5.7 chevy replacement engine for Mastercraft

[Bigbore500r]

OK.

He's at the mercy of the mechanic since it doesn't sound like he's capable of doing this in the driveway...

We have low compression. Low compression due to wear can't very well destroy the plugs as is being described, they'd just be dirty and fouled depending on WHY the compression is low.

If this were me, I'd perform a leakdown test on those 2 bad holes....open up the oil cap and pull the airbox to access the throttle body. With the valves closed, pressurize the cylinder and hold a piece of tissue paper over the oil fill hole...see if air is blowing out and moving your tissue paper. If not, open the throttle and hold it in front of the throttle body. If not, hold it over the exhaust dump. Air is leaking somewhere if he has 55psi of compression. If it's coming out of the oil fill, then the rings or cylinder walls are the issue. If it's coming out of the throttle body, we have a leaky intake valve. If it's coming out of the exhaust, we have a leaky exhaust valve.

If you can isolate the problem to the valves, then I'd pull the heads...if the cylinders look good, do a valve job and put it back together. If the cylinders have damage, it needs an engine (or a rebuild).

YES !

Id also ask to see the spark plugs that "have the electrode blown off" - They don't just mechanically damage sparkplugs unless some major carnage has happened. Not saying it's impossible, but ......maybe the mechanic saying "its blowing out the plugs" is his slang way of saying it's fouling plugs. And then - oil fouling? fuel fouling? Etc

 

[lbhsbz]

The plugs were actually getting blown out of their seating when the boat was running twice. Thought it was a bad plug but it happened twice in the same trip.

What does this mean? Spark plugs screw into threaded holes in the cylinder heads. Did the plugs physically leave the cylinder heads so they were dangling there hanging off the ends of the high tension leads (spark plug wires)? When attempting to reinstall, was the guy installing them able to tighten them properly or did they just spin in the holes? Also...have to ask...when the plugs were reinstalled (assuming they actually blew out)...were tools used or were they just screwed in finger tight?

 

[Bigbore500r]

This is exactly what we need. Please keep me posted. My cell is 619-517-7192 Thank you. Scott

Just an FYI - 2 things you need to check for to make sure the SBC your looking at is compatable with your curent motor

1) You have a passenger side dipstick, and one-piece rear main seal. Only matters if you are re-using your oil pan, and most likely the motor your looking at will have the same setup if its from the 80's - 2000's

2) Your cylinder heads (and intake manifold) might be vortec heads. Merc made that model motor for a long time, and the end of the production run ran a few years past the "changeover" point where GM started using the Vortec head design in vehicles. It's hard to tell from your pictures. If the intake manifold bolts to the cylinder head with the bolts straight up and down (instead of angled, 90 degrees to the cylinder head intake surface) - They are vortec heads. Theres also gonna be casting marks on front of the heads that look like sharp little triangles, if they are vortec. Again - this only matters if you are keeping your intake manifold setup. If your gonna run the setup thats on the "new to you" motor - doesn't matter.

If it was me (im a cheap ass and a gear-head) - I'd spend a little time doing the simple diagnostic tests @lbhsbz described, before ruling out the motor. Alot of mechanics are more "parts swappers" than diagnostic minded. If it just needs heads, those can be sourced cheap and slapped on there quickly. If its oil fouling plugs - motor is most likely done, but it COULD be from valve guides / seals. If its fuel fouling due to low compression, and the comnpression is low due to leaking valves - new heads cure this.
I'd get specifics from the mechanic, and if he's a good mechanic he would be speaking on these terms and be able to answer these questions.

 

[JDKRXW]

Just an FYI -

2) Your cylinder heads (and intake manifold) might be vortec heads. Merc made that model motor for a long time, and the end of the production run ran a few years past the "changeover" point where GM started using the Vortec head design in vehicles. It's hard to tell from your pictures. If the intake manifold bolts to the cylinder head with the bolts straight up and down (instead of angled, 90 degrees to the cylinder head intake surface) - They are vortec heads. Theres also gonna be casting marks on front of the heads that look like sharp little triangles, if they are vortec. Again - this only matters if you are keeping your intake manifold setup. If your gonna run the setup thats on the "new to you" motor - doesn't matter.

This.
I've got a 95 Prostar 205 with TBI and it's a 'pre' vortec.
I think this might be important because you may be forced to use your current intake/f.i. set up because there's not a lot of space between the spark arrestor and the engine cover.
That Merc Magnum looks pretty tall. Those risers will have to be checked for fit under the hump too.[/QUOTE]

 

[Lumpy]

Kinda grazed thru this thread…sounds like a blown head gasket and someone forced the wrong plugs into the holes…never heard of pugs just blowing out of a small block before let alone putting them back in again.

