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View Full Version : 1990 Prostar, 350 engine w/only 2 valve compression


SkiinJ
06-05-2007, 04:48 PM
Upon taking our boat, a 1990 Prostar, with a 350, in for a tune up and have some bad gas flushed out, we got the grim news that only 2 valves are giving any compression and we supposedly need a new engine. We brought the boat back home, it doesn't run at all and we are boatless for the summer. What does one do if they don't know anything about engines?:(

JKTX21
06-05-2007, 05:01 PM
Hmmm, some new heads might keep you running a little longer. Wait for JimN to respond, he'll have some good advice.

JimN
06-05-2007, 05:21 PM
I don't know.:confused:

Prostar Rich
06-05-2007, 05:26 PM
Upon taking our boat, a 1990 Prostar, with a 350, in for a tune up and have some bad gas flushed out, we got the grim news that only 2 valves are giving any compression and we supposedly need a new engine. We brought the boat back home, it doesn't run at all and we are boatless for the summer. What does one do if they don't know anything about engines?:(

Did you mean only 2 cylinders have compression?

Prostar Rich

JimN
06-05-2007, 05:40 PM
Seriously, if you took it in for a tune-up, I have to assume it ran before that. Who did you take it to, what did you have them do, other than a tune-up and how are they explaining the fact that it no longer runs at all?

If it definitely ran before they got it, it should run when you get it back, regardless of how well.

The first thing I would do is talk to the service manager about the condition pre/post service. Don't get into a technical peeing match and if that's all he wants to do (talk over your head), ask to talk to the GM or owner. Just ask why it doesn't run at all now, don't get into the fine details. It could be as simple as the tech attaching the plug wires on a GM, in the Ford pattern. If it's a '90, I thought they all had 351 motors, except for the big block. Seeing 350 and being in "350 mode" while working on a 351 can be a problem and vice-versa.

Next, I would call around and ask how much an estimate costs, and tell them what the situation is. The main things that need to be done are:

1) Check for spark, both intensity & consistency and correct timing/firing order
2) Check for fuel quality and pressure- this should be self explanatory
3) Compression/leakdown/vacuum test- this indicates the general health of the motor because if the valves and/or rings are bad, the gauges will indicate low compression and any pressure in the cylinders will leak down rapidly. Bad gaskets can also be an issue here but they don't cost as much in labor as machining/rebuilding. If the vacuum is bad, the air/fuel charge will be less than what it should be and the fuel liquid won't atomize the way it should.

If you get an estimate (all of the above work should take less than 2 hours, even with warming the motor up), post it here. Have them itemize everything they did to decide what the motor needs.

How long have you owned this boat and what is the service history? If it hasn't been tuned up in a long time or isn't used much, it could be bad fuel, clogged fuel lines, gummed up carb, etc. If the spark is non-existent, there is always a reason. If the compression and vacuum are low, it's not the end of the world. If the motor froze, overheated or was generally abused, it could get expensive but even then, the worst case is replacing the motor, assuming all else is operational.

TMCNo1
06-05-2007, 05:42 PM
A Indmar 350 GM/Chevy option was available in '87 to '93 at an additional cost of $750+/-.

Trade it for as Hang Glider real quick!

JimN
06-05-2007, 05:44 PM
JKT- who are you callin' a new head?

Jim@BAWS
06-05-2007, 05:50 PM
Upon taking our boat, a 1990 Prostar, with a 350, in for a tune up and have some bad gas flushed out, we got the grim news that only 2 valves are giving any compression and we supposedly need a new engine. We brought the boat back home, it doesn't run at all and we are boatless for the summer. What does one do if they don't know anything about engines?:(


First of all is it a FORD 351...more than likely it is. If the distributer is in the front of the motor closet to the ski pylon it is a FORD.

If it is a Chevy the distributer is on the back of the motor.

Compression should be between 110 and 125 with in 10% on all cylinders.

To have both heads remaned (NO CRACKS) you are looking at
$1100-$1400 everything included.

All new motor...I would question that one

Jim@BAWS

JKTX21
06-05-2007, 06:21 PM
JKT- who are you callin' a new head?

