are they being generated from maybe a bent pulley on the front of your motor? Even then to break three brackets is unlikely.

Mike

 

[alldodge]

Yes. It is the motor. It happens in neutral and in gear.

When the engine is running the input drive shaft, top gears and lower shaft in the drive are always turning. So if the vibration is in the drive putting it in neutral does nothing but disengage the output prop shaft and prop.

That said, breaking your alternator bracket tells me you have an engine issue. Is there any play or roughness when the pulley is turned by hand?

 

[gm280]

The real question is, is the vibration causing the problems listed or vibration because of the broken parts? I certainly would check everything in the belt system. in fact I would also make sure the belt was the correct one for that setup. A too tight of a belt can apply a lot of force on things and cause issues as well. And with that stated, check your engine mounts. If they failed, your engine will most certainly vibrate all over the place and cause some really serious problems... JMHO!

 

[Redphone107]

Thanks for the input. I just went and saw an iron shop and they told me that they could repair it, but it would most likely break because its iron. He is fabricating an identical one out of 3/8" steel. AllDodge, I see what you are saying and so it very well could be something in the drive.

Watermann. I will try the seafoam this weekend. Here's another thought that you made me think of. When I changed the spark plugs, #4 had a spark plug insert on the plug that came out with the spark plug. Someone previously stripped the threads on the block hole and re-tapped the hole larger and put in a sleeve. I bought a new sleeve, put red RTV gasket seal on the outside and re-inserted it into the hole. Then tightened the plug down. I checked for any fluid to come out of the hole all weekend and it remained dry around the spark plug hole. Its going to be tough to try to check the compression with that sleeve in there. I have a compression tool, but I think the sleeve may come out again when I pull the plug. I had no idea that was done to the block when I bought the boat. If there was a loss of compression from an air leak around the plug, I should see gas or something coming out of the hole, right?

About the run-on. I am going to tweak the throttle cable and idle this weekend and see if that eliminates the run-on. Thanks for advice and any more thoughts are greatly appreciated.

 

[Watermann]

More than likely you would see carbon build up on or around the spark plug if it were leaking rather than fuel.

Good luck, I have my fingers crossed for ya.

 

[Redphone107]

Thanks, so yesterday I removed the plug and insert. The plug looked good and the hole looked good. Just for kicks, I ran a hole tap down the hole and it fit smooth. I blew the hole out for any metal shavings, covered the new insert with RTV, and reinstalled the plug. I have to wait 24 hours before cranking the engine so I will try it again tonight. I am suppose to get the steel bracket back from the shop tonight. I will post a picture of it. I looked at the carburetor last night. I can't adjust it for run-on until tonight when I crank it so we will see tonight.

 

[Redphone107]

So the bracket didn't come in today. Bummer. Quick question though. I am typing from phone so I cause any grammar errors. Would the timing Being off cause a vibration. I checked the timing not in base timing last week. I haven't had the chance to put it in base timing and test. Anyway the timing marker was about 1.25-1.5 inches left of the far left notch marker. I thought the timing marker on the harmonic balancer should be at 12 degree which should be at the end of the marker notch bar. It seemed like at idle the timing out of base timing was way to the left like 20 degree or something. I will test the timing in base timing this week but wanted yalls thoughts on timing causing vibration. Where are y'all's makers when not in base timing.

 

[alldodge]

Timing depends on your serial number
1 BTDC - Serial number break: 0L096999 and below
1 ATDC - Serial number break: 0L097000 - 0L0340999
2 ATDC - Serial number break: 0L341000 and above.

 

[Redphone107]

Mine is a 0M69XXXX so I think it would be 2ATDC. That should be just left of the 3rd mark. Now that would be in base timing, right? What about idling and not in base timing? I found this document that shows all the different ignition systems for the 3.0. I have the Delco distributor. Setting the base timing seems pretty easy. As soon as I get the bracket back and put the power steering pump on, I'm going to put it in base timing and see where the mark is then. I just don't think it should be so far to the left (outside the timing marker bar). The question is: would the timing being far out cause a huge vibration or would it just cause the engine to run rough. My engine does not really run rough and smooths out at higher RPMs.

