[EricSmith2]

Here is what is going on Boat will come up on plane idle and run fine however it will not rev up under load to more than 4800 rpm's I can get 4800 rpm's at a little over half throttle however from there on to wide open throttle I get no response rpm's stay the same at 4800. This is trimmed up rpm's by the way.This is wide open throttle speeds and rpmsProp is a 24 Trophy Has no plugs in itEngine RPM 4800Speed 48.6 MPH gpsEngine 225 Mercury EFINo jackplate in the 2nd hole I thinkWater Pressure 10 Wide open ThrottleBoat 1998 Ranger 519 20 foot 6 inches30 Gallons of Gas 300 lbs of people and gearCompression 100 on all Six Cylinders tested yesterday cold not started since September.I am worried because with this prop the motor should be turning close to 6000 rpm's it is only turning 4800.Now for things that could cause a loss of 1000 rpm the list is long and as follows according to past post on ANOTHER board. The post got more in depth the closer to 1998 I got.While reading this please keep in mind the motor starts, runs, idles, and comes out of the hole great it just will not get past 4800 rpm'sPower Pack/Switch Box,Clogged fuel filter,The Port side of the cowling could of knocked off a coil wire resulting in the engine only running on 5 cylinders,Bad injectors,fuel/water seperator,Sensor telling motor to not turn over 4800 rpm,Bad reed or a "sucked reed",Plug wire to coil loose,Throttle sensor,Siphon check valve need replaced,Fuel bulb needs replaced,Restricted fuel flow,Check valve in fuel bulb,A Wire to "CDM" module needs replaced,The ecu box for the fuel system needs replaced.Thanks and if you have read this far I have to ask will restricted fuel flow really cause a 1000 rpm drop in a motor? If so does this happen very often?And as stated earlier the compression check was done with the motor cold it had not been started since September.The dealer that the lady I purchased the boat from said it would run 60 to 62 mph on the gps and the compression checked out fine. This is not my mechanic. I purchased the boat out of state and it was her mechanic. I did see the bill for this but I did not get it from her. I figured the low speed was from the 24 trophy I thought it needed a 25 to get the speed up to around 65 mph or so.I have had the boat to my mechanic and he says everything test out fine. The only time I have had the motor past 4800 rpm's is the day I got it decarbed I took it to the lake and the motor turned 5900 rpm's took it home and went back to the lake the next day and same thing only 4800 rpm's I know something is wrong the mechanic knows something is wrong we just dont know what. He said he will not just start swapping out parts because he does not believe in it. I dont want to spend that kind of cash either but I do want the motor to run correctly.

[rodbolt]

hello by the fact that you did see 5900 tells me the propis correct. it also tells me odds are there is no mechanical problem. bad/broken reeds affect idle. bad switchboxes and such affect idle. the tps could be bad but I doubt it. what you really need to do is rebuild the low pressure fuel pump. test the fuel rail pressure at the rpm and load of the failure and clean the high pressure pump filter. most ign failures at high speed are not smooth, the motor will usually shake. by the fact that it was sold usually indicates it spent a long time sitting. you may also try running it on a 6 gallon remote tank to eliminate hull fuel systems.I rather doubt the ECU is bad. they just dont fail that often. its time for a methodical testing procedure. you Must have a DVM, the TPS test harness, a high pressure fuel pump and a peak reading voltmeter. then follow the test procedures in the book. the merc EFI tester is also nice but must be used in conjunction with the rest of the test equipment.

[Valv]

Are you sure 100lbs compression is even all cylinders ?It seems a little low to me, I have a 1996 200hp EFI and I have 122lbs each cylinder, motor cold, not started since october.I would check it myself and note if there is some difference between cylinders.

[EricSmith2]

Valv Thanks I have asked and searched on this 100 105 and 110 is what everyone who has the 3.0 liter merc is telling me.and rodbolt thanksKeep the ideas coming pleaseericS

[EricSmith2]

I would like to update everyone about my loss rpm's. I think I may have found them The fuel pressure regulator was bad replaced it and now it will run up to 6900 rpm's However it does take it some time to get there it will now run at 5200 5300 rpm's at WOT and then its like the motor has built up enough steam and the boat lifts and takes off. Is this how it is supposed to work or do I still have something wrong.Thanks For Everyones HelpEricS

[EricSmith2]

This should read 5900 not 6900 sorry about that.EricS