Cylinders Low In PSI ? (HELP)

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

Im wondering, what made you do the comp test in the first place? Loss inperformance? Rough idle? And why do you have such big boats? Small boats are simpler. Yes the test with the air compressor will work, what you wana do is get the cyl your testing on tdc or a little past, then when you add air the pressure will rotate the engine over to bottom dead center, to ensure your valves arnt open.

The boat ran rough and burned alot of fuel. Was not achieving its speed like before.

 

[achris]

Re: Cylinders Low In PSI ? (HELP)

Im wondering, what made you do the comp test in the first place? Loss inperformance? Rough idle? And why do you have such big boats? Small boats are simpler. Yes the test with the air compressor will work, what you wana do is get the cyl your testing on tdc or a little past, then when you add air the pressure will rotate the engine over to bottom dead center, to ensure your valves arnt open.

Doesn't matter why... We are where we are.. He's got compression problems, let's just fix one thing at a time, and not drag the past up, it just adds a bit of confusion, and that's about the last thing we need right now....

The piston needs to stay at TDC during the leakdown test, not be flicked to BDC.... Remember that at BDC after the firing stroke, the exhaust valve opens....

Chris.......

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

Watching the video... I'll make comments as I'm watching, so they may be a little disjointed...

1. Makes no difference between removing the heads to replace the head gaskets and removing the heads to have them worked... Exactly the same amount of work for you.
2. Your compression gauge is fine... ($40 is not a lot for good tools...)
3. Inside the tube is a SCHRADER valve. (car tyre valve)
4. Water squirting out when cranking.... You're right about that one. Another possible cause of high pressure could be carbon build-up...
5. Leave the other threads until later... It could lead to a lot of confusion with multiple threads running at the same time... Do one thing at a time and do it properly..
6. Correct about the timing marks and getting the cylinders to TDC... Firing order is 1-8-4-3-6-5-7-2
7. Rule#1 about boats and money. You will never get all the money you put into a boat back... Accountants call this a 'liability'. If you want an asset, buy a house....
8. You'll be replacing the head gaskets anyway. They are 'single use' parts.... always... Gaskets can't and should never be reused.
9. Head bolts need a 5/8" socket.
10. I suggest using a 1/2" drive set for working on these engines.
11. Get yourself a brickies wooden float and put a length of fine emery cloth along the bottom. Makes cleaning gasket surfaces easier... Same with a 1-1/2 or 2" wood chisel.
12. DO YOU HAVE THE GENUINE SERVICE-MANUAL????

Chris.....

Yea I have the service manual. And thanks for the tips. Well when i find out what needs to be done then i will for sure replace all the seals and gaskets. Nothing a hundred dollar bill would not fix. Wish me luck!!!

 

[xjdriver]

Re: Cylinders Low In PSI ? (HELP)

The boat ran rough and burned alot of fuel. Was not achieving its speed like before.

Ok, not trying to be a di## or nothin but i would suggest having a mechanically inclined buddy there to help you thru the top end work. Dont take much tools to pull heads off a 350, but as achris said your gona want a 1/2 inch drive and a manual.you really got 2 big cruiser style boats? And you look like 19, must have a good job, or own a gas station, lol

 

[achris]

Re: Cylinders Low In PSI ? (HELP)

Yea I have the service manual. And thanks for the tips. Well when i find out what needs to be done then i will for sure replace all the seals and gaskets. Nothing a hundred dollar bill would not fix. Wish me luck!!!

Once you have the heads off and know what you're looking at, best to buy a 'top overhaul' kit. It has all the gaskets and seals in it. Probably the best place to get one will be the machine shop you choose. They can supply the kit and use the valve stem seals from it....

Also get yourself a tap to clean the head bolt threads in the block. From memory, it's a 1/2" UNC. You MUST clean the holes up before you put the head bolts back in, and use some thread sealer (like loctite 567) on the threads to seal them. They go straight into the water jacket and if you don't seal them, water will leak up the bolt shaft and contaminate the oil....

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

Ok, not trying to be a di## or nothin but i would suggest having a mechanically inclined buddy there to help you thru the top end work. Dont take much tools to pull heads off a 350, but as achris said your gona want a 1/2 inch drive and a manual.you really got 2 big cruiser style boats? And you look like 19, must have a good job, or own a gas station, lol

Naa i am almost 21 LOL. Still in collage. But yea i work at a website engineering firm as part time almost 7 days a week and they pay really good money. And i understand where you are coming from because if i F*** up while doing this then the next time i will really brake my engine and that when i bust out another 10k LOL.

 

[xjdriver]

Re: Cylinders Low In PSI ? (HELP)

Doesn't matter why... We are where we are.. He's got compression problems, let's just fix one thing at a time, and not drag the past up, it just adds a bit of confusion, and that's about the last thing we need right now....

The piston needs to stay at TDC during the leakdown test, not be flicked to BDC.... Remember that at BDC after the firing stroke, the exhaust valve opens....

Chris.......

Hes not really doing a leak down test, i dont think its gona stay at tdc with 60psi on top, but i could be wrong, at bdc shouldnt both valves still be closed?

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

Ok, not trying to be a di## or nothin but i would suggest having a mechanically inclined buddy there to help you thru the top end work. Dont take much tools to pull heads off a 350, but as achris said your gona want a 1/2 inch drive and a manual.you really got 2 big cruiser style boats? And you look like 19, must have a good job, or own a gas station, lol

And i really did not chose to have 2 big cruisers. My dad gave me this one when i was 17 and bought himself the baha and then gave me that one when i was 19 and had my capt license to run his charter business in the summer time. But my parents own there private marina so i have no expenses for docking and thats where that money goes! LOL

 

[tpenfield]

Re: Cylinders Low In PSI ? (HELP)

Hes not really doing a leak down test, i dont think its gona stay at tdc with 60psi on top, but i could be wrong, at bdc shouldnt both valves still be closed?

