MX 6.2L MPI Horizon MIE: Rebuild Recommendations Needed

[Greg_E]

This thread is a continuation of my previous thread where I had the oil analyzed and it had antifreeze and high metal levels in the oil.
I want to have a boat I can depend on next season so I think the best course of action for me is to either purchase a new GM long block or have one built with better parts provided the cost is somewhere in the ballpark. As Scott D has mentioned in my previous thread a new 377 LB can be purchased for around $4200.

I found a good shop that has all the best equipment and builds a lot of race engines and will do the job. He said he will put a manifold with carburetor on it and run it on the engine dyno before it leaves the shop. I got all the casting numbers so all we need to do is sit down and go over the list of parts to put in the engine.

When I pull the bad engine in the spring, I plan to use that as a core, should I need to rebuild the other motor.

What I have: Block Casting 10239906. 350 CI Vortec truck Gen 1 crate motor with stroker crank making it 377 CI
Head Casting 10239906
Both have Made in Mexico on the casting if that matters.

My goal: I'm not looking to build a high HP engine. It has to run with the other engine which is 320HP. I wouldn't mind a small bump in power but I don't want to add expense needlessly. Also the shafts are only 1 1/4" stainless steel and it's a fairly heavy boat, so I don't know much they can handle.

Recommendations for the LB build ?: The shop owner said he has seasoned blocks and better GM heads that will bolt right on for a good price.
I have read that the Scat crank kit is reasonably priced and probably good enough for what I need Is that the best option for my case?
Also what cam and piston choices would be suitable for this build?
Any other upgrades I should consider? Oil pump etc.

I will also need enough parts for him to run the engine on the dyno, so I wlll need an oil pan, harmonic balancer marine water pump. Some other parts that are needed like the distributor I can pull from the old engine. Is the Mercruiser oil pan a cast pan I see it is about $600. Also is the harmonic balancer the same as stock GM truck engine?

That's it for now. I'm sure I will have many more questions.

 

[Greg_E]

Found this thread with some good info. 5.7 w/carb but should be similar.
https://forums.iboats.com/search?sea...%7D&btnSubmit=

Scott D also posted in my other thread so I will copy that here.

Originally posted by Scott Danforth View Post
if you have a way of re-programming the ECM, you can build 420hp motors easy for $4200 each using new blocks and heads. about $2300 each using your blocks and heads. without re-programming, no sense to use "better parts" as it wont mater.

requires these simple changes:
LCQ style pistons (vs the flat top 4-relief stock units)
modify the heads for higher lift cam, mild porting and bowl blending
coated bearings
different cam (using the same 1.6:1 rocker ratio, however with a better profile)
roller timing set
throttle body spacer

My Reply:
I don't have a way to reprogram the ECM. I can't say that I've seen any mention of tuning software for the Mercruiser ECM but someone must be doing it. I'm only doing the one engine for now so it would not make sense to have one 320HP and the other 420HP.

 

[Scott Danforth]

then keep it stock,

 

[Greg_E]

What would be the pros and cons of changing this back to a carburetor and what would be involved? I ask because I already know that the cool fuel module needs to be replaced because the paint inside has started peeling. With a new engine I would also want to have the injectors cleaned and tested to be sure nothing has made its way past the fuel filters. I also noticed that the intake manifold has rusted through, where one of the bolts that secures it to the block goes. I'll have to wait until I get that off to see what shape it is in. Another downside for the MPI is that this boat doesn't have the Smartcraft gauges. So when an alarm triggers you don't know what is wrong.

Also I would like to get rid of the raw water drain system to clean some of the unnecessary clutter.

 

[alldodge]

MPI to carb - intake, carb, ignition system

Once changed, need to check Air Fuel Ratio (AFR) to insure a lean condition does not exist. This will take O2 sensors or many run, stop, check plugs at various speeds and no idling.

 

[Scott Danforth]

What would be the pros and cons of changing this back to a carburetor and what would be involved? I ask because I already know that the cool fuel module needs to be replaced because the paint inside has started peeling. With a new engine I would also want to have the injectors cleaned and tested to be sure nothing has made its way past the fuel filters. I also noticed that the intake manifold has rusted through, where one of the bolts that secures it to the block goes. I'll have to wait until I get that off to see what shape it is in. Another downside for the MPI is that this boat doesn't have the Smartcraft gauges. So when an alarm triggers you don't know what is wrong.

