Mercruiser 320 EFIs
 

I recently bought a 1974 Magnum 27 sport that has been re-powered with Mercruiser 320 EFIs and Bravo 1s.

They were aparently a Mercury Hi-performance divison creation. The RPM range on the flame arresters says 5000-5400.

Any of you guys have these engines and what can you tell me about them?

Thanks,
Aaron

Re: Mercruiser 320 EFIs
 

It sounds like they are the 6.2L small blocks. 5400 sound high for stock "black" motors.

Re: Mercruiser 320 EFIs
 

Sorry....forgot to mention. They are 350/5.7L made in 1989.

Aaron

Re: Mercruiser 320 EFIs
 

320 EFI's were built in 1988-1989 model years,pretty cool motors,strong runners,but had lots of early electronic glitches. The few we bought drove us crazy. But if these are still going after 15 years you should be fine. Parts are still available but some of the efi parts are expensive. Enjoy the engines,they were pretty special back then.

Re: Mercruiser 320 EFIs
 

What are my options if the EFI becomes too hard to get parts for.....?.....can I update ECUs ?

Thanks much,
Aaron

Re: Mercruiser 320 EFIs
 

post pictures

Re: Mercruiser 320 EFIs
 

Here are a few......

Re: Mercruiser 320 EFIs
 

Sweet

Re: Mercruiser 320 EFIs
 

This was before Merc Racing started using blue paint. You've got a real nice setup there. Any history on the boat?

Re: Mercruiser 320 EFIs
 

Like Robert said, when they ran they ran very well. If the boat was used in salt, be very afraid of the intakes. NLA, if they leak, they will need to be replaced with a different setup..

Sharp boat BTW!!!

Re: Mercruiser 320 EFIs
 

I don't have much history.......I'd give my left nut to know all the history on the boat. It was in Stockton, California then Huntington Beach, Ca for a few years. Otherwise nothing.

Re: Mercruiser 320 EFIs
 

that thing looks bad azz, is it for sale????

Re: Mercruiser 320 EFIs
 

Thanks.....no it's not for sale........it's my dream boat since I was 15.....:)

Aaron

Re: Mercruiser 320 EFIs
 

My 87 Donzi Minx came from the factory with the 320 Efi. The engine had failed because electrolosis had eaten a hole in the aluminum intake, and trashed the engine. It had been sitting about a year when I bought the boat, along with the real "basket case" engine. I had all the original parts, and was going to put it back to original, but I decided to change to a carb. I read later that there is a design flaw in the injection, that shoot the fuel directly on the rings, washing the oil off the cylinder walls, and causing failure. Theres a guy here on Oso called 30 Sonic SS, or something like that, that has been battling getting two of them running for a couple of years. I sent him all the injection parts I had, along with the Ecu. Last I heard, I think he gave up and bought two new carb motors. The 320 Efi is the same longblock as the 350/300 Tempest engine. Good block, four bolt mains, forged rods and pistons. If it's running good, you might want to consider swapping to a carb now before you have trouble.

Re: Mercruiser 320 EFIs
 

Here's what it looked like before I had it.

Re: Mercruiser 320 EFIs
 

Cuda......yer bummin' me out.

The engines have a Mercathode set up on them......do you think that would help fight corrosion?

Thanks,
Aaron

Re: Mercruiser 320 EFIs
 

I don't think so, but even if it did protect it, there is still the design flaw I read about. Do a search on 320 Efi, and you'll pobably find Sonic30SS's saga with them.

Btw, it was Scott B's buddy who owned the boat before me, and he saw the holes in the intake before they were repaired.

Re: Mercruiser 320 EFIs
 

cuda's comments are bugging me out as well. I just recently purchased a 1987 Checkmate with the same 5.7 320 HP EFI motor in it. So far it runs like a champ. It was freshened in 1995 with forged pistons, Dart heads, Crane hyd roller cam, and some other misc goodies and then dyno'd with the stock EFI stuff (may have used larger injectors and or more fuel pressure) and it made 424 HP and 445 TQ. From what I have seen, none of the fuel injection, or electronics parts are available anymore, so if we were to have problems, we would either have to find used parts or make something else work. If I ever loose the EFI, I would think about going to a TPIS (Tuned Port Injection Specialties) Mini Ram set up... it looks very similar in design and then use some sort of aftermarket EFI controller. By the way, I thought these motors were only produced in 1987 and 1988 models... perhaps you have a 1988 model that was purchased in 1989???

