(UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

[franticmotionz]

Ok, so I've been working on this motor for like 2 months heavy, cannot figure it out. It's a mid-60's Merc 950ss with a thunderbolt ignition. It is loud and rediculously powerfull in neutral, but in the water in gear it won't move my boat passed 8mph on the gps. I've rebuilt the carbs, the fuel pumps, put in new plugs. She starts up as good as any old merc cold. In neutral she sounds great but in gear she has nothing. Here is whats going on.

Idle's low and cuts off after I've run it a few minutes when I stop, but then starts right back up again with out having to pump bulb.

When I'm moving I can hear little changes in the way she sounds but the speed doesn't change. Like rpms raise up just a hair and then go back down.

In neutral the throttle is responsive and motor sounds GREAT. Any idea what I can do, I know the motor will run.

I've checked the compression now and it reads like this:

1-40
2-40
3-43/45
4-45
5-33/35
6-30/35

Please someone give me a clue, I'm dieing here!!!!!

 

[franticmotionz]

compression 1/40-2/40-3/43-4/45-5/35-6/33

compression 1/40-2/40-3/43-4/45-5/35-6/33

Please possable problems and solutions.

Definites a plus!!!!!!!!!!!!!!

it's a mid 60's merc 950ss in-line 6

 

[Blk-n-Blu]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

If the RPMs are rising while you are accelerating in gear and in the water you may have a "spun prop hub" the rubber bushing which keeps the prop engaged to the propshaft. Try another prop.

 

[ChrisfromVT]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

Looks like a bad compression issue based on those numbers. Compression should be checked before anything else. Those numbers should be up over 100psi

 

[ajgraz]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

Agreed compression numbers sound very low...though consistently very low across all cylinders, strange--to my knowledge, typically only one or two (adjacent) cylinders would be so low in a "blown" motor.

Are your units psi?
What kind of compression tester are you using?
Are you letting it cycle at least four or five full revolutions before recording a pressure reading?
When was the motor last run? (Cold and no oil lubing the cylinders will give low readings)

 

[franticmotionz]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

It was last run last weekend, I put it in the water after I rebuilt the fuel pumps and carbs. I thought that may have been the problem.

I don't think the prop is spun because when it has load is when it doesn't run right. If the prop was spun it's my understanding the rpms would rev up but the boat wouldn't go. When it's in gear it's fighting for revs.

The units for the compression test are in psi. I used a new fresh out of the packege OEM compression tester, and turned it over till the needle wouldn't move anymore.

Just out of curiosity, would a head gasket be an issue that would cause all the cylinders to be in the same range and could build up and deposits in the cylinders be hindering the pistons movement enough to cause the pistons to be a little sluggish. That would drop compression wouldn't it.

 

[JB]

Re: compression 1/40-2/40-3/43-4/45-5/35-6/33

Re: compression 1/40-2/40-3/43-4/45-5/35-6/33

Much lower psi than I would expect from a correctly done compression test, and the variation is far too great.

I think you did a test incorrectly or you had a dry engine that hasn't been turned over in decades.

Go to the Engine FAQs. Crank her up, warm her up, then do a test as described there.

Let us know what you get that time.

 

[JB]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

It sure is annoying to find the exact same question twice, FM.

Please read this: http://forums.iboats.com/showthread.php?t=250877

And don't double post any more.

 

[cannonford57]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

kinda suprising with numbers that low the engine even runs.can ya try another gauge?you wouldnt be the first to get something faulty right outta the box.

 

[Bob_VT]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

When it's in gear it's fighting for revs.

The units for the compression test are in psi. I used a new fresh out of the packege OEM compression tester, and turned it over till the needle wouldn't move anymore.

Just out of curiosity, would a head gasket be an issue that would cause all the cylinders to be in the same range and could build up and deposits in the cylinders be hindering the pistons movement enough to cause the pistons to be a little sluggish. That would drop compression wouldn't it.

Have you done a link and synchronization of the carbs and timing? How about a complete de-carb? Do you have a manual? I doubt the head gasket is blown....your motor does not have a head gasket.

