How to get to the crank shaft the easiest way ?

[MercBlackMax1]

Hey just got my boat back in the drive way and took the heads of my pistons. They are fully lubed up and no rust + no scoring in the block and i have 120psi on all. I can turn the fly wheel and everything moves good untill i block at somepoint but i can force it through.

I was wondering what could be happening to do this. Im guessing either a bent crank or a bent piston arm.
I want to take the motor off but i dont want to touch the carbs. can i change the crank shaft or arm in my drive way and if so where do i go from taking the flywheel off.

thanks

 

[Chris1956]

Re: How to get to the crank shaft the easiest way ?

You will need to pull the powerhead off the midsection to get to the crankshaft. Do you know why the crank was damaged? You will need to fix the underlying cause, and since all lubrication of the motor goes thru the carbs, it is likely you will need to touch the carbs.

 

[MercBlackMax1]

Re: How to get to the crank shaft the easiest way ?

You will need to pull the powerhead off the midsection to get to the crankshaft. Do you know why the crank was damaged? You will need to fix the underlying cause, and since all lubrication of the motor goes thru the carbs, it is likely you will need to touch the carbs.

hey thanks for your replay , this is what happend i bought the boat last winter and i finally got to try it out last weekend . my first run went ok i brought the boat up to 60 mph for a good 10 15 minutes i brought it back to the dock and parked it everything went ok. i went out about 3 hours later and punched it againg from 30 mph to 60 and everything just siezed up. my temp over heated to 240 f. After being toed back to the dock the motor fired back up but with a wierd noise in the motor.

I dunno what i did?

 

[CharlieB]

Re: How to get to the crank shaft the easiest way ?

First, drop the gearcase to see it you can now turn the motor freely, if so you have a gearcase problem.

If no, then the powerhead needs to come off and apart.

 

[Chris1956]

Re: How to get to the crank shaft the easiest way ?

You likely suffered from lean fuel mix, overheating, over advanced timing or some combination of all three. As was advised, drop the gearcase and see if that is it. If not, you may have thrown a rod, and the motor will need a complete tear-down to determine if it is fixable.

In anycase, overheating is real bad and will cause severe engine damage. That must be addressed also.

 

[MercBlackMax1]

Re: How to get to the crank shaft the easiest way ?

You likely suffered from lean fuel mix, overheating, over advanced timing or some combination of all three. As was advised, drop the gearcase and see if that is it. If not, you may have thrown a rod, and the motor will need a complete tear-down to determine if it is fixable.

In anycase, overheating is real bad and will cause severe engine damage. That must be addressed also.

The motor turns freely by the flywheel with the lower unit still on for the over heating my water pump would take about thiry seconds before it would **** but it was working. on my second run i didnt check and it must have been not working or somthing.

when i turn the fly wheel all the pistons are turning smooth and then block, if i turn ccw and then back cw it wont block and i can turn it full 360 with no blocking but then it blocks again.

also my piston housing has no damage on all the cylinders so i must have bent a rod but i dont uunderstand how thats even possible.

 

[MercBlackMax1]

Re: How to get to the crank shaft the easiest way ?

First, drop the gearcase to see it you can now turn the motor freely, if so you have a gearcase problem.

If no, then the powerhead needs to come off and apart.

i see what you mean if i can turn it without the foot on freely with no blocking then my problem is in the foot, but when its in gear the prop locks up and when its in reverse the same thing leading me to believe there is no problem with the gears.

 

[MercBlackMax1]

Re: How to get to the crank shaft the easiest way ?

i see what you mean if i can turn it without the foot on freely with no blocking then my problem is in the foot, but when its in gear the prop locks up and when its in reverse the same thing leading me to believe there is no problem with the gears.

Dude i owe you a f-ing beer your a genius i dropped the foot and guess what the moter turns with my pinky. im so happy you told me to do that thanks alot!! going to go buy a used foot right this instant!

 

[Chinewalker]

Re: How to get to the crank shaft the easiest way ?

I would still do a compression check. You said it overheated. If the boat is new to you, a compression check is ALWAYS a good thing to start with to give you a baseline reading should anything happen later...

 

[MercBlackMax1]

Re: How to get to the crank shaft the easiest way ?

I would still do a compression check. You said it overheated. If the boat is new to you, a compression check is ALWAYS a good thing to start with to give you a baseline reading should anything happen later...

Hey thanks i did a compression test yesterday i have 120 on all cyls from what ive seen on here thats about right?

 

[Chris1956]

Re: How to get to the crank shaft the easiest way ?

Seems you have had some good luck. Rebuild the waterpump on the new gearcase and test the thermostats and poppit valve. Run the motor a while and check the color of the spark plugs. They should be light to medium brown, if the mixture is right.

 

[MercBlackMax1]

Re: How to get to the crank shaft the easiest way ?

diffently will rebuild the water pump although this one seems ok no gasket damage and impeller looks ok just a but stiff to turn.
how do i check the thermostat and why? and the poppit valve is for the fuel right? my efi is cancelled i mix 50:1 raitio. also last question do i have to tourque tighten the heads or just go by hand?

