My Mercruser has a Chevey S10 4.3L engine in it

Saline Marina

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The engines are not clearanced differently. That is a outright lie. A truck or car or boat engine can all come off the engine plant assembly line and go wide open throttle under max load for several hundred hours (its best to break it in a little first but you get the idea) with no damage.

At this point in time, the "old" ironhead 90 degree V engines aren't used in vehicles any more, aluminum heads and sometimes blocks have taken over. But there's a place for the all cast iron engines; boats, forklifts, generator and air compressors all need a simple torquey durable motor.
 
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JaCrispy

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IIRC, the fuel system guideline is all steel lines except the one from the tank to the filter.

BTW - cars that drive on the freeway are at a constant rpm/load for long periods of time. That so called...mechanic is a nutjob.
 

thumpar

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IIRC, the fuel system guideline is all steel lines except the one from the tank to the filter.

BTW - cars that drive on the freeway are at a constant rpm/load for long periods of time. That so called...mechanic is a nutjob.
A1 fuel hose is also acceptable. My system is a combination of both.
 

thumpar

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The boat is a 91. Its 13 years old. The Boat is not rotten. And the transom is solid. But I will print out all from this page and bring it to my Mechanic. I really don't know what was done to this engine. But since the manifolds were welded I suspect trouble. A long block installed was $3,000. Another $1,000 for the manifolds. And if any of the other parts are not marine I will have to purchase them. The wiring was a mess from someone who does not know how to wire. I am a retired electrical tech. I have been in Aviation mechanics, Plumbing, Air conditioning, Generators, Diesels, Building trade, and retired from a public water utility. But not in the marine field. I understand the workings, problems and theory of an internal combustion engine. And with my Aviation experience have done some overhauls. What he told me about RPM's and tolerances made some sense in the terms of engine heat and expansion. But I'm not in this field so I will talk with him about this. And I'd rather have a new engine to start with that I am maintaining from scratch. Thanks guys for all the come back. And God bless.
Why would you go back to a mechanic that is either lying to you or doesn't know what he is talking about? The RPMs and tolerances are the same for an S10 engine and a marine 4.3l. They came off the same line.. Same pistons, same rings, same bore, same crank ect.
 

Scott Danforth

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The boat is a 91. Its 13 years old. The Boat is not rotten. And the transom is solid. But I will print out all from this page and bring it to my Mechanic. I really don't know what was done to this engine. But since the manifolds were welded I suspect trouble. A long block installed was $3,000. Another $1,000 for the manifolds. And if any of the other parts are not marine I will have to purchase them. The wiring was a mess from someone who does not know how to wire. I am a retired electrical tech. I have been in Aviation mechanics, Plumbing, Air conditioning, Generators, Diesels, Building trade, and retired from a public water utility. But not in the marine field. I understand the workings, problems and theory of an internal combustion engine. And with my Aviation experience have done some overhauls. What he told me about RPM's and tolerances made some sense in the terms of engine heat and expansion. But I'm not in this field so I will talk with him about this. And I'd rather have a new engine to start with that I am maintaining from scratch. Thanks guys for all the come back. And God bless.

Your math is off. 2014-1991 is 23.

And I suggest a new mechanic

Marine motors come from the GM industrial engine division (with only a very few exceptions). other than the 3.0 which comes out of Mexico, the remaining V engines come out of the Tonawanda Engine Plant. This is the same plant that makes the GM truck engines. The ONLY difference between a marine engine and the truck engine is the marine motor gets brass core plugs, stainless MLS head gaskets, an industrial cam (same cam that is in natural gas motors and trash pump motors). The Marine motors get the Industrial engine oil pan (usually larger sump)

The motors are sold as long-block assemblies to the marinizers which include Volvo Penta, Mercruiser, PCMC, Ilmor, Indmar, and a few more. These companies bolt on exhaust and intake components that they source from a common handful of casting houses, such as Buddy Barr, Osco, etc. They then bolt on ignition systems, fuel systems, heat exchangers (from a common handful of heat exchanger vendors).

Now the exception. Brunswick, which owns Mercury, Mercruiser, and Mercury Racing, have developed within the last few years, their own castings for 4 bangers and V6 power to replace the 4.3. These were announced earlier this year. Why - because GM is phasing out the 4.3. A few years ago, Mercruiser also went away from the 8.1 liter (496) to go with the 8.2 liter (502). They took the 525 and detuned it to the 425 as GM discontinued the 8.1

Brunswick also gets blocks and heads from the GM performance parts division for many of their motors. However these motors come from the same GM engine plants.
 
