Ok, so I bought my first boat in April. It is a 1972 Larson Trihull with a Mercury 850 attached. I have taken the boat out approximately 5 times since I purchased it and it has ran like a champ until yesterday.
It started up and idled great. It went into gear and ran moved nicely across the water. As soon as I crossed the no wake zone, I ran into issues. I put the throttle approximately 3/4 of the way down. The motor started to go, but then fell flat on its face. It would not move at all. It wouldn't open up and I could only go approximately 10 MPH. It kept bogging down.
I puttered around the lake for 5 hours, mainly fishing, and then brought the boat home. The whole time on the lake it bogged down going more than 1/2 to 3/4 throttle, but ran like a champ below 3/4 throttle. At home, I ran it on muffs and it ran like a true champ (even at full throttle). It did not bog down at all while on the muffs. I thought maybe it fixed itself, ya right. So, just in case it didn't fix itself I went to the local marina and got some suggestions.
After speaking with them, I came back home and I ran a compression test. I got 115 PSI in each of the cylinders. I then went out and bought some BG fuel additive (suggested by my Marina) and x4 new spark plugs. I added the BG additive to 6 gallons of fuel (nearly double the suggested amount) and changed all of the spark plugs. I was feeling confident that this may solve the problem, so back to the lake I go.
At the lake, it started and idled just fine. I got past the wake zone and got similar results. This time it seemed to go a little faster, but still the bogging issues. I figured I needed to run the entire tank through the engine to clean it out (with the BG additive). While riding around, the engine would fluctuate and it seemed like it was going to take off, but it never did (it did this several times).
After I drained the first 6 gallons, I switched to my second tank. This time I disconnected the fuel filter (figured it maybe clogged) and ran fuel straight to the motor. Still no luck and lots of bogging and sputtering. We put the filter back on. I then had my friend pump the primer bulb while I got on it (the engine) and "boom" it seemed to take off. We did this several times and each time it seemed that pumping the bulb got the motor running correctly.
So, my question is this. Does that mean its a fuel pump issue? To my knowledge, it had never been re-built or replaced. If its the fuel pump, then why does it run perfectly while out of the water? Is there a way to test the fuel pump? What PSI should the fuel pump be putting out?
If it is the fuel pump, where can I find a replacement? What goes bad in them? I looked everywhere online and cannot find a place to by a new or used fuel pump for my motor. I believe my engine is a 1972 or 1973 Mercury 850 (85 HP), SN 7083192. The fuel pump has the #73433 etched on the top of it (probably a part number). Any help would be great. Thanks in advance.
It started up and idled great. It went into gear and ran moved nicely across the water. As soon as I crossed the no wake zone, I ran into issues. I put the throttle approximately 3/4 of the way down. The motor started to go, but then fell flat on its face. It would not move at all. It wouldn't open up and I could only go approximately 10 MPH. It kept bogging down.
I puttered around the lake for 5 hours, mainly fishing, and then brought the boat home. The whole time on the lake it bogged down going more than 1/2 to 3/4 throttle, but ran like a champ below 3/4 throttle. At home, I ran it on muffs and it ran like a true champ (even at full throttle). It did not bog down at all while on the muffs. I thought maybe it fixed itself, ya right. So, just in case it didn't fix itself I went to the local marina and got some suggestions.
After speaking with them, I came back home and I ran a compression test. I got 115 PSI in each of the cylinders. I then went out and bought some BG fuel additive (suggested by my Marina) and x4 new spark plugs. I added the BG additive to 6 gallons of fuel (nearly double the suggested amount) and changed all of the spark plugs. I was feeling confident that this may solve the problem, so back to the lake I go.
At the lake, it started and idled just fine. I got past the wake zone and got similar results. This time it seemed to go a little faster, but still the bogging issues. I figured I needed to run the entire tank through the engine to clean it out (with the BG additive). While riding around, the engine would fluctuate and it seemed like it was going to take off, but it never did (it did this several times).
After I drained the first 6 gallons, I switched to my second tank. This time I disconnected the fuel filter (figured it maybe clogged) and ran fuel straight to the motor. Still no luck and lots of bogging and sputtering. We put the filter back on. I then had my friend pump the primer bulb while I got on it (the engine) and "boom" it seemed to take off. We did this several times and each time it seemed that pumping the bulb got the motor running correctly.
So, my question is this. Does that mean its a fuel pump issue? To my knowledge, it had never been re-built or replaced. If its the fuel pump, then why does it run perfectly while out of the water? Is there a way to test the fuel pump? What PSI should the fuel pump be putting out?
If it is the fuel pump, where can I find a replacement? What goes bad in them? I looked everywhere online and cannot find a place to by a new or used fuel pump for my motor. I believe my engine is a 1972 or 1973 Mercury 850 (85 HP), SN 7083192. The fuel pump has the #73433 etched on the top of it (probably a part number). Any help would be great. Thanks in advance.
