no compression in # 1 cilinder help

[bolo78910]

hello again guys HELPING A FRIEND AGAIN.

HE JUST BOUGHT A 1986 CARVER WITH A MERC 350 V 8 FRESH WATER COOL.

ON THE TEST RUN IS COULD NOT GO OVER 3000 RPM WITH A SS 17 PITCH PROP.

SO I LEND HIM MY 15 X 15 STELLITO SS PROP, THE RESULT IS THE SAME WITH BOTH PROP.

HE LOVE THE BOAT ANYWAY SO HE BOUGHT IT . I TOLD HIM TO DO A COMPRESSION TEST AND THE RESULT IS THIS,

120 ON ALL CILINDERS BUT NUMBER ONE HAS O COMPRESSION.

WHAT COULD CAUSE THAT . I WAS NOT THERE WHEN HE DOES IT , AND THAT WAS DRY TESTING HE DID NOT DO A WET TEST.

WHEN THE ENGING RUNS YOU COULD HEAR THE VALVE RATTLING.

ANY INFO WILL HELP THANKS

OUT

 

[Bt Doctur]

Re: no compression in # 1 cilinder help

If your hear rattling, time to pull a valve cover and take a look.broken push rod, stuck valve, pulled rocker arm stud.broken valve stem.

 

[Bt Doctur]

Re: no compression in # 1 cilinder help

If your hear rattling, time to pull a valve cover and take a look.broken push rod, stuck valve, pulled rocker arm stud.broken valve stem.If any of the above are present time to pull the head.

 

[rodbolt]

Re: no compression in # 1 cilinder help

with zero a wet test is a waste of time and oil.
its time to have a look at the valve train and most likly pull the head. stuck exhaust valves are common and usually wont clear the piston.

 

[bolo78910]

Re: no compression in # 1 cilinder help

up date guys he said al the plugs was foul with gas, i mean wet plugs thanks

 

[bosavy]

Re: no compression in # 1 cilinder help

you can also a clyinder leak down test just make sure u don't have a problem

 

[bruceb58]

Re: no compression in # 1 cilinder help

If he has zero compression, no need to do a leakdown test.

 

[rodbolt]

Re: no compression in # 1 cilinder help

nope with no needle motion its time to start opening it up. if it bent or damaged a valvetrain part its time to remove the head anyway.

 

[bolo78910]

Re: no compression in # 1 cilinder help

update, well we went to the boat today to check things out.

the #one cilinder that has no compression, has a problem .

the spring under the rocker arm is broken in two, so we went to a head rebuilder and he sold us one spring,

came back to the boat and install the it, try compression test again an now the cilinder has 150 compression i told my friend to re test all the others but he is one of them who love the short cut.

any way i test one more cilinder on the other side and got 125 with the cplate open wide, he has test it yesterday with the choke close..

i told him to do a wet test also but he said he dont think that nesisary. oh well thatv his boat iam only trying to help.

i have to pick up my daughter so i left him putting back the engine together .

he said he will call me with the starting result.

one last thing i notice the rocker arms make a lot of dent on the valve cover, it so bad that you could see it on the valve cover when install. seems the valve cover was install the wrong way or it is the wrong ones.

 

[bosavy]

Re: no compression in # 1 cilinder help

but that's the best way to find out what your taking apart.either your taking head off or hole in piston

 

[bolo78910]

Re: no compression in # 1 cilinder help

up date well last night test run goes like this . first engine sound goog no more rattling .

before the engine was not going over 3000 rpm now it goes up to 4000 but something is slipping because the the boat speed is not going with the rpm so i told him is either prop hub or coupler, so back to the marina we limp.

i got a back up prop on my boat so i install it on his boat,

marp this prop is not realy the right prop for alpha on,reason when fitted on it does not goes all the way in the lower unit housing.

so i know exhaust gas is escaping in little gap, when it sopose to escape through the prop rear.
anyway we still try the test, and she runs much more better, at 3000 rpm we got 15 miles per gps.

but it is cavitating a whole lot because of the wrong prop, i also notice a spark at the coil and i know spark is no good' so we replace the coil and a full tuen up .
plugs

wires

cap and roto

last the prop we took off was a ss and it has some real beat up i think he might runs grounds a lot .

NOW HEAR THIS , at the lower unit where the prop goes in has a big split/crack that can cause exhaust th excape so i know that a no no.

tonoght we wil do another test run after the full tune up .

thanks wil follow up.