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Fishermark

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I thought no rubber lines on the engine/near heat?

That's a common misconception. Marine Type A1 - and even other types - are allowable and even appropriate in some instances. In fact, the hard line doesn't even have to be steel. My old Sea Ray had copper line leading from the tank. You have to have a flexible line between the engine and where it connects to the hard line.
 

Technoid

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Sep 14, 2014
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Your math is off. 2014-1991 is 23.

And I suggest a new mechanic

Marine motors come from the GM industrial engine division (with only a very few exceptions). other than the 3.0 which comes out of Mexico, the remaining V engines come out of the Tonawanda Engine Plant. This is the same plant that makes the GM truck engines. The ONLY difference between a marine engine and the truck engine is the marine motor gets brass core plugs, stainless MLS head gaskets, an industrial cam (same cam that is in natural gas motors and trash pump motors). The Marine motors get the Industrial engine oil pan (usually larger sump)

The motors are sold as long-block assemblies to the marinizers which include Volvo Penta, Mercruiser, PCMC, Ilmor, Indmar, and a few more. These companies bolt on exhaust and intake components that they source from a common handful of casting houses, such as Buddy Barr, Osco, etc. They then bolt on ignition systems, fuel systems, heat exchangers (from a common handful of heat exchanger vendors).

Now the exception. Brunswick, which owns Mercury, Mercruiser, and Mercury Racing, have developed within the last few years, their own castings for 4 bangers and V6 power to replace the 4.3. These were announced earlier this year. Why - because GM is phasing out the 4.3. A few years ago, Mercruiser also went away from the 8.1 liter (496) to go with the 8.2 liter (502). They took the 525 and detuned it to the 425 as GM discontinued the 8.1

Brunswick also gets blocks and heads from the GM performance parts division for many of their motors. However these motors come from the same GM engine plants.

Your right, 23 yrs. To much on my mind right now. Well I had a long talk with my Mechanic. He told me to look it up. And I am still searching Mercury and Chevy for spec differences. Now this is what I was told. The Chevy 4.3 has a max sustainable RPM of 4,000. That's not max peak rpm that you would get for a short burst. And the Mercruser is rated 4800 max sustainable rpm. The truck engine is made for stop and go. If you ran a boat engine that way it would load up. Now a truck engine is not designed to run at cruise RPM like the boat. The Carb is ported different. The cam lift is smaller and the lobe degree is different. I have been told to look up the engine spec at Mercury Marine.co. And also go to Chevy Marine .com. Then look up Chevy S10 engine spec. Plus as I have stated before this engine that is in there now might have a cracked block. Or other damage. I don't want to take the chance wasting money on labor only to be told I have a blown engine. I would rather have a new engine with a warrenty and guaranty. So how many of you out there are using an S10 pick up engine in your boat??? How many hours did you get out of that truck engine with no problems?? I want to know? How many of you have put your boat engine in your truck and got 100,000 miles out of it?? This is the question my mechanic has put to you. And be honest about it.
 

thumpar

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Your mechanic is still an idiot and selling you ocean front property in Arizona. They are the same engine internally. The gurus here are experts. Take their advice.
 

H20Rat

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So how many of you out there are using an S10 pick up engine in your boat??? How many hours did you get out of that truck engine with no problems?? I want to know? How many of you have put your boat engine in your truck and got 100,000 miles out of it?? This is the question my mechanic has put to you. And be honest about it.

Don't know about a 4.3, I know lots of guys have used cheap shortblock crate 350's for v8 replacements. Complete non-marine engine, just re-use the marine heads, plugs, and accessories. Now if you know the genesis of the 4.3 v6, it is literally a 350 v6 minus about 8 inches of block, and 2 cylinders.

The other thing to consider... RV's... The load on an RV is nearly identical to a boat, if not worse. LOTS of very high load conditions, and sustained for a very long time. (well, as long as you can drive between fuel stops) Again, not many RV's with 4.3's, but LOTS with 5.7's and 7.5's, both very popular in boats. Guess what, they don't use marine engines in those...

So... Either listen to the salesm... I mean mechanic, or not.
 
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DaveG55

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On the one hand you have a mechanic who has a vested interest in convincing you to spend $4k-$5k.
On the other hand you have several people here, some mechanics in their own right, with no stake in your decision trying to help you.
In the end, its up to you who you choose to believe and how you choose to spend your money. Good luck with your decision.
 