I was calling you The All-Knowing Head of All Things!

You're like Ken Jennings of boat mechanical operations.

:D

etduc
06-05-2007, 06:23 PM
Seriously, if you took it in for a tune-up, I have to assume it ran before that. Who did you take it to, what did you have them do, other than a tune-up and how are they explaining the fact that it no longer runs at all?

If it definitely ran before they got it, it should run when you get it back, regardless of how well.

The first thing I would do is talk to the service manager about the condition pre/post service. Don't get into a technical peeing match and if that's all he wants to do (talk over your head), ask to talk to the GM or owner. Just ask why it doesn't run at all now, don't get into the fine details. It could be as simple as the tech attaching the plug wires on a GM, in the Ford pattern. If it's a '90, I thought they all had 351 motors, except for the big block. Seeing 350 and being in "350 mode" while working on a 351 can be a problem and vice-versa.

Next, I would call around and ask how much an estimate costs, and tell them what the situation is. The main things that need to be done are:

1) Check for spark, both intensity & consistency and correct timing/firing order
2) Check for fuel quality and pressure- this should be self explanatory
3) Compression/leakdown/vacuum test- this indicates the general health of the motor because if the valves and/or rings are bad, the gauges will indicate low compression and any pressure in the cylinders will leak down rapidly. Bad gaskets can also be an issue here but they don't cost as much in labor as machining/rebuilding. If the vacuum is bad, the air/fuel charge will be less than what it should be and the fuel liquid won't atomize the way it should.

If you get an estimate (all of the above work should take less than 2 hours, even with warming the motor up), post it here. Have them itemize everything they did to decide what the motor needs.

How long have you owned this boat and what is the service history? If it hasn't been tuned up in a long time or isn't used much, it could be bad fuel, clogged fuel lines, gummed up carb, etc. If the spark is non-existent, there is always a reason. If the compression and vacuum are low, it's not the end of the world. If the motor froze, overheated or was generally abused, it could get expensive but even then, the worst case is replacing the motor, assuming all else is operational.

Boy, glad I waited to post. :rolleyes:

JimN
06-05-2007, 08:57 PM
I had to google Ken Jennings, since I rarely watch Jeopardy. Thanks but there are a lot of people who know a whole lot more about these than I do.

BriEOD
06-05-2007, 09:58 PM
I had to google Ken Jennings, since I rarely watch Jeopardy. Thanks but there are a lot of people who know a whole lot more about these than I do.
Wow, finally something Jim did not know. I bet you could give ol' Ken a run for his money on Jeopardy Jim.

SkiinJ
06-05-2007, 10:21 PM
It is only getting compression in 2 valves.

SkiinJ
06-05-2007, 10:33 PM
We have only had this boat for less than a year and was only able to take it out once at the end of last summer. The boat was winterized and then it was taken directly to the boat mechanic, a Mastercraft dealer, a month ago to get it ready for summer. All they did was tune it up and flush out the bad gas and clean the gas tank. The mechanic did not elaborate on why only 2 of the 8 valves are giving compression. The other 6 valves are only compressing from the high 50's to the low 90's whatever that means! I will get more information tomorrow when we call them. Thanks again, we need all the advise we can get!

pram
06-05-2007, 10:35 PM
It is only getting compression in 2 valves.

I don't know if I understand what it is that you mean. Are you saying that you are only getting compression in 2 of the 8 cylinders? Or that only 2 of the 16 valves are opening (compressing) when the motor turns over?

6ballsisall
06-05-2007, 10:35 PM
I really think you mean cylinders instead of valves. Your boat has 16 valves, not 8 as you referred to above.

I think I'd do a little more investigating before succombing to whats been recommended by the mechanic. Low compression can be alot of different things. If anything a new set of heads might be in order. Those certainly will be alot less than a whole new motor.

pram
06-05-2007, 10:37 PM
Ah now I see I think. Did the mechanic tell you that you only have good compression in 2 of the 8 cylinders and that in the other 6 you are ranging from 60-90 pounds?

JimN
06-05-2007, 10:54 PM
"We have only had this boat for less than a year and was only able to take it out once at the end of last summer."

