Mercruiser 5.0l 4bbl conversion questions

[rgrove]

Hi all! Im a new guy, first time posting. Ive spent a bunch of time searching these forums in hopes of finding answers to my questions, but I cant seem to find them, so i figured Id post to see if someone here can kindly help.

Im looking to convert my 2bbl Mercruiser v-8 to a 4bbl, and I have a few questions, and am trying to find a part number too. Here goes:

Boat is a 2000 Rinker captiva 232
Mercruiser 5.0L I/O, w/ 2bbl carb
Vortec heads.

I am installing:

edelbrock 1409 600 cfm carb
Edelbrock Performer EPS intake

Questions are as follows:

Does anyone have a part number for the linkage bracket at the carb base? I cant find anything suitable in online parts houses, etc. Not sure what to ask local shop for (i.e. year, etc)?

Currently have a PCV hose running from port (Im assuming its referenced as sitting facing forward?) valve cover into base of 2bbl carb. However, the eddy 1409 doesnt have a pcv provision. Do I need a carb spacer with a PCV port? Or where do i run this to?

On the starboard side, about 1/3 of the way back on the current manifold is a brass flex tube that connects to the starboard exhaust riser. Is this an egr? If so, to where does it get routed on the new manifold? I thought I read somewhere in a post here that the riser just gets plugged and this tube is not reused? Is that correct?

Is there a merc part number for a fuel line that will bolt up to this? ( a longshot, I know, but I know merc has used weber carbs in the past, but not sure if with elec pump?)

What are the odds that the carb jetting will be close-to-good-enough out of the box?

I know I have to ground out the ign module (T-Bolt 5) to get base timing set - any other tricks or "gotchas"?

Please let me know if I left out any key info. I would GREATLY appreciate any and all responses - I have a lot of experience restoring/rebuilding cars, and a lot of experience boating, but not much experience rebuilding boats!

Thanks!

Ron

 

[Lyle29464]

Re: Mercruiser 5.0l 4bbl conversion questions

Sounds like you might have an auto engine. Marine engines do not use PVC valves and your new carb will not need a place to hook one. your vents from the valve covers run to the outside of the flame arrestor. If you ordered a marine carb the jetting should be ok but I would check the plugs after your first few trips to make sure it is not lean. You can get the braket for your cable from a marine salvage place or ebay. If your in saltwater you may have problems with the new manifold. I would take a close look at the alternator and starter to make sure they are not from an auto engine.

 

[John_S]

Re: Mercruiser 5.0l 4bbl conversion questions

Hi all! Im a new guy, first time posting. Ive spent a bunch of time searching these forums in hopes of finding answers to my questions, but I cant seem to find them, so i figured Id post to see if someone here can kindly help.

Im looking to convert my 2bbl Mercruiser v-8 to a 4bbl, and I have a few questions, and am trying to find a part number too. Here goes:

Boat is a 2000 Rinker captiva 232
Mercruiser 5.0L I/O, w/ 2bbl carb
Vortec heads.

I am installing:

edelbrock 1409 600 cfm carb
Edelbrock Performer EPS intake

Questions are as follows:

Does anyone have a part number for the linkage bracket at the carb base? I cant find anything suitable in online parts houses, etc. Not sure what to ask local shop for (i.e. year, etc)?

Mercruiser 805359T BRACKET worked for my '97 5.7. I don't know if there are changes in throttle for 2000.

Currently have a PCV hose running from port (Im assuming its referenced as sitting facing forward?) valve cover into base of 2bbl carb. However, the eddy 1409 doesnt have a pcv provision. Do I need a carb spacer with a PCV port? Or where do i run this to?

It sounds like you have a "real" pvc. Spacer or port on intake befind carb.

On the starboard side, about 1/3 of the way back on the current manifold is a brass flex tube that connects to the starboard exhaust riser. Is this an egr? If so, to where does it get routed on the new manifold? I thought I read somewhere in a post here that the riser just gets plugged and this tube is not reused? Is that correct?

This is used to heat the intake during engine warm up. There is no provision on the edelbrock, and it is aluminum and will warm up from oil splash on underside.

Is there a merc part number for a fuel line that will bolt up to this? ( a longshot, I know, but I know merc has used weber carbs in the past, but not sure if with elec pump?)