 

[Silvertip]

Re: How to get to the crank shaft the easiest way ?

Dude -- you had an overheat. The thermostat is one of the items that controls engine temperature. Same for the poppet (bypass) valve. And you cannot tell by looking at the water pump if it is ok. You have the unit apart. Replace it. A thermostat that is stuck shut causes overheat at idle and slow speed. A defective bypass valve causes overheat at high speed if it is stuck shut. Overcooling at idle and slow speeds if it is stuck open. These parts are dirt cheap when compared to an engine rebuild.

 

[MercBlackMax1]

Re: How to get to the crank shaft the easiest way ?

Dude -- you had an overheat. The thermostat is one of the items that controls engine temperature. Same for the poppet (bypass) valve. And you cannot tell by looking at the water pump if it is ok. You have the unit apart. Replace it. A thermostat that is stuck shut causes overheat at idle and slow speed. A defective bypass valve causes overheat at high speed if it is stuck shut. Overcooling at idle and slow speeds if it is stuck open. These parts are dirt cheap when compared to an engine rebuild.

ok sounds like a good idea! where is the thermostat located. The water pump will be changed for sure and ill take a look at the poppit but i dont really know what to look for? what does the bypass valve do?

 

[MercBlackMax1]

Re: How to get to the crank shaft the easiest way ?

ok sounds like a good idea! where is the thermostat located. The water pump will be changed for sure and ill take a look at the poppit but i dont really know what to look for? what does the bypass valve do?

Jesus! thos thermostats where FINISHED nothing left crusted white and no more seal absolutly disgusting thanks im gonna change those and the water pump. like i said the peppet valve im dunno what to look for! thanks alot Matt.

 

[Jlawsen]

Re: How to get to the crank shaft the easiest way ?

my temp over heated to 240 f.

No Black Max ever comes away from that unscathed. There is some damage, you just haven't found it yet.

when i turn the fly wheel all the pistons are turning smooth and then block, if i turn ccw and then back cw it wont block and i can turn it full 360 with no blocking but then it blocks again.

It's impossible to do a compression test in this condition. Your compression prior to your overheat is no longer valid.

Now seriously, pull the heads and have a look. #2 likely has some serious aluminum errosion on the exhaust side and likely all around the top edges. Most likely you've got aluminum built up in the ring lands and a ring is hanging in one of the ports.

Take some pic's of the cylinders and post them. If it's just one or two cylinders there's a good chance it can be fixed without removing the powerhead. You do have to remove the intake but the carbs can stay on the intake.

 

[MercBlackMax1]

Re: How to get to the crank shaft the easiest way ?

No Black Max ever comes away from that unscathed. There is some damage, you just haven't found it yet.




It's impossible to do a compression test in this condition. Your compression prior to your overheat is no longer valid.

Now seriously, pull the heads and have a look. #2 likely has some serious aluminum errosion on the exhaust side and likely all around the top edges. Most likely you've got aluminum built up in the ring lands and a ring is hanging in one of the ports.

Take some pic's of the cylinders and post them. If it's just one or two cylinders there's a good chance it can be fixed without removing the powerhead. You do have to remove the intake but the carbs can stay on the intake.

Honestly i think they might be ok ill post the pics of them today sometime but i think im good everything it working properly in the power head now that the foot is off i broke a gear in the foot witch was causing the blocking i see no scoring in the block what so ever and i did mmy compression test with the foot off and like i said 120 in all cylinders. I did take the heads off the cylinders and they looked perfect i can turn the fly wheel with my pinky and its really smooth.

 

[MercBlackMax1]

Re: How to get to the crank shaft the easiest way ?

Dude -- you had an overheat. The thermostat is one of the items that controls engine temperature. Same for the poppet (bypass) valve. And you cannot tell by looking at the water pump if it is ok. You have the unit apart. Replace it. A thermostat that is stuck shut causes overheat at idle and slow speed. A defective bypass valve causes overheat at high speed if it is stuck shut. Overcooling at idle and slow speeds if it is stuck open. These parts are dirt cheap when compared to an engine rebuild.

hey man my thermostat is missing the hole spring section? where the hell did it go cant just dissapear.

 

[Chris1956]

Re: How to get to the crank shaft the easiest way ?

Poppet valve is located on the base of the block, starboard side. It will have two or four bolts, depending on the year of the motor. Rebuild that mother....

 

[MercBlackMax1]

Re: How to get to the crank shaft the easiest way ?

Poppet valve is located on the base of the block, starboard side. It will have two or four bolts, depending on the year of the motor. Rebuild that mother....

hey thanks i found it yesterday i was just confused because i saw one on another motor that was a figure 8 my poppet seems ok ? the spring works and it seems to move freely up and down. I took off where the water goes to cool down the motor from the thermostat to try and find the rest of the t stat but its no where to be found? also busted 4 siezed bolts had to drill them out and retap them at work. this isnt getting any easier. once i get my gaskets for the two heads and the two other covers ill work on getting myself another foot! already got one at the marina that might fit but the girls telling me my serial number checks out as a 200 hp witch makes things complicated for parts.