Repower....7.4 carb to fuel injection question

mstang64bb

mstang64bb

Member
Jan 3, 2013
186
North East Connecticut
Boat Info
1988 Sea Ray 268 Sundancer
Engines
454 w/ bravo II drive
Hi All~
My wife & I like the size and style of our old current 268. She is in great shape. This fall we plan to reupholster the seat cushions in the cabin and cockpit.
I have 680 hours on the original 7.4 engine. It still runs great, I just do not feel comfortable taking any type of long journey. I'm want to least replace with a remanufactured long block and add a closed cooling system.
If possible, I want to know if any one can explain to me what's involved to convert from carbureted to fuel injection? I have a lead on a complete 7.4 MPI with very low hours, but not sure what else is required/needed besides the engine to make it run, ie- some type of onboard computer, such as automotive applications.
Any help would be greatly appreciated....
 
Get as much of that pkg. as u can, wire harness, ecm, everything, otherwise the conversion could nickel and dime you to the point it wouldn't be worth it
 
if it is a complete package, you simply plug it into your wiring harness and everything works.
 
In 2005 we purchased our boat with twin 454 at 650 hours. The engines now have 2500 hours. They do not use oil and the boat goes just as fast as it did. I did 1 tune up at 1300 hours. Time for the next. Change oil every 100+ hours some times it goes to 130. Change transmission fluid every 2 years.
Unless you have a problem with the engine or a Mechanic looked at it and said it is worn out I would consider keeping it. If you run it at 4200RPM all the time it could be time for a new one if run it at 2800 RPM it probably has a lot of life in it.
I asked at the Seattle Boat Show in the winter the Merc people and they said if I change the engines keep the same type because if I change to fuel injected I will need to change the throttle linkage.
 
If the engine is a 7.4 MPI with MEFI-1, -2 or -3, then, since the ECU is mounted to the engine, and the engine uses a returnless fuel system, it's pretty much a drop in replacement for the carbureted engine. I don't think they made any 7.4s with the MC555 ECU, but if they did, interfacing the gauges might be an issue. That not the case with engines that have the GM MEFI module.
 
Scoflaw, I am familiar with the 7.4 MPI's in both standard and Magnum configurations, as well as 496's and previous generation 502 EFI's. I have done a number of these swaps. It is very straight forward. Any 7.4MPI will work in the 268 without mods to controls, gauges, wiring, motor mounts, etc.

Simply plug the MPI into the wiring harness in the boat, and everything electric will work including instruments. The shift and throttle linkage will work as well.
 
Gentlemen~

Thank you for your great insight. I will double check and make sure the ECU is mounted to the engine. Otherwise it looks like it may be a go. Of course I will want to hear it run and really check it out. I can them decide on this, or just replace mine with a new long block.
The reason I want to change is not only the fear of many hours on my current engine, but corrosion from the salt water. I want to go with a closed cooling system to increase engine life. And, the added upgrade to fuel injection is a plus. The engine I'm interested has very low hours and is suppose to be from a fresh water boat.
 
Maybe I shouldn't worry. My dock neighbors all thought that it was a lot of hours combined with the age, that I am asking for a failure to happen. It seems that most of your post replies agree that my current engine should be just fine. I do take meticulous care of her. She runs GREAT! I thought I was headed for trouble if I didn't make a change.
Thanks for the great replies. I get to save my money!
 
mstang64bb said:
Maybe I shouldn't worry. My dock neighbors all thought that it was a lot of hours combined with the age, that I am asking for a failure to happen. It seems that most of your post replies agree that my current engine should be just fine. I do take meticulous care of her. She runs GREAT! I thought I was headed for trouble if I didn't make a change.
Thanks for the great replies. I get to save my money!
Click to expand...

You really shouldn't worry.

I've got two of these in the back of my 340 and have made 2+ hour runs back and forth (about 5 hours total) from Cleveland to the Lake Erie Islands at least once a year for the last three years. My engines just rolled over the 600 hour mark so they are not far behind yours. Both guys on the last trip complemented me on how nice the engines sang. One has a Sea Ray about 10 years older the other one, about ten years newer.

If you want to get some piece of mind, do a complete tune up. Wires, cap and rotor and coil. Have the carb rebuilt if you have any concerns about them at all. Do all the fuel filters and an oil change with filter. That way you have a baseline. I don't think your engines have even hit mid-life yet. Enjoy! :smt038
 
Northshore~

Thanks for the vote of confidence. I do keep the engine tuned and regularly maintained each year. She does run beautifully.

Where in Cleveland are you from? I am from Ohio as well. My family live in Willoughby, and we would put the boat in at Wildwood Park. I use to live in Fremont and travel to the islands from Port Clinton all the time. Boy... the stories I could tell you..:grin:

Thanks again..
Bob
 
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