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    Mercruiser 5.0 50 degrees at idle

    If there is an issue with timing/runnability on a thunderbolt ignition with sound fuel delivery the most likely culprit is the ignition sensor in the distributor. So many I've replaced over the years. Go oem, three wire with a dedicated solid ground to same post/stud on flywheel cover as battery...
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    thunderbolt IV module question

    Good info, appreciate the beta for module operation over the years. Yet, I find using the latest style sensor, three wire fully potted with large/long ground terminal/wire with old, your definition "Gen 1" (which BTW isn't the original style module, mie 454's used a thunderbolt iii style...
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    Transmission Woes in Vintage Mercruiser

    Sweet boat Not too familiar with the EZ shift mcm drives. I only worked on one and it was painted a metallic light green, same with the Renault engine coupled to it. My first observation was how it resembled an alpha drive but was 80% the size. Everything worked fine and it was a basic...
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    Mercruiser 5.0 MPI #3 cylinder ignition miss

    Yep, think your buddy in the tube getting pulled around at a reasonable rpm, just enough to be on step with a bit of trim for handling. This scenario is how your boat, engine, drive and related power supply systems operate. Yer car just gets you to 70 and then the motor chills, overdrive n...
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    thunderbolt IV module question

    I know this to be true with next generation (plastic housing) style modules but afaik the older style may or may not have mapping for advance from v6 to v8. I would guess not, I was told many years ago by a fella who's forgotten more about boats than I can learn a v8 stamped module will work...
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    thunderbolt IV module question

    Like Scott said, yes/maybe? Don't know much about the old large box, riser mounted units. I see a few of them these days but can tell you rn I don't trust them. Look at the back, potted side of the module, is it cracked anywhere? If so, move on, 50/50 chance of it lasting much longer if it even...
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    2005 Bayliner Capri 175 wont stay running

    Nice, Check the tune up items as well, never a bad idea to put new spec plugs in
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    Mercruiser 3.0l TKS stalling

    If fuel is dripping from the venturi supply at that rpm there is a likely blockage somewhere in the carburetor. Time to tear down, clean, inspect and install new carburetor components. The tune up stuff your doing as well is great, part of routine maintenance
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    Fuel pressure loss on Mercruiser 140

    Mid 70's Chrissy sport fish 32. Replaced the old chris sbc with brand new merc 6.2 mpi. Customer complained that higher rpm engines starving of fuel. Found chris craft during that era used a perforated pick up tube in lieu of an anti siphon valve. Mechanical fuel pump could overcome the vacuum...
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    Mercruiser 5.0 50 degrees at idle

    Make sure you're on #1 compression TDC, could be you're on the exhaust stroke and possibly wrong firing order. A LH rotation sbc will run at multiple firing orders, I've seen it. Once tried to get a reman engine running right and based on vintage/frankenmotor status tried many different firing...
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    Mercruiser 5.0 MPI #3 cylinder ignition miss

    I belive pointed questions are the only ones to ask in this forum. The issues deserve concise answers with pertinent info regarding analysis and repair. e.g., I wouldn't recommend a member replace the prop due to a no start issue....the direction does require knowledge of known situations and...
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    Recommend a dwell meter

    Definitely go with an analog one if you can still find one. I got lucky in procuring mine years ago. I've never had much luck using even a quality digital multimeter for setting dwell, ymmv
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    5.0 mpi backfiring through exhaust. Won’t start

    1-8-4-3-6-5-7-2 standard sbc LH rotation engine. Flat cap may have numbers cast into it but you need to ensure the #1 position on the cap is indeed firing at #1 compression stroke. Once set the cylinder numbers are the above mentioned order of firing
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    Mercruiser 5.0 MPI #3 cylinder ignition miss

    Your car is not your boat, other than same theory of engine operation there is very little to use as a comparison between the two. You can do what you like with your boat and asking questions related to your boat will garner quality answers from experienced persons on this site. Nobody is...
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    Fuel pump not working

    Primer ball is not required for sterndrive/inboard engines. In fact it can cause a restriction before the fuel pump and cause poor performance or failure of the pump Iirc Volvo powers the fuel pump off the alternator in some instances, may want to double check your wiring at the alternator...
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    Mercruiser 5.0 MPI #3 cylinder ignition miss

    Tune up parts are supposed to changed on a regular basis. Engine hours or number of seasons, whichever spec is reached first. I understand the theory of just "throwing parts at it" and agree a diagnostic tool is necessary for some issues. It has helped you locate an issue that many boaters...
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    Fuel pressure loss on Mercruiser 140

    You bet, one other thing you can try if you're leery about breaking the fuel pick up is to run the engine on a known good remote tank and check fuel pressure under load/rpm
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    5.0 mpi backfiring through exhaust. Won’t start

    There is no procedure for setting the timing on a merc mpi with a 555 ecm. Guessing this is the setup based on provided info. There is a procedure for properly installing the distributor but I don't feel we need to go there just yet. OP: you need to verify good clean spark, firing order, and...
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    Leak from "Lower/upper shoe"??? HELP!

    Never said otherwise Pics or it never happened
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    Fuel pressure loss on Mercruiser 140

    This And, no worries on heating the tank fitting. A heat gun will suffice, just make sure there are no initial leaks. 3/4" wrench is common size for tank pickup fitting
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