Re: Mercruiser 320 EFIs
 

The parts listings I have found list an '87 version and '88-'89 as another set of serial #s.

The motors run perfectly......I guess I'll just maintain them and hope for the best.

Re: Mercruiser 320 EFIs
 

Classic Magnum 24Degrees! I'd never heard of those engines before :cool: Thanks for the edjamacation guys :D :drink: Hope they keep runnin' for ya till we run out of fossil fuels :evilb:

BTW, where are you showing that piece off??? I'd like to see it in person someday. Hopefully close to NJ somewhere....

Re: Mercruiser 320 EFIs
 

Cuda's Minx was a yachet tender in it's previous life.. Low hours, but may not have been maintained well as far as flushing goes.

Engine ran strong before the meltdown, I would bet they would run real well in your boat. I'm not familiar with the injection issues Cuda mentioned, but it seems to me if they are overfueling it would be fixable with some injector tweaking..??

Re: Mercruiser 320 EFIs
 

24*- nice set up, If they are running well let em' rip. I had one that ran awsome 5500 rpm all day long, and one that would lean out and blow up :( when pushed hard. I loved the look and the fuel efficiency of them and I may even go back to them with a modern ECU (true MPI) not batch fire like they are stock. The injection parts are not a Mercury specific item. heres a little secret....injectors are from Porsche 928. I have a guy here in CT that ran all the part #'s and can get anything you need. The TPS is no longer available so we are working on some sort of spacer/adaptor to mount on the end of the throttle shaft. Let me know if I can help you out, I have a bunch of info I've collected over the past 5 years.

Re: Mercruiser 320 EFIs
 

I forgot to thank Cuda for hooking me up with those parts. I've also been thinking about the supposed design flaw washing the rings, I'm thinking the batch fire may have had something to do with this, since the injectors fire when the valves are closed. I'm thinking the fuel would drop out of suspention and puddle at the valve ?

Re: Mercruiser 320 EFIs
 

Thanks guys.....

Batch fire......? I've never heard that term. Funny about those injectors. I own and operate a Porsche repair shop in Minneapolis and I noticed that the fuel pumps in the boat are the same as in my '78 911......:)

Now I just need to get educated on Chevy/Mercruiser stuff. Is it true these are 4 bolt main blocks?

I was thinking I could update to the MPI set up some day.....sounds like big money?.....might be worth it though.

Sonic......when you say running hard what does that mean? How long can I run this wide open?......It does seem to turn 5500 rpm also.

BTW: I'm running it on Lake Minnetonka just outside of Minneapolis, Minnesota.

Thanks,
Aaron

Re: Mercruiser 320 EFIs
 

I was also thinking maybe the problems were with the 1987 models?.........so maybe my 1989 versions are "sorted".

Re: Mercruiser 320 EFIs
 

Yes, the definetely are four bolt. I rebuilt that block.

Re: Mercruiser 320 EFIs
 

Possibly corrected.All the ones we sold were 87 models.And all were 4 bolt mains.

Re: Mercruiser 320 EFIs
 

I had sold a couple of Checkmates back in the day, that had these motors w/Alpha SS drives. They ran real well....however, even at the time(early '90's), they had a reputation for electrical gremlins in the computer, and oil consumption. I remember that they were an adaptation of the short-lived Crossfire injection that was used on some Vettes around the same time. I recall a particular 21 Checkmate that would run 70+mph w/the 320/Apha SS pkg. if you had the stones to hold on.
Hugh

Re: Mercruiser 320 EFIs
 

Wow I've been admiring your boat and now I see you are right here in MN. FORGET tonka and get that boat on the river. Either the Croix or the Mississippi.

Re: Mercruiser 320 EFIs
 

A few points of interest.