 

[alldodge]

Page 13 of your pdf files shows where 2 ATDC, its the first mark below the 0
RPM is 650-700 in forward gear. Get it close, then take it out in the water and final adjust

If your engine is missing this can cause a vibration, but one so bad to brake a bracket is a bit much

 

[Redphone107]

No Title

Ok. So this is where I stand. The bracket worked out great. The guy really did a good job. The photos are posted below. The one on the left is the one he made out of steel. Boat ran ok at the lake. Yesterday when I got home, I worked on the timing. I really think that is the problem. I put it in base timing mode and set the timing to 2 degrees. It ran so bad I had to adjust the idle up keep it going. Before the adjustment the timing in base was around 8-10 degrees. After the adjustment it ran as crappy as before. I did find a sweet spot that smoothed it out at around 12 degrees BTDC, but that was in base timing so that worries me. It shouldn't run smoother at that setting. I put it back to 2 BTDC and left it. Is it possible that when someone was working on the boat previously that they installed the distributor wrong or set the timing chain wrong or did something that would cause the timing marker to be off? Why would it run better at such a far timing. When I revved it some after the adjustment to 2 degrees it still was vibrating. Here are a couple of questions for you gurus.

1. Does it hurt the boat to rev to 2,800 RPM with just a hose and ears hooked up? Does it need to be in the water to rev?

2. Should I take it to the lake, rev it to 2,800 rpm and just adjust the timing to make it smooth at high rpm. (with no timing gun attached). I guess this would just be timing it by sound and not the gun. Is that safe to do?

3. Does the air/fuel mixture have anything to do with this maybe? Should I try adjusting the air/fuel mixture, or can I really screw things up by doing that?

4. Why am I having to adjust the idle when adjusting the timing? Is that normal.


As always, thanks for your advice!!

 

[alldodge]

1. Does it hurt the boat to rev to 2,800 RPM with just a hose and ears hooked up? Does it need to be in the water to rev?

Should be 2 ATDC not BTDC, yes you can burn the impeller up running at 2800 rpm on a hose.

2. Should I take it to the lake, rev it to 2,800 rpm and just adjust the timing to make it smooth at high rpm. (with no timing gun attached). I guess this would just be timing it by sound and not the gun. Is that safe to do?

No timing is set a base timing and not while running at higher rpm.

3. Does the air/fuel mixture have anything to do with this maybe? Should I try adjusting the air/fuel mixture, or can I really screw things up by doing that?

Air fuel mix only deals with idle to about 1500 rpms, they have no effect above that

4. Why am I having to adjust the idle when adjusting the timing? Is that normal.

Adjusting idle when setting timing can happen if the previous owner did not set it correctly

 

[Redphone107]

That's for the answers. I did the timing tonight. I figured out why it wasn't working before. Most of the directions say to hook up the jumper wires and interrupt bypass before cranking. However I found one set of directions showing doing the jumper and bypass after cranking. That worked just fine. I did get the timing to 2 degrees after but had to crank the idle up as it wanted to die. Then when I disconnected the jumper and bypass it went to about 12-14 degrees before. It smoothed out some. I also played with the air/fuel screw and found a good spot where the idle was highest. The boat still shakes a bit. I am going to put a glass of water on the floor near the bilge and take a picture to post. I appreciate all the help. This is my first real boat that is not a fishing Jon boat so I am learning here. The next issue will hopefully be the last for a while. Runon. Is it pretty standard to have some run on if you cut the motor right after pulling someone on the tube. The only way I don't get run on is to idle the engine a minute or so after a pull. I don't mind idling it a bit but should I have to do that or should you be able to cut the motor right off after a pull without any run on?

 

[alldodge]

Run on or what most call dieseling is caused by Engine out of tune (plugs, cap, wires), poor fuel, timing set incorrectly or idle is to high