Merc 470, makes it a ways from the ramp, but can't make it back. Get 2000 rpm max...

[montejw360]

Hi, new to the forum. Just bought a 1980 Glas Ply with a Merc 470. The Merc 470, makes it a ways from the ramp, but can't make it back. Get 2000 rpm max...

I've been away from the ramp twice now and had the engine loose rpm's. End up getting about 2000 rpm max all the way back to the ramp. This is about 1/2 hour away from the ramp. The boat got out once last year, I just bought it. It sounds like most of the fuel is 2 seasons old. Seller said he put stabilizer in it. 50 gal tank, I topped it off with about 15 gallons fresh fuel.

After the first time I bought a portable fuel canister and plumbed that into the main fuel supply line, eliminating the main tank. Went out today and made it not quite as far. Started the kicker and limped back towards the marina. About half way back the kicker started to stall out. We pumped the ball on the new tank hose and the motor rev'd up again. We ended up pumping the ball to keep the motor going all the way back to the ramp.

After this trip I replaced all of the fuel lines. None of the old ones looked bad. I replaced the fuel filter on the outboard. Will replace the fuel filter on the main engine when it comes, special order.

I'm wondering if the problem is fuel filters? The kicker runs off the same fuel line as the main motor, it tee's off just ahead of the main motor fuel pump. Can a bad fuel filter look good? There wasn't anything visible in either of the filters. I think I'm going to plug an inline fuel filter in ahead of the tee for the kicker and see if that makes them run. I'm going to install a filter/water separator eventually and probably forgo the main engine fuel filter all together as FRAM quit making them. I haven't found a good source for them yet.

Monte

 

[cr2k]

Re: Merc 470, makes it a ways from the ramp, but can't make it back. Get 2000 rpm ma

Maybe you are sucking air from the OB fuel hose?

 

[sschefer]

Re: Merc 470, makes it a ways from the ramp, but can't make it back. Get 2000 rpm ma

Sounds like the tank vent is plugged. Might have some critters in it.

 

[montejw360]

Re: Merc 470, makes it a ways from the ramp, but can't make it back. Get 2000 rpm ma

Sounds like the tank vent is plugged. Might have some critters in it.

we were pumping the ball on the new portable tank, main tank is not in the system. we also had the cap loose as at one point it looked like it wasn't venting so we just loosened the cap. still had to pump the ball to keep the outboard going.

the vent on the main tank works, or at least it did when I was filling it up. i checked it while i was filling it and it was venting.

 

[montejw360]

Re: Merc 470, makes it a ways from the ramp, but can't make it back. Get 2000 rpm ma

Maybe you are sucking air from the OB fuel hose?

main engine sucking air from the outboard? wow, hadn't thought of that. there isn't a fuel selector valve, the ob is just tee'd into the main line, so i guess it could be possible.

seems like the seller would have had this problem, but he was pretty adamant about the boat not having any problems. guess i'll plumb in a selector/diverter valve.