No . . . valve overlap will have them slightly open. Same as on TDC of the exhaust stroke.

In practice you need to be within a few degrees of rotation of TDC on the compression stroke for the leak test. The piston has no leverage on the crankshaft at TDC., so it won;t turn. A few degrees off won't be enough to turn the engine. . . . 5-10 degrees . . . different story.

 

[achris]

Re: Cylinders Low In PSI ? (HELP)

Hes not really doing a leak down test, i dont think its gona stay at tdc with 60psi on top, but i could be wrong, at bdc shouldnt both valves still be closed?

No . . . valve overlap will have them slightly open. Same as on TDC of the exhaust stroke

Thanks Ted...

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

Once you have the heads off and know what you're looking at, best to buy a 'top overhaul' kit. It has all the gaskets and seals in it. Probably the best place to get one will be the machine shop you choose. They can supply the kit and use the valve stem seals from it....

Also get yourself a tap to clean the head bolt threads in the block. From memory, it's a 1/2" UNC. You MUST clean the holes up before you put the head bolts back in, and use some thread sealer (like loctite 567) on the threads to seal them. They go straight into the water jacket and if you don't seal them, water will leak up the bolt shaft and contaminate the oil....

Ok will do! I will buy everything you tell me! Based on your recommendation. You sound like a person with a lot of experience!
Chris you own any boats yourself? LOL

 

[tpenfield]

Re: Cylinders Low In PSI ? (HELP)

Thanks Ted...

You're welcome, Chris

Let's get this leak test over with, before we have 10 pages of speculation

 

[xjdriver]

Re: Cylinders Low In PSI ? (HELP)

No . . . valve overlap will have them slightly open. Same as on TDC of the exhaust stroke.

In practice you need to be within a few degrees of rotation of TDC on the compression stroke for the leak test. The piston has no leverage on the crankshaft at TDC., so it won;t turn. A few degrees off won't be enough to turn the engine. . . . 5-10 degrees . . . different story.

Ok cool thanks for the info, ive done alot of compression tests, not so many leak downs.

 

[achris]

Re: Cylinders Low In PSI ? (HELP)

...Chris you own any boats yourself? LOL

Yes... My current boat is in my signature... (and it's on it's third engine :facepalm

In the past, a 15' runabout that started life with a 150hp outboard that would top out at over 60mph... A small ali boat with a 15hp... I've also skippered many much bigger boats for friends... I'm also getting the wife use to the idea of a 28' Bertram flybridge... That's a couple of year down the road though...

I also owned a boat shop in the 90s (and was chief mechanic), so was in and out of boats all day. We did many re-powers, so I got experience in so many different boats... We would take all new engines out on the water and run them to ensure they had the right propeller on...

I also grew up with boats, my father building 4 of his own... I was almost born on one of them....

 

[achris]

Re: Cylinders Low In PSI ? (HELP)

Let's get this leak test over with, before we have 10 pages of speculation

Amen to that!

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

You're welcome, Chris

Let's get this leak test over with, before we have 10 pages of speculation

For sure !!!

 

[achris]

Re: Cylinders Low In PSI ? (HELP)

Yea I have the service manual. And thanks for the tips. Well when i find out what needs to be done then i will for sure replace all the seals and gaskets. Nothing a hundred dollar bill would not fix. Wish me luck!!!

When you take the heads to the machine shop and purchase a 'top overhaul' set, be sure he understands it's a marine engine. The head gaskets need to be composite or SS, not steel. One of the commonly used sets is FelPro 17214. That set gives you the head gaskets, valve cover gaskets, intake and exhaust manifold gaskets and all the valve stem seals...

Chris.......

 

[Gator1996]

Re: Cylinders Low In PSI ? (HELP)

Is this guy for real?I hate to be negative nancy here but Bigdog is taking you guys for a big ride. I don't think its cool that someone would take advantage of the good nature of this board by BSing his way through a thread.

So which is it? The Baha is dad's for business or he gave it to you? Parents own a marina and you slip your boat for free but you launch it from a public ramp on video? Marina in the family but you don't have access to resources and tools to get this work on the road? Captain's license, charter business, the list goes on! I'm gonna have to call BS. Are you the same guy that posted bogus pictures of his motor?

What purpose does it serve to string the guys along that are trying to help you?

And the funny thing is this dude is answering others' questions on other threads. Really?

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

Is this guy for real?I hate to be negative nancy here but Bigdog is taking you guys for a big ride. I don't think its cool that someone would take advantage of the good nature of this board by BSing his way through a thread.

So which is it? The Baha is dad's for business or he gave it to you? Parents own a marina and you slip your boat for free but you launch it from a public ramp on video? Marina in the family but you don't have access to resources and tools to get this work on the road? Captain's license, charter business, the list goes on! I'm gonna have to call BS. Are you the same guy that posted bogus pictures of his motor?

What purpose does it serve to string the guys along that are trying to help you?

And the funny thing is this dude is answering others' questions on other threads. Really?

Ok , I understand. Thanks again:joyous:

 

[Gator1996]

Re: Cylinders Low In PSI ? (HELP)

The issue is that I have read through the whole thread, maybe you should too! Then at least your story may be consistent.

Personally, I am looking away from the train wreck. Carry on my friend, I wish you luck in your endeavors.
Gator