Also I would like to get rid of the raw water drain system to clean some of the unnecessary clutter.

you should be watching the gauges...... your eyes should be sweeping the gauges once every 5 seconds. you will catch anything going south before dumbcraft can detect anything and flag a warning.

your replacement engine is just a long block
a complete Mercruiser reman 6.2 is just under $12k and that DOES NOT include a heat exchanger.

you can build a complete whipple-charged motor for under that if you build it yourself.

your choice on what you want to do. however if you have heat exchangers, how did your intake manifold rust, other than lack of maintenance. if you dont have heat exchangers, how were you getting anti freeze in your oil.

 

[Greg_E]

you should be watching the gauges...... your eyes should be sweeping the gauges once every 5 seconds. you will catch anything going south before dumbcraft can detect anything and flag a warning.

I do watch the gauges. I was under the impression that Smartcraft had greater diagnostic capabilities. I don't know. I never used it or been on a boat that had it. I can only relate to what I have in my C5. Apparently they are not similar systems.

your replacement engine is just a long block
a complete Mercruiser reman 6.2 is just under $12k and that DOES NOT include a heat exchanger.

I understand that.

you can build a complete whipple-charged motor for under that if you build it yourself.

There was a time I might have done that , but I just want to go fishing and enjoy my boat. If I didn't have to do any of this I would be just fine with it. That just isn't my situation.

your choice on what you want to do. however if you have heat exchangers, how did your intake manifold rust, other than lack of maintenance. if you dont have heat exchangers, how were you getting anti freeze in your oil.

Yes I have heat exchangers. If I had to guess I would say the manifold was poorly cast or machined. The hole for the bolt should surround the bolt. What I have looks like this. C Rust is probably from condensation. I agree there has been a lack of maintenance, but it wasn't on my watch. Two motors spent in under 900 hrs total. This one was the replacement.

So from your previous post, and considering what it will cost to repair /test/replace the failing components and the complexity of the MPI system, is converting to a carb a good option? It is simpler, parts are less expensive. and done right it can't be a huge difference in fuel consumption. Just asking, I don't know those answers.

 

[Greg_E]

MPI to carb - intake, carb, ignition system

Once changed, need to check Air Fuel Ratio (AFR) to insure a lean condition does not exist. This will take O2 sensors or many run, stop, check plugs at various speeds and no idling.

I stopped at a shop today and they said if I wanted to have a long block built rather than purchase an off the shelf 377 L.B.,
they can setup the carb when they run it on the engine dyno. He did say that If I did the swap to one engine I should do it to the other at the same time, even if I don't plan on rebuilding the other engine right away. That adds more expense and I'm not sure I want to take on the extra work. I will have enough to do come spring. I just hate spending $1200 on that POS cool fuel module, but it looks like I'll be going that way.

On the subject of new 377 L.B. or rebuilt 383 L.B. would the 383 require that the ECM be reflashed with a new tune or would it be able to adjust for the small change in displacement. No other changes that would make a big change in HP. If needed, would Mercruiser dealers do the the reflash for an otherwise stock 383 rebuild? I did find a place online that does that stuff for the Mercruiser / Motorola ECMs but who is to say they are any good at it. I don't think a mail order tune is ever a good way to go especially if you have no way check A/F ratio throughout the RPM range.

Cams: What aftermarket cams would be a good substitute for the cam that came in the Mercruser 6.2? I don't want the added expense of having the head machined for a higher lift cam.

 

[alldodge]

Going from virgin 377 to bored .030 over 383 should not need any reprogrammed of the ECM so long as the cam is the same.

If you go to higher lift cam, then you need a reprogrammed. That said, you will get a basic tune given unless its done on the dyno. Even if done on the dyno there will be difference because dyno's use dry exhaust headers

Folks that can do a 555 are Whipple, Raylar and a few others

Don't know your serial number but you talking about but what cool fuel do you have, the port side pump and cooler tube or the starboard side box?