Bondo

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Your right, 23 yrs. To much on my mind right now. Well I had a long talk with my Mechanic. He told me to look it up. And I am still searching Mercury and Chevy for spec differences. Now this is what I was told. The Chevy 4.3 has a max sustainable RPM of 4,000. That's not max peak rpm that you would get for a short burst. And the Mercruser is rated 4800 max sustainable rpm. The truck engine is made for stop and go. If you ran a boat engine that way it would load up. Now a truck engine is not designed to run at cruise RPM like the boat. The Carb is ported different. The cam lift is smaller and the lobe degree is different. I have been told to look up the engine spec at Mercury Marine.co. And also go to Chevy Marine .com. Then look up Chevy S10 engine spec. Plus as I have stated before this engine that is in there now might have a cracked block. Or other damage. I don't want to take the chance wasting money on labor only to be told I have a blown engine. I would rather have a new engine with a warrenty and guaranty. So how many of you out there are using an S10 pick up engine in your boat??? How many hours did you get out of that truck engine with no problems?? I want to know? How many of you have put your boat engine in your truck and got 100,000 miles out of it?? This is the question my mechanic has put to you. And be honest about it.

Ayuh,...... Welcome Aboard,..... The bold, underlined, is the Only Truth in that statement,......

'n, Ayuh,... The 4.3l block in My barge came from a fresh S-10 wreck, replacin' the Merc block that was Frozen, 'n Cracked,.....

That was over 15 years, 'n nearly 2,000 runnin' hours. ago,....
 
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Walt T

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Stay away from that non mechanic. He is shoveling more and more to cover for his own ignorance. These guys know of what they speak. Decades upon decades of experience here. I've built motors for 30 years and they have ALL been built the same as automotive specs. Bearing clearances, piston to wall clearances ALL the same. Seen it, built it, and BS'd no one. Well, ok I've BS'd but it's all in fun.
 

JaCrispy

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Sounds like the owner and mechanic have no clue about engines.

I would suggest buying a running boat.
 
Joined
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On the one hand you have a mechanic who has a vested interest in convincing you to spend $4k-$5k.
On the other hand you have several people here, some mechanics in their own right, with no stake in your decision trying to help you.
In the end, its up to you who you choose to believe and how you choose to spend your money. Good luck with your decision.

This is pretty much the bottom line... No one here will gain anything no matter what you decide.. I tend to rather believe people that won't make any money on me.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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Your right, 23 yrs. To much on my mind right now. Well I had a long talk with my Mechanic. He told me to look it up. And I am still searching Mercury and Chevy for spec differences. Now this is what I was told. The Chevy 4.3 has a max sustainable RPM of 4,000. That's not max peak rpm that you would get for a short burst. And the Mercruser is rated 4800 max sustainable rpm. The truck engine is made for stop and go. If you ran a boat engine that way it would load up. Now a truck engine is not designed to run at cruise RPM like the boat. The Carb is ported different. The cam lift is smaller and the lobe degree is different. I have been told to look up the engine spec at Mercury Marine.co. And also go to Chevy Marine .com. Then look up Chevy S10 engine spec. Plus as I have stated before this engine that is in there now might have a cracked block. Or other damage. I don't want to take the chance wasting money on labor only to be told I have a blown engine. I would rather have a new engine with a warrenty and guaranty. So how many of you out there are using an S10 pick up engine in your boat??? How many hours did you get out of that truck engine with no problems?? I want to know? How many of you have put your boat engine in your truck and got 100,000 miles out of it?? This is the question my mechanic has put to you. And be honest about it.

your mechanic is still an idiot

and yes, the carb is ported different, the cam is different between marine and truck. it is also different between natural gas motor and auto. however the part numbers for the block, heads, crank, con rods and pistons is all the same. The flywheel for a boat is the same as the flywheel for a genset - it is the gm manual transmission flywheel also found in the GM vehicles running a manual trans. for various installations, the intake is also the same. All of them have a reciprocating assembly balanced to run up to 5500 RPM.

I will be honest. I do know many of the engineers at Volvo Penta, GM, Ilmor, Indmar, PCMC, Mercruiser, Mercury Racing, Cummins, John Deer, Caterpillar, and Seven Marine I know the former Chief Engineer at GM powertrain and Ford powertrain. For small engines, I know the engineers at Generac, Kohler, Honda, Robbins (Suzuki), LCT, Kawasaki and Kubota. All contacts I made between designing natural gas generators, industrial power units, marine heat exchangers, and outdoor power equipment. I still say your mechanic is an idiot and feeding you a line of bull crap.

you have a choice, believe everyone here tellin you to find a different mechanic, or believe the guy trying to sell you a $4500 bill of goods.
 

