PCV valve/blow by issue

[karayj]

1989 Mark cruiser 3.7

So I have a video I’m hoping I can post. I did a compression test. and I’m gonna show her now because I have a blow by issue, but it might not be that bad kind of normal for a boat of my age. I did some wet test and dry test. I’ll show you the results there. My second question there is a little tube on the valve cover and a rubber hole goes on this tube towards the flame arrestor what is that tube for. Ax redirect that tubes somewhere else rather than attached to the flame arrestor because it’s thrown a lot of oily smoke into my carburetor which can’t be healthy after a while

And that goes to my second issue where I turn the mixture screw all the way in and the boat actually ran a little bit better, and the flame was loaded with an oily cakey film.

Wouldn’t turning in the mixture, screw all the way in caused the boat to stall out?

And my last scenario is that tube on the left side of the valve cover where the hose runs from that tube to the flame arrested. What is inside that tube? Is it some sort of PCV valve or just some tube to allow a hose to be attacked so I can go into the flame arrestor
I’m thinking of running a hose directly from that one of the vents on the side of the boat instead because it’s damaging the carburetor

Another question is do I replace the carburetor and exchange it for a new one or do I carburetor clean the crap out of it?

One thing I noticed is if I’m in gear idling at about 700 RPMs after about 25 or 30 seconds of running good she starts to sputter spit and then stall

 

[Scott06]

The compression numbers are fine. Start with cleaning the flame arrestor you will get some oil off the valve cover vent into the flame arrestor. Normally turning the idle mix screw in should stall the engine, unless the float bowl is over filling and spilling fuel into the bores. Would always rebuild the carb you have vs buying one rebuilt. No idea what you get back…. I use a ultrasonic cleaner from harbor freight to clean the carb parts good quality kit from mikes carb parts

 

[karayj]

The compression numbers are fine. Start with cleaning the flame arrestor you will get some oil off the valve cover vent into the flame arrestor. Normally turning the idle mix screw in should stall the engine, unless the float bowl is over filling and spilling fuel into the bores. Would always rebuild the carb you have vs buying one rebuilt. No idea what you get back…. I use a ultrasonic cleaner from harbor freight to clean the carb parts good quality kit from mikes carb parts

Thank you I was really worried about those compression numbers. Yaya got a replacement carburetor for an exchange. I convinced the guy that it must be leaking down. That’s why my valve cover gaskets stink the bloody hell. I’m really happy to hear about this. The new carburetors coming in on Wednesday I’m gonna throw it on the boat. What I find interesting though is when I put the carburetor on last year, the boat would start right up no problem without giving any gas but as I used it more and more by the fifth or six trip I’d have to wide open throttle to start. But I’m wondering if that smoke from the valve cover gasket was clogging things up and that’s why it made it more and more difficult to start .

 

[alldodge]

Agree compression numbers look good, but ... that depends on your gauge accuracy

Seeing 150 is great, but you have blow by, which means compression is blowing past the rings. Blowing past the rings means numbers should be lower.

The blow by is why you have so much build up on the flame arrestor (FA). The tube takes unburt pressure inside the block and moves it to FA so motor will suck it in and burn.

 

[karayj]

1989 Mark cruiser 3.7

So I have a video I’m hoping I can post. I did a compression test. and I’m gonna show her now because I have a blow by issue, but it might not be that bad kind of normal for a boat of my age. I did some wet test and dry test. I’ll show you the results there. My second question there is a little tube on the valve cover and a rubber hole goes on this tube towards the flame arrestor what is that tube for. Ax redirect that tubes somewhere else rather than attached to the flame arrestor because it’s thrown a lot of oily smoke into my carburetor which can’t be healthy after a while

And that goes to my second issue where I turn the mixture screw all the way in and the boat actually ran a little bit better, and the flame was loaded with an oily cakey film.

Wouldn’t turning in the mixture, screw all the way in caused the boat to stall out?

And my last scenario is that tube on the left side of the valve cover where the hose runs from that tube to the flame arrested. What is inside that tube? Is it some sort of PCV valve or just some tube to allow a hose to be attacked so I can go into the flame arrestor
I’m thinking of running a hose directly from that one of the vents on the side of the boat instead because it’s damaging the carburetor

Another question is do I replace the carburetor and exchange it for a new one or do I carburetor clean the crap out of it?

One thing I noticed is if I’m in gear idling at about 700 RPMs after about 25 or 30 seconds of running good she starts to sputter spit and then stall

View attachment 399943

I do have to say, though I posted the wrong numbers those are last year‘s numbers. I’m gonna try to attach this year‘s numbers.

 

[alldodge]

Again it's accuracy of the gauge, but the 115 dry is most likely where the major part of the problem is

 

[karayj]

1989 Mark cruiser 3.7

So I have a video I’m hoping I can post. I did a compression test. and I’m gonna show her now because I have a blow by issue, but it might not be that bad kind of normal for a boat of my age. I did some wet test and dry test. I’ll show you the results there. My second question there is a little tube on the valve cover and a rubber hole goes on this tube towards the flame arrestor what is that tube for. Ax redirect that tubes somewhere else rather than attached to the flame arrestor because it’s thrown a lot of oily smoke into my carburetor which can’t be healthy after a while

And that goes to my second issue where I turn the mixture screw all the way in and the boat actually ran a little bit better, and the flame was loaded with an oily cakey film.

Wouldn’t turning in the mixture, screw all the way in caused the boat to stall out?

