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1973 Mercury 40Hp

Ffmedic166

New member
Since my last posting: Ive fitted a 2010ish wiring both controller and engine. Which worked great. Even had the motor in the water a couple of times and did some fishing. WOT top speed from memory was 23mph.

Present Day: I recent had to buy a starter solenoid. I installed the new one and hooked the wires as they were on the old one. The new part had "s"of which I hooked the wire from the key switch which was the same place as old part, and ground "blk" wire to the "I" side. Turned key and it burnt off the "I" lead ground wire. So I contact the seller and asked if it were defective or hooked up wrong he explained from his notes that I had them hooked right and that it most likely was a defective part; so he sent me a new one. I received that one and after cleaning up and fixing the burnt wires installed it, but I didn't put the black wire "I" back on the lead. Turned the key and it fired right up. So a question I have why would that need to be hooked to ground when the body of the solenoid itself is grounded? Any harm or issue not having installed. My main worry is messing up and burning out more wires.

No since the last time it was on the water which was right at a year it ran fairly great. From what I am seeing in videos my motor does not purr and is not as smooth as others. I went out on the water the other day and it fired up with warm up lever and and idled down to ok, not smooth but slight hiccups and jerking of the motor. Since I was at the unloading ramp I reversed and back out and headed to open water. Past the no wake area I opened it up to mid range and it was running good. So I WOT and it increased speed but from sound of motor it increase rpm but not much and the speed was not there. I checked and made sure I was not carrying water (Ripped cover and Florida rains) and it was not much and within few mins my bilge cleared up almost all the water so the weight is was not issue. Previous times on water this thang haul ass. It not being a fiberglass boat and light lets the 40HP rip.

After putting around and fishing not catching anything but a hard time I putted back to the docks, again I opened it up and still not getting the speed or rpm from what I can hear and feel. it not bogging down or shutting down it just feels like the linkage is not going all the way. I got it home and flushed the saltwater and looked at my prop. Maybe a spun prop, but no that is not it though I do need a new lock nut since the lock washer and nut was loose. Even then the splines on the shaft look great. I just replaced the fuel connectors on the engine side and to the fuel tank. I did have a leak before changing them out and was issue of loosing fuel pressure and every so often having to prime bulb. now its consistent with fuel primed fuel line. So that ruled out the fuel issue.

What could be the issue with the motor not achieving the higher rpm band and speed? Also which has to be related why can't I get a smooth idle and run with this motor?

Mixer screw (On carb) is adjusted for tad rich and optimal running. Ive played with the adjustment a couple times out on the water and no change besides stumbling idling to too rich of a idle. So anyone could help me figure this out that would be great.
 
Your motor is a 402 model that had issues with the center reed valve / labyrinth seal wear from crankshaft wobble. It was a very common problem, some even breaking the crankshaft particularly for engines that were over propped and lugged. Both of the symptoms you describe can come from that wear. Once the clearance starts to increase at that seal, the engine cannot keep the positive and negative crankcase pulses isolated from each cylinder so fuel delivery and scavenging are interrupted causing stalling, poor idle, and weak high speed performance. Also, a leaking upper or lower crankshaft seal can also be a cause for your symptoms. Be this as a last resort because the only way to find this out is to disassemble the powerhead.
 
Your motor is a 402 model that had issues with the center reed valve / labyrinth seal wear from crankshaft wobble. It was a very common problem, some even breaking the crankshaft particularly for engines that were over propped and lugged. Both of the symptoms you describe can come from that wear. Once the clearance starts to increase at that seal, the engine cannot keep the positive and negative crankcase pulses isolated from each cylinder so fuel delivery and scavenging are interrupted causing stalling, poor idle, and weak high speed performance. Also, a leaking upper or lower crankshaft seal can also be a cause for your symptoms. Be this as a last resort because the only way to find this out is to disassemble the powerhead.

would it be worth pulling the power head and basically rebuild. I did think of the reed valves but assume since it not spraying or misting fuel out the front that it was not worth trouble at the moment.
 
would it be worth pulling the power head and basically rebuild. I did think of the reed valves but assume since it not spraying or misting fuel out the front that it was not worth trouble at the moment.

Technically it's not the reed valves, Its the aluminum center main valve body (reeds attached) that the crankshaft rotates in with about .002"-.003" clearance and only a film of oil keeps the two from making contact with one another. As time and hours progress that clearance starts to wear open from the crankshaft wobble that causes the running issues. I have seen these engines with as much as 1/32" wear in the seal to crankshaft clearance and pretty horribly running engine. That engine is not worth rebuilding from a financial standpoint and really not popular with any Merc enthusiasts but if you wanted to tear it down and explore what's going on and learn, go for it. Make sure you have done due diligence that it's not something else thats making it run poorly before going inside.
 
Technically it's not the reed valves, Its the aluminum center main valve body (reeds attached) that the crankshaft rotates in with about .002"-.003" clearance and only a film of oil keeps the two from making contact with one another. As time and hours progress that clearance starts to wear open from the crankshaft wobble that causes the running issues. I have seen these engines with as much as 1/32" wear in the seal to crankshaft clearance and pretty horribly running engine. That engine is not worth rebuilding from a financial standpoint and really not popular with any Merc enthusiasts but if you wanted to tear it down and explore what's going on and learn, go for it. Make sure you have done due diligence that it's not something else thats making it run poorly before going inside.

well I’ve removed the motor off the boat and put in stand. I removed carb for cleaning and thermostat of which it didn’t have one and the “pop it” valve? Anyways. I also took the foot of which was a pita…everything has fused together from sitting in water (prior to me) and I played hell getting impeller which was looked good besides a crack in one fin. I had to chisel the damn brass body off the drive shaft. The shaft itself has major rust on the body of it. The shift rod stayed with the motor and I can’t get them separated, had to chisel the cams to off. They wouldn’t budge. It’s a wonder I was even able to shift and do down the water. Any ideas on how to remove the lower shift shaft? Will need a new one or good used one since I’ve put on it and still can’t get it loose. It’s been a mess thus far. Going to try and post pictures.
 

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Anyone in the Central Florida area that has a blown or parts for this motor hit me up.

Well I could not get the lower shift shaft off so I took the powerhead off and the midsection off the swivel to slide the whole shaft out. Two days of messing with it and I am now further in debt to needing new parts. So much was corroded on. I will post more pics of the progress, but as of now I am dead in the water. no money atm to pay for all the crap that has to be replaced. without another new lower complete unit I am looking right about 500.00 in parts. BOAT= bust out another thousand!

I am seriously thinking of just buying another motor at this point.
 
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