 

[bolo78910]

Re: no compression in # 1 cilinder help

install the right prop and something is still slipping,

while at lno wake speed you can hear a loud coarse rubbing sound coming from the drivetrain area .

it would start out good then at about 3500 rpm it slip and not going no where., have to back off then it grab and start moving.

is this coupler or outdrive problem???

thanks for any info

 

[Don S]

Re: no compression in # 1 cilinder help

install the right prop and something is still slipping,

Was this a new prop of the correct size, or just another used prop.

while at lno wake speed you can hear a loud coarse rubbing sound coming from the drivetrain area .

Do you have the proper thrust hub on the prop shaft? Is the prop rubbing the housing?
May also be a bad gimbal bearing, or even gears in the drive, check the gear lube.

it would start out good then at about 3500 rpm it slip and not going no where., have to back off then it grab and start moving.

Could be prop, could be coupler. If it was a coupler, you would probably smell burned rubber when it was slipping.

 

[bolo78910]

Re: no compression in # 1 cilinder help

just another use prop don, that he got from the marina mechanic who sait it came of a alphaone drive.

he has two thrust washer both fits the same but one is wider that the other.

can you post a picture of the wright thrust washer for the alphaone drive thanks.

he jusy trying not to pull the boat antil november, but i told him he might have to pull it or something might get worse.

thanks

 

[Reel Poor]

Re: no compression in # 1 cilinder help

A note about the rockers hitting the valve covers. The rocker covers are on backwards. Turn them 180 degrees.

Thrush washers are not only designed to fit a particular drive but also a particular brand/design prop. Just because it fist the drive does not mean it will work with any give prop. Thrush washer usually come with a prop to fit the drive you specify, they don't come with the drive to fit the prop.

 

[Don S]

Re: no compression in # 1 cilinder help

A picture isn't going to help, the wrong one looks the same as the right one. When the prop is tightened down, does it hit the drive? Can it be tightened down completly and still turn?

If he just has another used prop, how does he know if it's good or not?
MIght try marking the prop and the hub, and run it and see if the marks move. If the do, then the hub is bad.

 

[bolo78910]

Re: no compression in # 1 cilinder help

with the rocker hitting the valve cover you are dead right on that .

the previous owner di have it on wrong we flip it around so that was solve ,thanks for that info realpoor.

don what is realy going on is when i go to mercstuff.com it shows how a prop sopose to fit snug to the lower unit housing, if not it will cause cavatitation

well these prop does not go in the housing snud when tighten , they still has a space in between,

money is kinda tight on him right now ,so when this weather breaks i will take my four blade from my boat and let him try it. he has the same alpha one drive as mines.

one last ?? so if the prop is not seated in the lower unit housing when tighten thats a no no ??


thanks guys so far the engine is purring like a kitten.

has power too something just slipping.

 

[Reel Poor]

Re: no compression in # 1 cilinder help

so if the prop is not seated in the lower unit housing when tighten thats a no no ??

If there is a gap between the gear case and the prop that exhaust can escape thru it will cause cavitation. May even feel like, "somethings slipping". Sound familiar ?

 

[bolo78910]

Re: no compression in # 1 cilinder help

oh man, you got to love this forum, pay attention guys.

i own my boat two years now, and i just reach my recomend wot rpm. 19 89 searay 220 5.7.

all the prop i was using was just getting me max rpm 4000 . 17 pitch 15 pitch.

now i finally get the wright prop for my alphaone it is a four blade 16 pitch, and you gess my wot rpm is now 4600 and can go a little more but i pull the throttle back, because i dont want to rev over the max rpm.

right now i know i need a 17 or 18 pitch to be safe.

so guys i hope we all learn from this , INSTALL THE WRIGHT PROP FOR YOUR DRIVE.


all those other prop that i tried non did fit all the way in the lower unit housing.

will let you guys know how we make out when i install my prop on my friend boat in the morning.

got to love this forum. thanks

 

[bolo78910]

Re: no compression in # 1 cilinder help

up date boat is fix.

ok guys the reason why the drivetrain felt like slipping .

was because of a dirty boat bottom.

haul it today and power wash the barnacles and slimes away.

took it for a run and got it up to 4000 rpm without slipping,

at 3500 rpm i got 23/24 miles per, gps . i did not trim out the drive or anything like that ,

i just use the trim tabs.

so thanks everyone with there input on this.

and to all others it is always good to post the fix on a problem so we can keep the learning going.


thanks again guys,
and clean those barnacles off might cause problems.