How well did it run that time? If it seemed to have good power and no noticeable problems, it may have overheated and cooked the head gaskets. If there's any gasket sealant around the heads where they meet the block, I would bet that it blew out from the heat and is causing the loss of compression. If that's the only problem, while the bearings may be affected from a long run while overheating, a new upper gasket set may cure it. On the other hand, if the heads are coming off anyway, it's a good time to freshen them up and maybe have the cylinders honed.

In for a penny, in for a pound.

etduc
06-06-2007, 10:20 AM
We have only had this boat for less than a year and was only able to take it out once at the end of last summer. The boat was winterized and then it was taken directly to the boat mechanic, a Mastercraft dealer, a month ago to get it ready for summer. All they did was tune it up and flush out the bad gas and clean the gas tank. The mechanic did not elaborate on why only 2 of the 8 valves are giving compression. The other 6 valves are only compressing from the high 50's to the low 90's whatever that means! I will get more information tomorrow when we call them. Thanks again, we need all the advise we can get!

I guessing, blown gaskets.

Let's face it, your going to be spending money.

Take it to any shade tree mechanic. Have him/her pull the heads. (This will require, other things being removed, but your not pulling the engine.) Have the cyclinder walls looks at. (Any heavy scaring? Oil stains? Debris?) If walls look, ok. Have heads/valves inspected. If they are damaged, buy remanufactured heads. (Auto supply stores sell them 300-500.00 a pair, plus your heads.) Have it put back together, if everything checks out. Have you Mastercraft dealer, check the work, run the boat,etc. You wil have to pay them, for the time.

Replacing the engine, is not out of the question. 17 yrs on a boat engine is a longtime. It is faster, buying a remanufactured marine engine and have it installed, than rebuild your engine. (Here in Tx, it'll run about $3500.00 max, shade tree prices) Not knocking Mastercraft dealers, they're busy this time of year, with newer boats.

I was in a simular place to you, three years ago. (1990 TRISTAR) I just needed to replace my heads. ( My engine, has well over 2000 hrs on it, and still running strong.) So you never, know.

Storm861triple
06-06-2007, 12:13 PM
Before spending money on a head gasket replacement, perform a leak down test. If you have access to an air compressor you can do it youself (myself or others can tell you how), or take it somewhere and have a leak down test performed. This will show w/o a doubt, where the issue is, and then you'll know what needs to be done to fix it.

Like JimN was saying, if it ran fine last summer, there isn't too much that could cause it to loose compression in 6 out of 8 cylinders over the winter, other than the possibility of a severe over heating that he mentioned. Even then....6 out of 8 cylinders? I've overheated SBC V-8's so bad they've seized up...and came out of it fine and continued to run great after. I am suspicious of your mechanic. JimN asked:
*Who did you take it to,
*what did you have them do, other than a tune-up and
*how are they explaining the fact that it no longer runs at all?

How about answering those questions as those answers will tell us a lot.

88 PS190
06-06-2007, 12:44 PM
i'm confused on compression in 2 valves as well.

You have a V-8 engine, to check compression you remove the spark plug and screw in a compression tester and crank the engine over till the gauge maxes out.

This gives you the compression in the cylinder. Which is during the compression stroke of the engine when both valves in the cylinder are closed and the piston comes up it compresses the air/fuel to a certain extent.

A valve I don't know how it could have compression, as it just opens and closes.

Causes of no compression in a cylinder,

Head Gaskets will blow white smoke, and you will find water in your oil
Valves and valve seats/guide seals. burn oil and you will find exaust up in your valve cover.
Holes in Pistons - will blow blue smoke
Bad rings - will blow blue smoke
Worn cylinders. - will blow blue smoke

etduc
06-06-2007, 02:06 PM
Let's cut to the chase....

1) The guy says, he don't know much about engines.
2) Really good engine mechanics, won't be working a boat shop. They'd be working at car repair or car dealerships. (Higher pay)
3) The guy, thinks he won't be in the water, this summer.

There are alternatives for boat engine repair, besides boat shops.

I just thought of something. EBAY! Buy another 190. (Not kidding!) Sell his. :cool: