525EFI Tech Questions?
 

Trying to chase down issues with this single 08 525 not performing. Looking at numbers on laptop and was wondering if it is normal for engine temp. @ 158 to drop 12.6 degrees from idle to full throttle. Also looking at the MAP sensor readings on the laptop are in psi and correspond with Baro pressure w/engine off, at idle MAP reads only 2psi lower, once we full throttle it read close to Baro pressure and slightly higher. This doesn't seem correct to me but would like other opinions. There are no codes, beens chasing this problems since we purchased boat this year.

Anbody? Suggestions?

The temp reading sounds normal. At higher RPMs you are getting higher sea pump pressure, thus higher water flow.

As far as the MAP, I'm seeing the same thing with the engine off. I don't have my recording files handy so I don't know what it reads when running.

Thanks Dave for your input, I would appreciate your info from your recordings. I'm starting to think maybe I have a internal vacum leak. Would like to know what kind readings you have to help determine my low performance.

i can't speak to the map readings... the factory workshop manual will have that curve for you to refer to... but the water sounds cold to me. and if its cold, then its rich and if its rich it will not only run average and all the other parameters will try to adjust to deal with it. i don't think 158 is warm enough to get the injection to lean out where it belongs...

Funny you should mention that. I've owned this motor for less than a yr. and thought the same thing. I believe this motor has a 160* t-stat. Every other EFI motor I've owned ran about 170-175* regardless of air or sea water temp. My motor typically runs around 150*.

The motor runs great, no codes, no soot, or fuel smell. I do have pretty high water pressure, around 35 PSI depending on speed and trim. I'm running a DWP XR w/ITS.

there won't be a code... the motor doesn't think anything is wrong... it just thinks it hasn't warmed up and keeps everything at FA ratio that it thinks a cold motor wants... none of which is good for a motor if its run that way for a long time and those settings are certainly no good for performance.

i would fix whatever i have to fix to get the temps where they belong , put a fresh set of plugs in it and see what happens. if you put a new tsta in it, don't go drilling holes in it or anything. leave it stock

I also was thinking the same way, I believe somewhere I read it should have a 160 stat. Maybe previous owner drilled holes? Does anybody know for sure what temp it should be?

i ran my 502 mpi's at 175 and would have gone to 185 if i could have figured out how to do it repeatably... and you have to know if your gages are good. the other thing i discovered was that the electric gages ( mine were gaffrig) are absolute scrap. you get 3 dif ones w/ 3 dif senders and throw them in boiling water and get 3 different numbers 10 deg apart... what WAS accurate was the scan tool.

i ran my 502 mpi's at 175 and would have gone to 185 if i could have figured out how to do it repeatably... and you have to know if your gages are good. the other thing i discovered was that the electric gages ( mine were gaffrig) are absolute scrap. you get 3 dif ones w/ 3 dif senders and throw them in boiling water and get 3 different numbers 10 deg apart... what WAS accurate was the scan tool.

My 525 EFI runs hotter than 158. It is usually in the 170 range.

I have twin 2004 525 EFI's and both temps run almost identical at just over 150 on the gauges and have always run there. Once they are both warmed up they rarely budge from there except occasionally after coming back to idle after a long run. I had a fuel consumption issue on my port engine and believe it may have been the duty cycle voltage. A buddy of mine found and corrected the problem and now they both burn the same again.

My gauge showed close to 160, but did not show a drop like the scan tool did. On the scan the temp would drop as soon as you hit full thottle and continue to drop down to 144 in a matter of 10 seconds. I talk to a marine mech. and he said that its because of the increase of lake water coming in. I was thinking the stat should keep it closer.

That sounds like the way my 525 behaves. Mine is a 2005 model year.

BTW, the numbers I am stating are coming from my Smartcraft guage. I have a temp guage but it does not have numbers on it, just lines. But, the guage pretty much stays on the same line once the motor warms up.

Quit dumping you empty margaritas in the engine room!
 

What kind of water temp are you boating in when these temps drop to 144? What is the size and type of boat this engine is in as boat loadings on the engine can have a big effect on what temp the engine runs at under loads. I have sometimes seen lower temps on bigger power engines in smaller boats.
Its not a huge job to drain the coolant level down and pull off the heat exchanger and check the thermostat itself. Look at the bottom of the thermostat and see what temp unit it is.
If its stuck partially open it can be a problem or opening to soon.
You can put the thermostat in a pan of water, heat the water in the pan and with a good accurate thermometer you can track and observe the thermostat actual opening and closing.

Best Regards,
Ray @ Raylar

Thanks Ray! In my case, it's a stock 525efi in a 30' boat. I can run for miles at 4K + RPMs and my temp will stay around 150. Lately, the air temp is 80+, and the water I'm running in is probably in the 70-80* range. ANY, efi motor I've owned has run around 170*, even when the air and water is cool. This motor is new to me so that's why I'm wondering. I guess I will just replace the t-stat and see what happens. I'm due to replace the coolant anyway.

We are in 80 degree water, temps come down from 158 to 144 in we throttle up. Dave, did you ever check your map readings?

I check those readings tonight when I get home.

Yesterday my temp got up to 167, that's the highest I've seen. It was after about a 15-20 mile run, I came into a creek and came off plane. The water in the creek is much warmer than the main stem of the river.

I'm wondering if my temps are low due to high water pressure. I'm usually running 30-35 PSI.