Watermann

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I would rather have a new warrantied engine than an unknown, possibly worn out cracked motor or either type that is if coin wasn't an issue. Although if it were me, being a cheapskate and all, I would find a rotten donor boat with a good low hour MC 4.3L and swap it over. Then you have no worries about marine this or auto that.

Some marine mechanics are funny that way, as far as saying what is best for your boat goes. I know one who won't even recommend using a different brand of prop on a mercruiser. :lol:
 

Silvertip

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Sep 22, 2003
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To determine who is telling the truth, ask the "mechanic" to provide his source for the specs for the marine engine. Actually have him show you the numbers. Then go to any of the web sites that post the same data for the S-10 4.3. Heck, you can even go to the library and look at the dozens of auto shop manuals. Then and only then will you know how well versed your "mechanic is". Keep in mind that production specs may change very slightly from year to year so know what you are looking at and are comparing apples to apples. If your "mechanic" says he doesn't have time, or comes up with an excuse that he can't do it right now, I think you would have your answer.
 

duped

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New block or not, there are still 100s of other things that are more likely to strand you. It's the reality of boats, old and new. Do a search on here for how often someone is stranded by a total engine failure that you are worried about. Not that common compared to drive failure, electronic gremlins and every other thing.
 

Walt T

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I've had fuel pumps, water pumps, electrical failures, shift cables, spun hubs, damaged props, drunken friends, blower explosions, all leave me stranded on the water but I have never had a total engine or drive failure. Volvo, Merc, GM, Ford, Bravo, OMC, Chryslers, Casale, Borg Warner, all of the big main components are designed to keep working. They almost ALWAYS fail due to lack of maintenance or damage caused by operator error. There's no shortage of owners here who will disagree and tell me stories of drives and motors that filled up with water and suffered catastrophic damage all by them selves. If a drive gets water in it it's nearly always because a seal or bellows was damaged and then the owner did not check the oil all season. That is not a drive failure, that is a maintenance error. Owners will also disagree with me by saying the shift stuff inside just broke. We all know shifting problems make themselves apparent and give you time to fix it before it lets go. The second I see water in my drives they are done. It's reseal time. Sure I've heard a few stories of blown drives only a few hours old, but I haven't seen them personally. I've had customers break shafts in drives because they didn't believe me when I told them the new engine they have can easily break it and then expect me to buy them a drive. This is why I no longer build for people outside my trusted base.
A friend just bought a really nice Sea Ray 240 Weekender with a supposedly new 350 in it and the salesman said it was a rebuilt drive. Turns out it was a saltwater boat, the upper gears in the drive had rust and pits in the bearing and race, the engine was probably replaced but the manifolds and risers were not new.
if his engine locks up and bends rods it's not gonna be the engines fault. If that drive top gear shreds it's a maintenance failure. The guys are exactly right. Whatever you get, take very good preventive care and you'll most likely get stranded by the myriad of other systems on the boat.
That's the problem with being a mechanic. We know all too well about flying machines in pieces on the ground and boats in pieces on the bottom of the lake. Checking the drive oil by loosening the drain plug and letting a few drops out after every boating day can save you grief. Loosening the bellows clamp and checking for water every time can save a large unexpected expense such as a divorce lawyer. Following a strict replacement regimen for exhaust manifolds and risers goes without saying, especially in sea water. Too many folks get a sense of security because they boat in freshwater and forget that the manifolds and risers are built by humans and assembled in the boat by humans using a very thin flimsy riser gasket. Boat transom assemblies, Gel coat, engines, drives, are all assembled by hand in the hulls and the potential for mistakes is astronomical compared to mass produced automobiles. For the huge expenses involved in owning and maintaining a boat there are way to many failures. From the factory to the dealer to the owner, all are touched by hands that are controlled by varying levels of intelligence and experience. Then add in the repair mechanic who's hands then touch it after something goes wrong and you can see how it is so confusing for a non mechanic owner who simply wants to go boating. Each and every human in that chain has his or her own opinion and point of view and it is a truly sad state of affairs for the marine service industry. Then add on all the invisible folks inside your computer telling you different things and it's very easy to see how our original poster simply cannot decide who to believe. For us mechanics it's pretty clear, but to the owners of a car, boat, plane, computer, it's like pulling teeth to get consistent answers.
Wanna hear failure stories? My biggest was a blower explosion which actually did very little damage to the engine but severely damaged my shorts. I think I can say the most failure prone component of the boat is the trailer.
 
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