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View Full Version : 04 merc 250 efi issue



shores
07-12-2016, 09:02 AM
Just picked up a 24 jaws with a 04 250 merc efi. 23 mirage.

Starts idles nicely I guess. Been awhile since I've had a big 2-stroke. I've had some 225 dfi's in the past. 1 single 20' CC 200dfi. 3 different twin 225 26' CC's.

In and out of gear nicely. on the initial push on the throttle it picks up nicely from idle to about 1200rpms and then gets "flat" feeling. It's revving up but enough lag ot make you notice it. Continue pushing to WO and it just feels about the same, then at just over 2k rpms it gets up and goes. This takes a few seconds. After 2k rpms or so, it's gone. Runs out in the 5k range, didn't get a chance to air/trim it out in the water I was in at the time. I do not know the boat and there was traffic in the intercoastal. She ran 46mph at about 4k. I saw the past high # on the Garmin and it was 62.2. That seems a bit far fetched as I have read they run 58 with a 23 mirage.

Now, I only spent an hour driving it so my trimming and playing around time is very limited. Several idle to plane runs and every time I went to plane, that same 1200-2k rpm lull was there. I fed it slowly, same result. Threw the stick right down, same result. Run it down to 3k rpms while running and hit it, took off. I did not get to play with trim tabs when planing off. I did have the engine mostly tucked.

I want to say something is not right on the low end over 1200 but it's so consistent, it makes me wonder if this is just the nature of this engine/prop on this size boat coming out of the hole.


Thx for any help. :thumbsup:

XstreamVking
07-12-2016, 09:09 AM
Most likely a fuel starvation issue. Filters in the VST can become gummed up, pulse pump might be weak. Weak coil could also be the culprit. I would start by cleaning the fuel system and check filters then do a spark check. As far as props go, these motors are tractors with a ton of low end torque. Over propping should not be an issue.....They like 5500 for a top end rpm.

shores
07-12-2016, 10:53 AM
I talked online with someone that has this same boat/engine/prop and his does this. He said it has to do with the way the throttle moves. There was a bulletin for the roller on the throttle for the efi's.


I've never cleaned a VST. if there was a video, I'm sure I could pick up on it. merc filter on engine looks fairly new and the separator on the boat is a clear bowl and look clean.

mikeylarge
07-12-2016, 10:56 AM
The vst on that motor is very simple. Dont be afraid to take it apart

shores
07-12-2016, 12:25 PM
Looks straight forward. Not sure why that would affect such a small rpm range but I don't know much about these so I'll dig into it.

vnemous
07-12-2016, 12:47 PM
You may have a problem but my history with these 3.0 efi is that they are kinda sluggish below 3000 rpms. Wot should be around 5850 with that motor. JMO

shores
07-12-2016, 01:02 PM
I honestly don't know if it's the prop getting going or something else. What would be the next size down for this from the 23 mirage plus?

vnemous
07-12-2016, 01:05 PM
I would look around and see if any has a mercury trophy you could try. They are 4 blade with 13.75 diameter which makes them pretty easy to spin. Jaws I believe are much like most 27x7 boats and a 24p might be a good start. You may want to leave the vent plugs out so you can vent the prop to let the motor spin up. JMO

Velocity72
07-12-2016, 02:06 PM
Vented Trophy Plus and clean filter.

Never had any linkage issue with mine.

shores
07-12-2016, 02:42 PM
23 3'blade mirage plus to a 24 4 blade? That doesn't make sense?

it is indeed a 24'7"x7' plus bracket. I think this would be a neat boat with another foot of beam.

This mirage has no vent plugs.

I'll have new champions tomorrow and I'll dig into that VST and see what it looks like. IOMO, I don't think it starts up 100% right. My DFi engines jumper to life when cold. I haven't touched the primer prior to any cold start yet but when I checking batteries. I did give it a few squeezes and it didn't get hard.

vnemous
07-12-2016, 05:14 PM
The 24 trophy is probably the most popular prop on 24 super boats with 3.0 from 225 efi to 300x JMO

shores
07-14-2016, 09:35 AM
Cold compression #'s. 1 seems off. 5 holes are 116-118 and 1(port middle) is 105.

shores
07-14-2016, 10:14 AM
ok, so decided to just warm it up on the hose for a few. Ran the #'s again. The cyl was just over 100-102. The others where at 110.

It had NGK plugs, I put back in new Champions. The gap was thin on the NGK's. The stock Champion was .035 so I left them at that. All the NGK's looked identical. Initial and restart was faster on the Champions, IMO.

vnemous
07-14-2016, 12:01 PM
comp on that motor is about 105-110. Yours sounds fine.