They used weber carbs but back when they still used mech fuel pumps. Look at marine flex fuel ine. iBoats has some.

What are the odds that the carb jetting will be close-to-good-enough out of the box?

Odds are good, but there is a chance of some tuning.

I know I have to ground out the ign module (T-Bolt 5) to get base timing set - any other tricks or "gotchas"?

While in base do idle mixture and idle speed as well. Elec choke may need rewiring if you use it.

Please let me know if I left out any key info. I would GREATLY appreciate any and all responses - I have a lot of experience restoring/rebuilding cars, and a lot of experience boating, but not much experience rebuilding boats!

Need a new flame arrester.

 

[xltier]

Re: Mercruiser 5.0l 4bbl conversion questions

look into a marine carb on ebay.you will be way ahead of the game.i just got one for the same swap on a 5.7.everything just hooks up.hth

 

[rgrove]

Re: Mercruiser 5.0l 4bbl conversion questions

Sounds like you might have an auto engine. Marine engines do not use PVC valves and your new carb will not need a place to hook one. your vents from the valve covers run to the outside of the flame arrestor.

It is a marine engine; its the original mercruiser lump. I was surprised too to see a PCV, but even my service manual shows it is correct. not sure if its only a couple year thing or what....

 

[rgrove]

Re: Mercruiser 5.0l 4bbl conversion questions

look into a marine carb on ebay.you will be way ahead of the game.i just got one for the same swap on a 5.7.everything just hooks up.hth

The 1409 is a marine carb; I just picked up one brand new, so Im set on that front. Id never take the chance of using an automotive carb, althought the temptation is there because I just pulled an edelbrock 500 off of our old Ford!

What year is your 5.7? If its around a 2000, can you please confirm the P/N of your throttle bracket?

 

[rgrove]

Re: Mercruiser 5.0l 4bbl conversion questions

Mercruiser 805359T BRACKET worked for my '97 5.7. I don't know if there are changes in throttle for 2000.




It sounds like you have a "real" pvc. Spacer or port on intake befind carb.



This is used to heat the intake during engine warm up. There is no provision on the edelbrock, and it is aluminum and will warm up from oil splash on underside.




They used weber carbs but back when they still used mech fuel pumps. Look at marine flex fuel ine. iBoats has some.





Odds are good, but there is a chance of some tuning.




While in base do idle mixture and idle speed as well. Elec choke may need rewiring if you use it.




Need a new flame arrester.

THANK YOU TO ALL FOR REPLYING!! I really appreciate it! And thanks John for the detailed answers. Thats exactly what I was hoping to find!

So it seems:

I can remove & plug the preheat tube from the exh riser to the manifold
I can plumb the PCV into an elbow on the top of the intake manifold (there is an open port on top of one of the runners behind the carb.) Im assuming that I cant run it into one of the flame arrestor connections, as there would be insufficient vacuum?
I have a new flame arrestor on order, specific to the edelbrock
On fuel line, if I dont end up bending/double flaring, I know i need to use A1 USCG rated.

A few other questions:

Will I need anything special to actually connect the carb linkage to the cable? i.e. a special pin, connector, stud, etc? Im asking because Im not near the boat, and want to try to get all the parts pulled together before I go out there.

Also, how on earth do you get to the timing marks? The snout of our engine is about even with the seat back, and with the t-stat housing, etc, i cant find a way to see the timing marks. (im also not that familiar with chevys, so not sure im looking on the proper side....Im assuming its on the starboard side?) Any tricks to this? Im pretty sure I can R&R the distributor and get it lined up again, but id feel better if i was able to check the timing to confirm once done.

Guys, THANkS AGAIN for all of your replies! I truly appreciate them all!

 

[John_S]

Re: Mercruiser 5.0l 4bbl conversion questions

A few other questions:

Will I need anything special to actually connect the carb linkage to the cable? i.e. a special pin, connector, stud, etc? Im asking because Im not near the boat, and want to try to get all the parts pulled together before I go out there.

I looked at your model on MercruiserParts.com and it looks like mine. Shouldn't be anything else you need. The carb stud will come off your 2brl and bracket stud off your 2brl bracket. You will have to adjust the throttle for the new carb. The fitting that goes over the bracket stud is just rotated on the treaded throttle cable.

