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Mercruiser 5.7L Fuel Pressure Regulator ?

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Mercruiser 5.7L Fuel Pressure Regulator ?

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Old 05-12-2022 | 07:45 AM
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Originally Posted by SB
I believe there is a 30psi keihin nr-1 and a 43 psi nr-1. So, be careful.
Yeah. I think with the OEM part only being 179 and coming with the o ring and filter, I'll just get the right one. Irwin can have it for me tomorrow.
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Old 05-12-2022 | 07:51 AM
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Okay, here you go honda fpr and everything including an install mess up to avoid. Lol.

https://forums.iboats.com/threads/lo...ag-mpi.720696/

Alldodge, you get around. :thumbs

Last edited by SB; 05-12-2022 at 08:25 AM.
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Old 05-13-2022 | 04:49 PM
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Old reg would go to 19 psi with key on (Priming. Not starting) t. New reg goes to 43! Bad reg. Haven't started it yet. I think I'll wait for the fuel that I spilled to dissipate first. No idea if this will fix my hard cold start, but it was certainly an issue.
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Old 05-13-2022 | 08:18 PM
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So I think I found my low fuel pressure problem. Now FPR brought me right to 43 psi. I opened the old one up and found a bit of a mess.


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Old 05-13-2022 | 08:39 PM
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Looks like plow trucks frames and rocker panels up here. Yikes !
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Old 05-13-2022 | 08:45 PM
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From: Omaha, Nebraska. Boat on the Mighty Mo! Longest river in the USA!
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How is that even possible even in salt water? I replaced one this week because one engine was running 300 RPM lower than the other. I’ve been chasing this for a year. Computer throws no codes. I have recorded both engines and they both run the same.
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Old 05-13-2022 | 08:56 PM
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My thoughts are that the vacuum line fell off at some point or seawater was drawn in at the connection. It is a very loose fitting vacuum port. I know the PO had a bilge flooding event while fishing. I know he rinsed and cleaned the bilge and motor after, but you'd never rinse this out.
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Old 06-01-2022 | 06:44 AM
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I'm happy to report that the new fuel pressure regulator solved the cold start issue 100%. It now just starts right up and idles nicely. Getting my distributor rotor phased properly solved my drivability problem as well. I ran the boat at 40mph and 4300 rpm the other day. ABL thinks it ran at 5-5300rpm at 40, but I think that either he remembers wrong, or his old analog tach was off. The ECU shows the motor having 0.0 hours above 5k rpm.

I do think I should be a bit higher in the rpm range, but I also discovered that the trim limit was set wrong and I was missing 1.25" of ram travel. Before I start looking at props, I'll see if this gets me up higher but I'm not terribly optimistic that it will get me a lot. I have 22 pitch props on now and I suspect I'll need to drop down. I'm also not getting nearly enough lift out of this 23' SeaCraft as I do with my 20' boat of the same make/model with an outboard.
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Old 05-22-2025 | 04:12 PM
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Originally Posted by Basketcase
I'm happy to report that the new fuel pressure regulator solved the cold start issue 100%. It now just starts right up and idles nicely. Getting my distributor rotor phased properly solved my drivability problem as well. I ran the boat at 40mph and 4300 rpm the other day. ABL thinks it ran at 5-5300rpm at 40, but I think that either he remembers wrong, or his old analog tach was off. The ECU shows the motor having 0.0 hours above 5k rpm.

I do think I should be a bit higher in the rpm range, but I also discovered that the trim limit was set wrong and I was missing 1.25" of ram travel. Before I start looking at props, I'll see if this gets me up higher but I'm not terribly optimistic that it will get me a lot. I have 22 pitch props on now and I suspect I'll need to drop down. I'm also not getting nearly enough lift out of this 23' SeaCraft as I do with my 20' boat of the same make/model with an outboard.
I love that you resolved this! ANY advice on my similar situation?? 2007 - 5.7 MAG MPI Alpha/Bravo. Same fuel delivery system. My issue is very hard starts after it's been running then shut down. Only way to get her to start is to push throttle down at least half way while cranking. I put a fuel pressure gauge on rail and got the 38 - 43 bouncing needle while at idle. Once started she runs fine, no issues. Just the restarts are tough. Serial # 0W687532 Tks gang!!
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Old 05-22-2025 | 04:20 PM
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Originally Posted by ranhood
I love that you resolved this! ANY advice on my similar situation?? 2007 - 5.7 MAG MPI Alpha/Bravo. Same fuel delivery system. My issue is very hard starts after it's been running then shut down. Only way to get her to start is to push throttle down at least half way while cranking. I put a fuel pressure gauge on rail and got the 38 - 43 bouncing needle while at idle. Once started she runs fine, no issues. Just the restarts are tough. Serial # 0W687532 Tks gang!!
How old is your distributor cap and rotor? You have the "crab" style cap that can be a cause of hard start problems. They only last a year or so before they get flaky.
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