blyguy

Friend has 2003 Checkmate w/ 496 HO. Added 3lb procharger w/ intercooler this spring and has had nothing but problems. Has never had it opened it. Problem: ALARM at full throttle and timing retards. Have taken center out of therm. and still no fix. Have been told only 3 things will make it alarm. oil pressure, water temp, & gear oil anyone know if this is true? Any help is appreciated. Thanks in advance!

Elite Marine

I don't know much about the 49, but what about the knock sensor? Might be the issue.

Dixie Doug

low water pressure,fuel pump screens plugged,injector screens plugged.

Island Hopper

There are many things that cause the alarm. the best way to figure it out is with a scan tool. This may not be related to the procharger set up. If I recall correctly there is only a couple things from the procharger set up, that could cause a problem like this. The kit installed a small check valve next to the MAP sensor to relieve the pressure at the MAP sensor under boost conditions. If this is clogged, or not installed, the MAP will will be to high and go into the guardian mode. Some of the older kits used a "split second" box to change the MAP settings. If you have one installed, it may need adjusting.

good luck, let us know what you found.

blyguy

Kit came with a hoakie set up to releive pressure from the MAP sensor. We have taken the one way valve off and switched it around boat wont even run.. Knock sensor is what we think. Spoke with a dealer that has conections with Mercruiser and they said there is a check valve in the gas line. Tonight we did remove that. We will give it a run on Thursday. Thanks guys maybe some gals for the help!

ccarloss

Island Hopper is correct. I put 35 hours on a 496HO kit with no problems (sold boat). The check valve bleeds boost before the MAP. However, I have heard of 2 others who still had MAP sensor issues even with the check valve in place. As mentioned, I used the kit as delivered with the check valve and had no issues what-so-ever. You may want to try a different check valve or maybe even a different MAP sensor.

blyguy

NO LUCK with the anti siphon valve being removed from gas line. Guys with think possibly it is the plugs, me I am guessing it is the MAP sensor or relief. They are putting new plugs in it on Friday so we will know on Sat. However we did remove belt from the procharger and the boat ran fine (no alarm) other than being overpropped. Thanks

ccarloss

Sounds like a MAP isssue to me.

Just kinda thinking outloud but what is your fuel pressure? Are you monitoring fuel pressure and boost? In your post you mention you've never been able to open it up. Is the FMU increasing fuel
pressure as it sees boost? If not the knock sensor could be retarding timing.
Could have an issue with the FMU/Regulator.

blyguy

Not entirely sure what an FMU is, but yes we are monitoring fuel pressure and boost. Do not think fuel pressure is increasing or decreasing much idle 60 psi under boost 65. When boat shuts down it is about 1 1/2 to 2 lbs boost. Thanks

causin trouble

I know my alarms kept going off at full throttle and retarding the timing and fuel...reason I found was the wrong prop (rpm to high) computor adjusted itself kept hitting 5400 then the computor adjusted itself AND would not let me over 5200 kept trying diff props and found I went up 3 prop sizes to keep her under rev limiter ,..... gonna reprogram ecm this winter for 5400 rpm
Not sure that is your problem but that was mine