 

[verado7]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

a prop will slip occasionally but it wont necessarily slip so much that you cant get going - but beyond all that - you need to rebuild that motor first - it barely has enough compression to idle properly . 100 psi is on compression is more or less a cut off point to nearing rebuild .

 

[stubbstheman88]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

this is just an idea that may be wayyy out of the ballpark where u need to work but... i had a motor once that the fill plug for the lower unit grease came out and the motor sat awhile with no lube.. we tried to run it but it kinda did the same thing.. there was so much rust and corrosion down in the lower unit that it coulod barley turn with the tourqe of the engine... just an idea

 

[CharlieB]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

Compression #'s must be waaaay off!

I seriously doubt that a motor would even start with #'s that low, even spun with 24 V and using straight ether. (Do NOT try that)

The fact that the motor runs at all shows some hope.

Pull the plugs and look at them, WHICH ones are still CLEAN?

Test each plug wire for spark using an adjustable gap tester or build a tester with a block of wood and a couple of nails.

You NEED to be sure that all cyl's are capable of arcing a bright blue hot 'crack'.

A couple of dead cyl's will sound fine on the hose and rev like crazy, yet fail to turn a prop once in the water.

 

[sonoramike]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

surprised that it runs at all with those compression numbers. you're wasting money by continuing to throw parts at it without figuring out why the compression is so low. as others have noted you should be over 100 in all cylinders and less than 15% difference max between highest and lowest values.

Just out of curiosity, would a head gasket be an issue that would cause all the cylinders to be in the same range and could build up and deposits in the cylinders be hindering the pistons movement enough to cause the pistons to be a little sluggish. That would drop compression wouldn't it.

sorry, have to chuckle at this - carbon hinder the pistons movement?? compression is a function of the rings ability to seal the cylinder on the up stroke. assume piston crowns are intact since you have some compression, but it looks like you have massive ring failure of some sort. has the engine been rebuilt? did you hone the cylinders? are the cylinders seized? what do the plugs looks like?

 

[franticmotionz]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

plugs are all clean, it's an interesting case I know. I'm not an expert by any means but I have a good skill set when it comes to working through problems. I shall continue to pluck through all of the help you guys have given me. Keep the suggestions coming. Tomarrow I'm gonna put it back in the water, run it for a spell and check the compression again. Then I'm gonna take the foot off and see what condition it's in. I will also check to see if the prop is spun or the wires are arching.

Thanks again, keep it coming!!!!!!!!!!!!!!!!!!!1

 

[sonoramike]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

Then I'm gonna take the foot off and see what condition it's in. I will also check to see if the prop is spun or the wires are arching.

none of those things are going to resolve your compression issue. you can run around chasing various issues like prop and wiring and whatever else but that motor isn't going to run until you figure out what the compression problem is.

me? I'd try a different compression gauge, if the readings are still the same then I'm plling all the plugs and sticking a light down the cylinders to see what they look like. If they look decent enough and I can still see cross hatch on the walls then the barrels are coming off and I'm grabbing my mic and measuring pistons and cyl diameters, and my feeler gauges for ring gap. that's going to tell me what I need to know.

This motor use a head and head gasket, or is it one of the models that has the cylinders and heads as one unit? I have a 650 with the one piece cyl and heads

 

[sonoramike]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

plugs are all clean

I'm not sure you could be less specific if you tried... "clean" when it comes to 2 stroke plugs is not a good thing. if by clean you mean "white and shiny" then you've got a lean condition

can you post a photo of a plug?

 

[Chinewalker]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

DO NOT remove the cylinder "head". It's not a head, it's a water jacket. This motor has cast-in domes for the cylinders and does not have a removable cylinder head.

I concur - before doing ANYTHING else, confirm the compression numbers with another gauge. That motor will not run on the numbers given, so something is out of whack.

- Scott

 

[sonoramike]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

guess he got the problem fixed....

 

[sschefer]

Re: (UPDATE)Ahahaahahahahahragarg explative!!!!!! Help!(UPDATE)

The compression test is wrong. Like CharlieB say's 35-45lbs of compression will not support ignition. The motor starts and revs so reeds are probably still intact. It doesn't run under a load. I'm guessing ignition or fuel pump.. Maybe we'll never know.