Purchased first boat, have issues-Help!

[gunfun13]

Purchased a used boat last week. When the previous owner started the boat for me I noticed it seemed to crank a little slow, but didn't think much of it at that time..and batteries were on a charger. A couple days later I tried starting at home and would barely turn over but after several attempts it turned just enough to start. I thought the batteries might be low, put them on a charger and tried again the next day. This time it wouldn't turn at all and just click once when turning the ignition. Knowing the batteries are charged, and the prior events of slow crank turning into no crank..I concluded it was a starter problem, so I installed a new one. Go to start and "click". I then jump wired the starter and it fired right up. Shut it down, went and turned ignition and it fired right up. So I trailered to the lake, went to start, click. Jump wired it and headed out. Ran for a while, shut it down, shortly after turn key and fired right up. Headed to a different spot, fished for maybe a half hour, turn key..click. Jump wired it and headed back to the ramp. Any suggestions to remedy the issue? I've checked terminals for corrosion and everything seems clean.

2nd issue. I am getting a popping or backfiring starting around 2000rpm. It starts easily and runs smooth up to that point, and can rev beyond that in neutral without issue...only occurs under load. One friend suggested bad plug wires, another bad gas. Any suggestions? I will be installing new plugs, wires, cap and rotor this week.

Boat is 1984 22' Pursuit with Volvo Penta aq225d.

[sherman51]

the cranking problem could be a bad solenoid. they only cost a few bucks. it would be worth the investment to replace the solenoid. the tune up could take care of the running problem. if the tune up doesn't fix your problem then its time to do a compression check.

[mrhookup]

are the batteries old? they may be struggling to hold a charge for an extended period of time meaning they are no good, could be why the previous owner had them on the charger when he ran the engine for you, sound like it'll start when jumped but after fishing at a specific location with the motor off they die...may be something to consider.

[gunfun13]

are the batteries old? they may be struggling to hold a charge for an extended period of time meaning they are no good, could be why the previous owner had them on the charger when he ran the engine for you, sound like it'll start when jumped but after fishing at a specific location with the motor off they die...may be something to consider.

I had the batteries tested and they are good.

[Hooter]

Make sure all the connections are good, positive and negative side. Perform a"volt drop test" through the entire circuit. (Google it). Key switch to the starter. As well as the big power cables from battery to the starter. Doesn't hurt do test the amp draw as well.

[gunfun13]

Looks like I have things resolved. Put new connectors on the solenoid control wires and that seemed to fix the starter problem, then while putting new plug wires on last night I found out 2 were reversed.