And my last scenario is that tube on the left side of the valve cover where the hose runs from that tube to the flame arrested. What is inside that tube? Is it some sort of PCV valve or just some tube to allow a hose to be attacked so I can go into the flame arrestor
I’m thinking of running a hose directly from that one of the vents on the side of the boat instead because it’s damaging the carburetor

Another question is do I replace the carburetor and exchange it for a new one or do I carburetor clean the crap out of it?

One thing I noticed is if I’m in gear idling at about 700 RPMs after about 25 or 30 seconds of running good she starts to sputter spit and then stall

View attachment 399943

Agree compression numbers look good, but ... that depends on your gauge accuracy

Seeing 150 is great, but you have blow by, which means compression is blowing past the rings. Blowing past the rings means numbers should be lower.

The blow by is why you have so much build up on the flame arrestor (FA). The tube takes unburt pressure inside the block and moves it to FA so motor will suck it in and burn.

Yeah, I gave numbers from last year. I screwed up on the post and I can’t edit it. This is the actual numbers this year. Time to sell it ???

 

[karayj]

Again it's accuracy of the gauge, but the 115 dry is most likely where the major part of the problem is

Yeah, that’s what I was really concerned about that. I dropped 140 to 115. Now I just gotta decide what to do with this. I’d like to finish the season. I’m not a big fan of magic fluid. I don’t think that it always works to get the rings opened up again, but I might try something.

I think they started last year when I was running for a while, not realizing that my oil was contaminated with fuel thinning it out

 

[Scott06]

Yeah, that’s what I was really concerned about that. I dropped 140 to 115. Now I just gotta decide what to do with this. I’d like to finish the season. I’m not a big fan of magic fluid. I don’t think that it always works to get the rings opened up again, but I might try something.

I think they started last year when I was running for a while, not realizing that my oil was contaminated with fuel thinning it out

Yes 115 is getting very low. If you had fuel contamination with oil that isn’t good.

My 330 hr engine spits a fair amount of oil into carb top top but has great compression. I have typically seen more blow by in both my boats , and some oil in flame arrestor. Both these had good compression and ran well

In my opinion if it runs well but has some blow by leave it alone and run it . Either that or you are tearing it down.

Might be worth doing a leak down test

 

[karayj]

Yes 115 is getting very low. If you had fuel contamination with oil that isn’t good.

My 330 hr engine spits a fair amount of oil into carb top top but has great compression. I have typically seen more blow by in both my boats , and some oil in flame arrestor. Both these had good compression and ran well

In my opinion if it runs well but has some blow by leave it alone and run it . Either that or you are tearing it down.

Might be worth doing a leak down test

I did do a wet test ......the numbers declined in 1 year... I posted the wrong picture of the beginning of this feed. I’m gonna show you what it was last year and then what it is this year.

 

[karayj]

Well, I have an update. I found a guy that bought a block for spare parts and he really doesn’t need the block. I’m hoping to pick it up for $200. He paid five for it I guess. And I hear the dry wet numbers, which got me pretty excited. . Now we’re gonna go into the wonderful world of engine removal.

Will it engine hoist to the job if I lift the trailer up I don’t know unless I can use a backyard tree limb.

I know you have to take the drive off. I’ve done an engine before, but it was a V6. There’s a door that has to be removed to give me access to the rear engine and I’ll be a pain in the ass.

I’m not for another two weeks considering all the information how much time I have on this boat 567 more runs if I can use this boat more times and then take it off the end of August with the water is too cold. I’d be happy with that.

 

[Scott06]

Well, I have an update. I found a guy that bought a block for spare parts and he really doesn’t need the block. I’m hoping to pick it up for $200. He paid five for it I guess. And I hear the dry wet numbers, which got me pretty excited. . Now we’re gonna go into the wonderful world of engine removal.

Will it engine hoist to the job if I lift the trailer up I don’t know unless I can use a backyard tree limb.

I know you have to take the drive off. I’ve done an engine before, but it was a V6. There’s a door that has to be removed to give me access to the rear engine and I’ll be a pain in the ass.

I’m not for another two weeks considering all the information how much time I have on this boat 567 more runs if I can use this boat more times and then take it off the end of August with the water is too cold. I’d be happy with that.

If you repower consider putting in a 4.3 if you like the boat and want to keep it

The 3.7 was a bit of red headed step child for mercruiser if you go through the work get a newer better design 4.3

 

[matt167]

nothing wrong with a good 3.7l.. key point being a good 3.7L. It was a good idea with a few shortcomings that mercruiser abandoned because of the 4.3L

 

[karayj]

Adding a 4.3 requires re-fitting the engine compartment .... NOT DOING THAT. lol. 3.7 front engine mount 4.3 side mounts and exhaust refit to. NO way !!!

 

[karayj]

My next issues is a match or not I have a 0C520320 the engine block I am buying is a C460580. The seller is keeping the intake manifold /exhaust manifold /starter/ heater exchange . I hope my parts will fit on the new block.

 

[matt167]

They will, but I would recommend going through it before you run it.. and I wouldn’t pay much. If you are up to bullet proofing it. Add an aluminum head. It needs to have BBF ports as some aftermarket BBF heads come with BBC exhaust ports… but you put an aluminum head on it, you’ll have better performance and itll not give head gasket problems.. the cups for valve adjustment will need to be checked. I’m not sure if all 470s used that style cup adjustment pocket

 

[karayj]

They will, but I would recommend going through it before you run it.. and I wouldn’t pay much. If you are up to bullet proofing it. Add an aluminum head. It needs to have BBF ports as some aftermarket BBF heads come with BBC exhaust ports… but you put an aluminum head on it, you’ll have better performance and itll not give head gasket problems.. the cups for valve adjustment will need to be checked. I’m not sure if all 470s used that style cup adjustment pocket

Im paying 300 / I ran it and compression passed Dry and wet