 

[DRYHEAT]

It would also be nice to know compression numbers on other cylinders.

 

[Cole Trickle]

From the description the mechanic gave you I think I would want a new mechanic. He just wants you to throw a new crate motor at it when it could be something much cheaper.

The blowing out spark plugs deal confuses and concerns me.

How many hours are on the engine? SBC are pretty bulletproof if left alone.

 

[Rotten deal]

This is exactly what we need. Please keep me posted. My cell is 619-517-7192 Thank you. Scott

Left you a voicemail.

 

[Tamalewagon]

What does this mean? Spark plugs screw into threaded holes in the cylinder heads. Did the plugs physically leave the cylinder heads so they were dangling there hanging off the ends of the high tension leads (spark plug wires)? When attempting to reinstall, was the guy installing them able to tighten them properly or did they just spin in the holes? Also...have to ask...when the plugs were reinstalled (assuming they actually blew out)...were tools used or were they just screwed in finger tight?

The tops of the plugs left the cylinder head with a loud bang. Happened on a trip to Parker last year. We replaced it, happened again, replaced once more and was fine for the trip. The guys at Dirty Deeds helped us out (I have high praise for this shop so I'm not calling them out at all) so the plugs were installed correctly.

 

[Tamalewagon]

Just an FYI - 2 things you need to check for to make sure the SBC your looking at is compatable with your curent motor

1) You have a passenger side dipstick, and one-piece rear main seal. Only matters if you are re-using your oil pan, and most likely the motor your looking at will have the same setup if its from the 80's - 2000's

2) Your cylinder heads (and intake manifold) might be vortec heads. Merc made that model motor for a long time, and the end of the production run ran a few years past the "changeover" point where GM started using the Vortec head design in vehicles. It's hard to tell from your pictures. If the intake manifold bolts to the cylinder head with the bolts straight up and down (instead of angled, 90 degrees to the cylinder head intake surface) - They are vortec heads. Theres also gonna be casting marks on front of the heads that look like sharp little triangles, if they are vortec. Again - this only matters if you are keeping your intake manifold setup. If your gonna run the setup thats on the "new to you" motor - doesn't matter.

If it was me (im a cheap ass and a gear-head) - I'd spend a little time doing the simple diagnostic tests @lbhsbz described, before ruling out the motor. Alot of mechanics are more "parts swappers" than diagnostic minded. If it just needs heads, those can be sourced cheap and slapped on there quickly. If its oil fouling plugs - motor is most likely done, but it COULD be from valve guides / seals. If its fuel fouling due to low compression, and the comnpression is low due to leaking valves - new heads cure this.
I'd get specifics from the mechanic, and if he's a good mechanic he would be speaking on these terms and be able to answer these questions.

Sadly I am not terribly mechanically inclined. However, the engine is an Indmar 5.7. I am not sure if the replacement engine in question will be compatible with the 1997 Prostar 205.

 

[Tamalewagon]

Left you a voicemail.

Will call you today.

 

[Tamalewagon]

From the description the mechanic gave you I think I would want a new mechanic. He just wants you to throw a new crate motor at it when it could be something much cheaper.

The blowing out spark plugs deal confuses and concerns me.

How many hours are on the engine? SBC are pretty bulletproof if left alone.

The engine has about 600 hours on it and was solely used for waterskiing at Canyon Lake in CA. Completely stock engine.

 

[Tamalewagon]

What does this mean? Spark plugs screw into threaded holes in the cylinder heads. Did the plugs physically leave the cylinder heads so they were dangling there hanging off the ends of the high tension leads (spark plug wires)? When attempting to reinstall, was the guy installing them able to tighten them properly or did they just spin in the holes? Also...have to ask...when the plugs were reinstalled (assuming they actually blew out)...were tools used or were they just screwed in finger tight?

I had my son ask the mechanic to do the leakdown tests and he said he could not do that test. He would have to tear the engine apart to do the testing. true or false?

 

[HST4ME]

lol false

 

[lbhsbz]

I had my son ask the mechanic to do the leakdown tests and he said he could not do that test. He would have to tear the engine apart to do the testing. true or false?

Pull the boat outta there, he's a fucktard.

San Diego right? Shit, bring it here, I'll do it.

 

[Tamalewagon]

Pull the boat outta there, he's a fucktard.

San Diego right? Shit, bring it here, I'll do it.

My son's boat is in Phoenix.

 

[lbhsbz]

My son's boat is in Phoenix.

Ooof...I got lucky. lol.

Pull the boat outta there anyway. I'm sure some inmates out that way can recommend someone to do an actual diagnosis.

 

[Tamalewagon]

From the description the mechanic gave you I think I would want a new mechanic. He just wants you to throw a new crate motor at it when it could be something much cheaper.