Also, how on earth do you get to the timing marks? The snout of our engine is about even with the seat back, and with the t-stat housing, etc, i cant find a way to see the timing marks. (im also not that familiar with chevys, so not sure im looking on the proper side....Im assuming its on the starboard side?) Any tricks to this? Im pretty sure I can R&R the distributor and get it lined up again, but id feel better if i was able to check the timing to confirm once done.

That is a boat specific thing. I can see mine with the engine hatch removed, but usually remove the whole dog house because it makes it easier and is done with other maintenance items.

The timing marks are on the harmonic balancer and the referance mark is in the composite timing cover toward the port side. Hopefully you can see enough to shine the timing light through. I would never rely on just being close. Put some white paint on the 10 degree BTDC line so it shows up well.

Other:

-Review anything else that is mounted to your current intake and make sure you have a place or way to mount with the new. Reset relay, gannon, plug, etc

-Zinc chromate prime and paint the intake before installing.

-Use the special merc gasket for thermostat that has the ground connection for the sensors.

Are you using the GM vortec intake gaskets?

 

[rgrove]

Re: Mercruiser 5.0l 4bbl conversion questions

THANKS Again!!

Glad to hear there is no special connector, etc.
As for priming, I bought a can of zinc chromate primer, but it was plugged; store was closed, and I was impatient, so I used a self etching auto primer and painted it with Mercruiser phantom black; hopefully that wont mess anything up long term. I bought the primer from the local west marine, and they are niether helpful or friendly, so I wasnt anxious to try to exchange/return the primer....

I have a Merc t-stat kit on order as well. Should have the gaskets and a new t-stat, since I figured it would make sense to change it out now since its all got to come apart.

As for the intake gaskets, I ordered a set with the intake from Jegs for the vortec heads, but it appears they sent me the wrong ones. Ill probably pick up a set from local mercruiser shop and send those back....or I guess i could go to a local chevy dealer and get a set of gaskets, probably cheaper than mercruiser?

Only thing left now (I think) is to try to track down the correct throttle bracket. Im going to look on line to see if the P/N you listed looks like it will work. Id rather not have to rig something up or use a universal bracket....

THANKS again for all of your help!

 

[John_S]

Re: Mercruiser 5.0l 4bbl conversion questions

I got my bracket on ebay, but any Mercruiser dealer should be able to get it within a week. It about $40 though.

The gaskets are expensive. In the $30-40 range if I remember correctly. The ends use a special rtv, and special torque sequence.

 

[rgrove]

Re: Mercruiser 5.0l 4bbl conversion questions

I got my bracket on ebay, but any Mercruiser dealer should be able to get it within a week. It about $40 though.

The gaskets are expensive. In the $30-40 range if I remember correctly. The ends use a special rtv, and special torque sequence.

John,
Thanks again for the reply. two on-line parts houses recommended the P/N for the bracket you suggessted. Local merc dealer should have it tomorrow, around $30. I alos had them get an intake gasket set....she quoted me around $15, and said it was for the full set, so we will see if thats what I get....If not, then i suppose the local chevy dealer should have a set of gaskets to use.

Thanks again - hopefully this can help others who seek to do this change.

 

[John_S]

Re: Mercruiser 5.0l 4bbl conversion questions

The intake gaskets have a hard plastic frame and round rubber (hollow) seals around ports. Should be what was installed on yours. They are supposidly reusable, but would go with the new.


http://www.boatfix.com/merc/Bullet/97/97_01.pdf

 

[Bondo]

Re: Mercruiser 5.0l 4bbl conversion questions

If not, then i suppose the local chevy dealer should have a set of gaskets to use.

Ayuh,.... I buy Fel-pros through my local Napa...

 

[rgrove]

Re: Mercruiser 5.0l 4bbl conversion questions

WOW! You guys are really helpful! THANKS!
One other question - opinions on carb spacers? Im thinking about using a 5/8" or 1" 4 hole spacer. Ive read that this would likely increase carb signal for better part-throttle performance, and it would also let me plug in the PCV at the base of the carb rather than into one of the manifold runners (as currently ported) and risk lean-burn in one cylinder. I just dont want to sacrifice low end torque...thoughts?

 

[Bondo]

Re: Mercruiser 5.0l 4bbl conversion questions

One other question - opinions on carb spacers?

