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Fuel Injection Coversion for Mercruiser 350


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9 replies to this topic

#1
SCCA_Racer07

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I am exploring the option of a basic or MPFI for my 95' Echelon with a 350 Mercruiser with 265hp. I have only seen a couple of kits but some are for marine apps and some are not. Anyone have any info on this?

#2
Live2Ride

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What would be the advantage/disadvantages of going with fuel injection?

Edited by Live2Ride, November 24, 2009 - 03:58 PM.


#3
SCCA_Racer07

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What would be the advantage/disadvantages of going with fuel injection?



More power
Smother power
high altitude ease
instant cold start ups
better gas milage
less maintenance
modern
increased value

etc, etc..

Negatives


more parts and electronics

#4
Woodski

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I have also thought about converting my power plant to EFI. You mention that in the positive's category you would get more power, that is not the case. You should look over several different power curves to verify, but converting to EFI will not actually increase the power level of the engine. To accomplish that, you need to add more airflow to the engine. The most effective way to do that is to convert to the Vortec style cylinder head, that is the key change that moved the power curve from 265-280 hp up to the 310-335 hp range of the current crop of boats. Other helpful items include 1.6 ratio rockers, ZZ4 camshaft, less restrictive spark arrestor, cool intake air and you can bump the timing up from 8 deg to 12 degrees to help. I would be curious to see what EFI kit you are looking at for your conversion.

The rest of your list is accurate, you will definitely notice better starting, and if the carb is not well tuned, the smoothness could be affected, particularly off idle. Living in a state that has a wide temperature range, I notice that I have to tune the choke a couple of times a year (bi-metal spring), but other than that, little maintenance is required.

#5
Sunsetter95

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I agree. I thought of going to EFI also. Out here in the west in the summer, the carb goes dry in just one week. It is almost impossible to get the choke correct also. Can you go to Vortec heads and intake on an older block? I already have an upgraded cam and pistons, and have a little over 300HP, but I think with EFI I could get more out of it if the swap will work.

#6
SCCA_Racer07

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Throttle body: http://www.affordabl...ion=show_detail

MPI: http://www.affordabl...ion=show_detail


Also, when I said you will achieve more power I was not saying you will gain lots but.. You might gain 10hp + or - over the carb set-up.

#7
Bake's Marine

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Unless you are really attached to the boat, I wouldn't do it. MPI is the only way to do it in my opinion (there is a good reason why TBI engines are not available anymore)

$1500-2000 in parts is not worth the upgrade especially on a non gen+ motor (before vortec)

Save the cash and upgrade to a late 90's boat. Gen+ motor and 320+ HP MPI engine.

-Paul

#8
SCCA_Racer07

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Unless you are really attached to the boat, I wouldn't do it. MPI is the only way to do it in my opinion (there is a good reason why TBI engines are not available anymore)

$1500-2000 in parts is not worth the upgrade especially on a non gen+ motor (before vortec)

Save the cash and upgrade to a late 90's boat. Gen+ motor and 320+ HP MPI engine.

-Paul



Paul- Could not agree with you anymore. That's why I was just exploring the idea. Thought maybe if I could pick up a used kit somewhere for under $1K it might be worth while. My carb is just going to need to be replaced in the next few years and I thought for a little extra money I could upgrade.. With that, if anyone comes across one let me know:)

#9
Woodski

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Vortec heads can be installed on an older block, the tricky part is the intake manifold as the intake bolts are not the same pattern or specifically angle. There are several aftermarket Vortec type heads also available, but you actually can get a set of Vortec's pretty cheap now. They come on '96 and newer pickup trucks, so any junkyard will have a set of them.

Just to reiterate, you will not gain any power with a FI unit, and in many cases will actually end up with a bit less. The carb on the boat in question is a 750 cfm Weber, it actually flows very well. The air consumption at 6000 rpm on a small 350 cid engine is 600 cfm. It will be the other elements that you will find your returns, cold starting, transitional performance characteristics and probably smoothness if you don't keep the carb tuned. Sounds like in the land of dry heat, you have to fill the floats every week due to evaporation. The high pressure fuel supply of EFI solves that problem. FYI, my boat has around 400 hp and the carb is still not a limiting factor, actually the hull and wetted area is the limiter for top speed.

I totally agree on the value aspect, it is very hard to justify dropping north of $1k to improve the performance elements that are really the least used in a ski boat application. Basically, you run the boat at idle, 18-22 mph (if you board), 30-36 when skiing and 40-42 when footing. Not too many accel's and decel's other than getting up and turning, so really you run the boat at steady state most of the time. If you want a fun project, have the time and $, great, that is probably why I would ultimately do it, more for the fun and get one that I can tune and play with.

#10
the_dude

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There is way to much value being placed on "vortec" heads in this thread in my opinion. Almost any aftermarket head, weather designed for the Vortec style intakes or not will positively destroy a factory vortec head out of a wrecking yard. Plus not all factory heads are made equal.

I don't think you really need a "marine" based system as long as you can find a spot for the ECU that will stay dry. So I'd look at the older holley or edlebrock units if looking for a used system on the cheap. Don't waste your time on a non MPEFI. I like the Edlebrock pro flo system better of the two. I've also used the Holley commander 950 based systems but I'm not a big fan of them even though they have greater tuning potential. Both of these systems are old enough you could find used ones and there is a newer generation of systems coming out now that might mean lower prices on those ones.

Also, to echo what was mentioned above, you are not going to see more power from EFI compared to an equally equipped carb motor unless the carb is not tuned properly. All the other things you mentioned you will get.




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