First, the throttle body/ plemum are around, I know where 2 are. The injectors, regulator and the like are bosch off the shelf parts.
The ECU can be replicated by Repair in Fla.

As for the engines, they run very very well, they only have issues when people that fool with them have no idea what they are playing with.
This is the same induction system that is on the merc Hi-per outbaord motors, the 2.4 and 2.5 series.
When it was mentioned that the injectors are fired in batched pairs what is ment is that two injectors are fired at the same time. This is not an uncommon thing with EFI. The best systems run sequential fuel injection, each injector fires on it's own.
I know of a lot of 320 EFI's that still are around and still run very strong. Hell the alpha SS drive that it came with it VERY saught after.
Setup Setup Setup, and they work great once correct.

RT

Re: Mercruiser 320 EFIs
 

24*- My engines were rebuilt by a builder that builds Busch series small blocks, the only deviation from stock was the balancing and the roller rocker arms. I would pin the throttles for 15 min (lifting for waves of course) at a time with no trouble at all. Of course I put in new oil coolers, new impellers, new t-stats, water pumps...ect pretty much everything brand new including injectors,fuel pumps,and regulators. As far as the blocks go yes they are 4 bolt mains and should be hydraulic roller cam, mine have World products SR heads on them I don't know if they are stock or someone replaced them.
MPI- I have been looking at the F.A.S.T. system it seems like a great set up, very user friendly and with the addition of the wide band O2 sensorit can almost tune itself.

Firewalker- Yes the injectors, fuel pumps, and regulators are Bosch off the shelf items. But thats where it ends from what I've been able to find out the TPS, IAC,Blocking rectifiers,and air temp sensors are Merc specific. This system fires four injectors at once(1-7-4-6 and 2-8-3-5). I tried to replicate exactly what Merc Hi performance put in from the factory with no changes, I did not have very good luck and I set my two aside for now. I did not want to miss anymore of our all too short boating season. I wish I r could find at a reasonable price, the Merc tester (P/N 91-16850 not the aluminum cased model though) for these systems, it would make troubleshooting much easier. After changing to carbed motors I discovered one of my tachs was bad, when I tried to time the new motor. Since you don't need to look at the tach to time the EFI, only ground the red/yellow wire. I did not know the tach was acting up at low rpms. I belive this may have had something to do with the problems I encountered with the port motor.
All in all they do run great when the are set up correctly, and I would like to rebuild and have a go at them again next year.
PS who is Repair in Florida? I could not get anyone to look at these ECUs. Even a company that advertised them on thier web site.
Joe

Re: Mercruiser 320 EFIs
 

www.rapair.com

you will need to talk to Shawn.
If anyone can do it he can.

RT

Re: Mercruiser 320 EFIs
 

Yea thats the place- CDI I've spoken with them... no interest in the 320 EFI ECU even though it was listed in their catalog. Shawn was not very helpful... no flame just the facts.
I got the impression he felt it was obsolete and not worth the effort and $$.

Re: Mercruiser 320 EFIs
 

he can be a bit crankey
I think that with enough pressure he would do it.

Re: Mercruiser 320 EFIs
 

i owned a sonic 30ss with twin 320 efi's. ran in sw on cape cod and were bullet proof. efi uses bosch injectors found over the counter in any auto supply store. basicly a corvette motor from 86-87 marinized. some tend to run rich but maintain the inputs and you've got a screemin small block that puts out.

Re: Mercruiser 320 EFIs
 

wait a minute..sonic 30ss..did you test drive the boat in marshfield, ma? excuse my ignorance on the post.

Re: Mercruiser 320 EFIs
 

Not only did I test drive it, I bought it abought 5 1/2 years ago:D

Re: Mercruiser 320 EFIs
 

you bought it from me. how's everything.

Re: Mercruiser 320 EFIs
 

Pretty good, still running the boat. Did you ever get another?

Re: Mercruiser 320 EFIs
 

good to hear. i bought an edgewater 247 center console with a yam 250 ob from brian at ss drydock. i miss the rush but like to fish. i'll get back into one at some point.