 

[Scott Danforth]

as AD posted, not enough change between a 377 and 383 to mater

however if you build a stroker SBC with better pistons, cam, etc. and change the combustion mix, you need to reprogram.

if you need to simply go fishing, buy a new 377 SBC for 4200, pull your manifold, and blast it, weld it up, machine it and have it re-e-coated.... a new Mercruiser lower manifold is just under a grand

 

[Greg_E]

Going from virgin 377 to bored .030 over 383 should not need any reprogrammed of the ECM so long as the cam is the same.

If you go to higher lift cam, then you need a reprogrammed. That said, you will get a basic tune given unless its done on the dyno. Even if done on the dyno there will be difference because dyno's use dry exhaust headers

Folks that can do a 555 are Whipple, Raylar and a few others

Don't know your serial number but you talking about but what cool fuel do you have, the port side pump and cooler tube or the starboard side box?

Thanks for that information AD.

It is the Cool Fuel III but not the new "improved" version.

The unofficial paperwork I received with the boat said it was a 2006 MX 6.2L MPI Horizon MIE but I could not find the serial number anywhere on the engine. When I did a serial number search everything is OK when I type OW698 The next digit is invalid. Contacted Mercruiser and they .could offer no help. Tried substituting some other numbers but came up with two Black Scorpion motors. Bottom line is: I don't know what it is.

The starboard engine has theGen II log style cooler separate fuel pump and spin on filter. Both engines have them mounted on the starboard side.

 

[Greg_E]

as AD posted, not enough change between a 377 and 383 to mater

however if you build a stroker SBC with better pistons, cam, etc. and change the combustion mix, you need to reprogram.

if you need to simply go fishing, buy a new 377 SBC for 4200, pull your manifold, and blast it, weld it up, machine it and have it re-e-coated.... a new Mercruiser lower manifold is just under a grand

I looked around. I haven't been able to find one for $4200 yet. Cheapest I found was around $4600 plus around $300 for shipping and home delivery lift service. Can you point me in the right direction?

 

[alldodge]

Thanks for that information AD.

It is the Cool Fuel III but not the new "improved" version.

The unofficial paperwork I received with the boat said it was a 2006 MX 6.2L MPI Horizon MIE but I could not find the serial number anywhere on the engine. When I did a serial number search everything is OK when I type OW698 The next digit is invalid. Contacted Mercruiser and they .could offer no help. Tried substituting some other numbers but came up with two Black Scorpion motors. Bottom line is: I don't know what it is.

The starboard engine has theGen II log style cooler separate fuel pump and spin on filter. Both engines have them mounted on the starboard side.

You should either have one of these, left or right side of pic

 

[Greg_E]

Cool Fuel III on the motor I'm replacing. Peeling paint in the filter housing. Picture on the right.
The 2003 engine has the other log style cooler. See my post #11.
The image you posted looks like the new version. with the threaded fitting for the raw water intake and anodized, not painted.

 

[alldodge]

Cool Fuel III on the motor I'm replacing. Peeling paint in the filter housing.
The 2003 engine has the other log style cooler. See my post #11.
The image you posted looks like the new version. with the threaded fitting for the raw water intake and anodized, not painted.

Good luck

unsubscribe

 

[Scott Danforth]

Here you go, wait for a sale

http://centerstateengine.com/new-ma...rine-base-engine-replaces-years-1996-present/

 

[Greg_E]

Thanks for that info.

Probably a good time to replace all the cooling hoses when I assemble the motor. Not a lot of hours on them but I'm sure they have never been replaced, making them 14 years old. I looked on Mercruiser parts site hoping to find a kit with all the hoses. Everything was listed individually. Is there anybody that sells a kit?

Also, should I replace the distributor gear so the it wears in with the new motor?

 

[Scott Danforth]

there is no kit for the hoses

no need to replace the dizzy gear, you dont have enough hours on the motor to have ever gotten any wear if there was regular oil changes

 

[Scott06]

Here you go, wait for a sale

http://centerstateengine.com/new-ma...rine-base-engine-replaces-years-1996-present/

That’s a good price most similar sellers are at $5200 for same thing

 

[Scott Danforth]

That’s a good price most similar sellers are at $5200 for same thing

most subscribe to the gouge and pillage philosophy