The blowing out spark plugs deal confuses and concerns me.

How many hours are on the engine? SBC are pretty bulletproof if left alone.

Yup...he wants to charge me $10K to throw a refurbished motor in the boat.

 

[Tamalewagon]

Anyone have good recommendations for a shop in PHX?

 

[Badchoices03]

I had my son ask the mechanic to do the leakdown tests and he said he could not do that test. He would have to tear the engine apart to do the testing. true or false?

Is the mechanic in Canyon Lake? If so, who is it?

*edit...nevermind I see the boat is now in Phoenix.

 

[Tamalewagon]

Is the mechanic in Canyon Lake? If so, who is it?

No the mechanic is in Phoenix. It could be a miscommunication because I have not spoken directly with them, just my son. I don't want to damage their reputation unjustly.

 

[poncho]

Anyone have good recommendations for a shop in PHX?

What Part?

 

[poncho]

Yup...he wants to charge me $10K to throw a refurbished motor in the boat.

If he is not able to perform a leak down test or unwilling I would seriously question going forward, this could easily turn into a ruined summer.
A new engine sounds like it would solve all of your problems but what if there are underlying issues and that shop isn't willing to look for those first.
As a Chief Engineer on a boat I usually know what will fix an issue but I'm more concerned with how the problem came about in the first place.

 

[Tamalewagon]

Kid is taking the boat to Laken Water Sports on the 27th. They said the test takes about a week (probably due to their schedule) so we'll know what's up with the engine around the 5th of April. Finally some positive news...

 

[Cole Trickle]

If that pull out engine shown is in good shape with decent hours for a good price that's the move if it is the same generation and fits.

I would clean it up and re gasket the easy stuff and rebuild the carb.

Perhaps one of his buddies that lives out there has a dad,uncle,etc that could help and has a hoist or forklift to swap the motors.

Labor is gonna kill him paying a shop considering the value of the boat.

 

[obnoxious001]

What the hell happened to those $2000 GM longblocks that used to be at Jegs/Summit/Everywhere?

Bidenomics. Check prices now. I recently rebuilt three "stock" type 350's for dirt track racing, got pretty pricey even with "stock" parts.

 

[poncho]

Bidenomics. Check prices now. I recently rebuilt three "stock" type 350's for dirt track racing, got pretty pricey even with "stock" parts.

I bout shit my pants the other day when I saw this price, think I'm going to lower my rev limiter this summer.

https://www.jegs.com/i/Dart/301/31223344/10002/-1

 

[rrrr]

Bidenomics. Check prices now. I recently rebuilt three "stock" type 350's for dirt track racing, got pretty pricey even with "stock" parts.

Last month I got an estimate of $2100 from the DFW high volume engine rebuilder to do the 352 FE in my '66 Ford. They have a 12/12K warranty.

I was surprised it was so reasonable.

 

[Bigbore500r]

Pull the boat outta there, he's a fucktard.

San Diego right? Shit, bring it here, I'll do it.

x2

 

[txmxer1]

Wonder where he took it, Laken was great to me. They do quality work, their mechanic is great with electrical too and got some gremlins taken care of for me.

 

[74 spectra20 v-drive]

If this is in a boat I would rebuild it, most of the reman stuff will be for smog engines or you pay a ton for a performance engine. If you have the chops to build do it! I just put a reman in my 2000 C2500, pulled the original engine out at 402,000. I bought this new so I new that this thing had never been opened up never hot etc etc... we used the old block for a project in my Son's buddies postal jeep. The engine came apart super clean not a stuck bolt nothing... the SBC is a pretty simple engine, throw a few performance parts at her and you will be good for 20 years.

 

[obnoxious001]

Last month I got an estimate of $2100 from the DFW high volume engine rebuilder to do the 352 FE in my '66 Ford. They have a 12/12K warranty.

I was surprised it was so reasonable.

I think I have a standard bore 352 block, and a crankshaft if you know anyone looking. Think they are 1964 dates.

 

[Tamalewagon]

Wonder where he took it, Laken was great to me. They do quality work, their mechanic is great with electrical too and got some gremlins taken care of for me.

He took the boat to Laken to do the leak down testing. Should be complete early April.

 

[txmxer1]

He took the boat to Laken to do the leak down testing. Should be complete early April.

Nice, yeah I felt confident in the work their mechanic did for me. Other shop in town gave up on tracing down the electrical problem after weeks of trying and their guy had it working perfect in a day.

 

[Tamalewagon]

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Thanks to Jeff, my kids boat should be back on the water in about 2 weeks. His engine was toast. We will know the complete story today but the engine swap will start tomorrow.

Thanks again Jeff.