Ayuh,.... Have you even got the space in the motorbox for another inch in height,..??

 

[John_S]

Re: Mercruiser 5.0l 4bbl conversion questions

As Bondo says, make sure it fits under the hood. With a new midrise intake and new flame arrester, you might be running out of room.

A Volvo 5.0L owner did a 4bl upgrade, similiar to yours, but reported the spacer provided the additional performance. BTW, his 2brl also had a 1" spacer.

Also, outside of some minor emmisions issues, you could probably just run like prior Mercruisers without pcv, and just vents to flame arrester.

I installed a 4 hole 1" spacer on my 5.7L last weekend. Due to lake traffic, could not test wot performance. For the boating I did, couldn't detect a change good or bad. Most of that was putting around the lake with gradual accelerations, 25-45 mph cruising, and a few bursts to 50+ mph.

 

[rgrove]

Re: Mercruiser 5.0l 4bbl conversion questions

As Bondo says, make sure it fits under the hood. With a new midrise intake and new flame arrester, you might be running out of room.

A Volvo 5.0L owner did a 4bl upgrade, similiar to yours, but reported the spacer provided the additional performance. BTW, his 2brl also had a 1" spacer.

Also, outside of some minor emmisions issues, you could probably just run like prior Mercruisers without pcv, and just vents to flame arrester.

I installed a 4 hole 1" spacer on my 5.7L last weekend. Due to lake traffic, could not test wot performance. For the boating I did, couldn't detect a change good or bad. Most of that was putting around the lake with gradual accelerations, 25-45 mph cruising, and a few bursts to 50+ mph.

Thanks again! Yup, plenty of room under the hatch...I could probably fit a blower under there if i wanted to....hmmmm....

I pinged Jegs tech line, and they concurred that a 4 hole spacer would probably help bottom end just a bit. Ill probably try it with that first and see how it works.
Thanks again!!

 

[rgrove]

Re: Mercruiser 5.0l 4bbl conversion questions

Ayuh,.... I buy Fel-pros through my local Napa...

Well, I guess its off to Napa.... Merc dealer ordered the wrong gaskets, and i dont think she can get the right ones by this weekend......
Is there any difference between the fel-pro/napa gaskets and the merc? Diffferent material, etc?

Heres to hoping napa can figure out the right one....

thanks!

 

[fishaman]

Re: Mercruiser 5.0l 4bbl conversion questions

I have just completed exactly the same conversion, but on a 5.7 engine. The original Merc setup was 2bbl carb, PCV, heating tube, and cast iron manifold.
It was changed to Edelbrock Vortec Performer intake and Weber 4bbl electric choke carb which is a carbon copy of Edelbrock 1409.

Intake gasket - I used the MS98000T Felpro Vortec Intake Gasket set. Heared too many storied about leaking Vortec intakes, so used the most advanced one from Felpro. It is manufactured from heavy gauge aluminum with plastic overlays, and looks like it will outlive the engine. Unfortunately, it comes only in a kit with a lot of stuff I do not need, and costs about $60. No leaks so far.

PCV - Just used the setup from previous years Merc 4bbl, two plastic pipes go to the flame arrester from the valve covers. Got the pipes and arrester together with the carb on EBay.

Heating tube - plugged the hole in the manifold, aluminum intake gets uniformly hot much better than a cast iron one.

Throttle bracket - I used the Merc 4bbl steel bracket, it has holes for both spread bore and square bore carbs. Came with the carburator. However, the previous 2bbl bracket also hosted a starter solenoid and Mercathode, so I had to fabricate a small platform from 1/4" aluminum attached with the same bolts as throttle bracket. Works and looks great.

Fuel line - I used a A1-15 marine fuel hose with brass barb connectors, worked very well, strategically placed the holding clamps to exclude any contact with hot parts. I believe the fuel is delivered less heated now because the hose provides better insulation, potentially more horsepower.

Very important: if you ever plan to boat in salt water, install a fresh water cooling (FWC) system. With raw water cooling, the saltwater will dissolve the aluminum in a short time. I have FWC, so there was some additional design work on connecting the termostat bypass port to the water pump.

All works great so far, I am at about 20 hours on completely rebuilt block, already feel significantly more power than with the old setup. Will soon test the WOT RPMs, probably will need a new prop with more aggressive pitch.