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View Full Version : 2001 Sea Ray 7.4 MPI not getting WOT



WeekEnd Lifestyle
07-30-2010, 11:42 AM
Help...My boat has the above engine with Bravo 3 od. The engine runs smooth and has no missing.
I took it to Dupert's Marine Service on Lake erie and the mech came out and hooked up a hand held computer thing. Says my ECM shows no bad codes. He listened and said, yep it idles great, reves great. Took it out, best is 4000rpm and motor doesn't sound like it's at WOT. Have trouble getting on plane with just 4 *****s on board. At 1 point I re propped from 24 to 22 which should have taken the WOT from rated 4600 to 5000. Not 1 rpm difference.
Well the Mech. changed my plugs, wires, dist and rotor, fuel water seperator, tested the fuel pressure, checked comprssion of all the cylinders everything a okay. But still test run 4000 RPM. Tach is correct.
Well he did find that the dwell does not open after 2500 RPM. Stays the same up to 4000 rpm.
So after all this I get a bill for 845 dollars and still nothing. They said mercruiser said it was the ECM module yet it doesn't show up on the testing?
1400 to replace this. Now I am ticked off because plugs, wires, dist cap rotor will not affect wot when a boat is running smoothly. If wires are bad or plugs or any of the other things replaced, it will run rough.
And what if it's not the module? What else could do this? Any suggestions.
He did say something about the anti knock not showing up and gently used a hammer on each side of the engine with the hand held computer hooked up.
Any Ideas? Can the ECM be rebuilt? Upgraded? HELPPPP I am retired and don't have this kind of $ to keep guessing.

Thanks alot

Gator

makomark
07-30-2010, 04:03 PM
What were the results of the tests they ran - numerically - not just A-O-K?? How did they conduct the fuel pressure test and where did they do it?

Given what you have shared, I'd guess on the fuel supply being restricted somewhere. The spin on fuel filter is usually only one of many filters on a MPI setup. On an engine that old, I don't believe the ECU monitors fuel pressure in any manner whatsoever.

There are much cheaper solutions IF you need to swap the ECU - I doubt the ECU is the problem.

Finally, the handheld thing is a scan tool. It connects to the ECU and allows you to see what is going on. Trouble codes, aka DTCs, are only set when a gross failure has been detected. A sensor could be off but still at a "legitimate" value and can keep full performance from being delivered. Did the mech do a complete check on all the sensors or just a "quickie" check for DTC's?

WeekEnd Lifestyle
08-02-2010, 09:10 AM
Thanks for answering.
He put a gauge on the fuel line and we ran the boat at idle, mid and wot (4000 only).
He copied down all the values that the hand held computer gave him and ran them by mercruiser who supposedly told him that it was the ECM. I looked at my books and it only shows the spin on fuel water seperator for a filter. None in line and no carb so??? He ran that hand held at the dock and uner way. Also the fuel pressure was run at dock and underway.
Mercruiser told them that the ECM controls the dwell advance and it appears it's not advancing past the 27 at 2500 all the way to 4000 rpm staying the same.
I am upset because I just got the bill for $845.00 for basically a tune up on a motor that didn't need it and diagnostics that they didn't find anything.
Replacing plugs and wires/dist cap and rotor on an engine that starts right up, idles perfect and doesn't miss at all under load is not in the repair manual 101. If the motor was missing or backfiring okay, but never heard of those replaced items when a motor is running fine, having anything to do with rpms in the range of 4000 to 5000.
If I pick up an ECM on the net, does it have to be programmed to my boat? I have the numbers from the old ECM unit a Delphi. I keep reading that you need to supply some of the places your serial number of the motor so it can be set to that motor?
Thanks for helping.
Gator

makomark
08-03-2010, 08:58 AM
Did you get any of the readings that were recorded? I'd ask for them as you did pay for them....always good to have some historic data.

I guess you are referring to the ignition timing advance....some are controlled by the ECU and some are controlled autonomously, within the distributor's module.

If you get another ECU, it may need to be reprogrammed....depends upon what is was taken off of. For the most part, as long as it is the same type - MEFI-1, -2...etc - the only thing that needs to be tweaked are the fuel curve parameters. These are driven by the engine displacement. Some of the shops doing custom tuning will want serial numbers while others will want to know engine build parameters...compression ratio, cam specs, etc...I'd line up the tuner shop BEFORE looking for ECU's. They may give you a better deal if you buy one of their ECUs along with the programming. best way to find out is ask a few, check some references, and go with a local shop, if possible.

WeekEnd Lifestyle
08-06-2010, 09:34 AM
Thanks. The problem is finding a local shop.
My Marina, Battery Park, was supposed to hook up their lap top and find the problem this spring when they launched me. Well after some dumb stuff, the mech said he didn't get a response from my boat. Said he'd check and get back. After 2 months I asked them. Oppps they haven't updated the laptop software in 7 years. That's why no response. Still nothing, so I went to Dubbert's in Port Clinton. Told them I thought it was the computer, that engine ran great except the top 1/3 couldn't reach. Next thing I know after a hand held type computer, they replace spark plugs, wires, dist. cap n rotor n fuel water seperator. Thhen the same thing Now they want 845 dollars for this a tune up and diagnostics.
I never heard of the items they replaced changing RPMs. Yes if the boat was missing, coughing, sputtering, but even the mech said it ran great and smooth.
So I am in the process of disputing that bill. I feel I should only pay the standard tune up cost. Even though it didn't need a tune up......
Anyone know a place that sells ECMs at a reasonable price. Most on the net are for cars, even thou they advertise ALL MODELS:(
One even said Merc didn't use Delpi modules...Yet I took the numbers and brand right from mine.....
Thanks Again for all the help.....
Gator

makomark
08-06-2010, 01:34 PM
There's a shop up in your neck of the country owned by a gent named Tyler Crockett. He's got a pretty good reputation based on the posts on some marine hi-perf boards. It's been stated many times there isn't anything he can't do with a MEFI box. No first hand experience here; suggest doning some research and, if satisfied, give him a call.

WeekEnd Lifestyle
08-15-2010, 10:26 PM
Thanks. Any idea how to reach him? Shop name? City he is in?
Thanks a million....
Gator

makomark
08-15-2010, 10:58 PM
Last I heard, his www site is crockett marine engines dot com or crockett marine engine dot com - delete the extra spaces. Where - don't know but know he's in the great lakes region. try a www search on the above. (They post on the offshore hi performance www sites.)