2003 DF70 RPM Issue and new to 4stroke

[Ymmit07]

Hellp all,

New to me 2003 DF70. I purchased my boat at the end of fall last year. We took it our to test it and it ran great. I have a 2" thick folder from the previous owner of everything that's ever been done to the boat as a unit. Problem is the folder was when his dad owned the boat. The boat sat the last two seasons until fall when he wanted to take it out. It wouldn't start and he took it in. They replaced the HP fuel pump & Fluids. I filled the tank with non-ox fuel and a can of sea-foam before we tested it before we purchased.

Now this year I hooked up the hose and started it up and it idled great. We have been out 4 times in the last few weeks.
First time out it ran like a champ.
Second started and idled great as i got up to full throttle and on plain i noticed the RPMs were low and then it rev'd up to the normal 5k range and would intermittently bog and then be normal. The other thing i noticed was a small fuel patch from the motor after i shut it down. it does go away after a bit. I opened the fuel cap after stopping thinking maybe it was vapor locked. No issue and ran like a champ,
3rd time out the very next day and no issue.
4th time out tonight the problem came back and seemed worse, bogged down a lot and even at half rpms.

The only difference is the tank is at half which is when it seemed to start.
The motor starts fine every time and idles great with no issues.
Could this be the plugs, fuel filter or, fuel issue? Im knew to 4stroke and built in fuel tank. any help will be greatly appreciated.

Thanks,
Tim

[catacom225]

Tim . It sounds like your tank may not be venting, was the primer bulb deflated?. There is quite a lot information on venting and anti syphon valves on this site

[Ymmit07]

No the primer bulb wasn't deflated. After hooking up my hose and and letting the motor run for a bit at idle i started to get fuel mixed with the water out of the exhaust. I let it cool for a while then i pulled each plug individually. 1-3 all looked the same with carbon deposit. #4 though, part of the ceramic insulator on the center electrode was red. which im presuming to be worn.

On a side note, since you mention venting. i do occasionally get the smell of fuel when opening any compartment. Im a total newb with built in fuel tanks. The boat is a 16'6" Lund Pro Angler. any o=idea on things to check?

Thank you for your help.
Tim

[tommybe1]

bogging

I have recently purchased a lund boat with a df50 which also sat for a long time.
It has the exact same problem your dealing with. I think I'm on the path to getting it fixed. I found a milky white goo in the water separator filter(You do have one right?)and all fittings I could get to, haven't pulled the manifold yet to get to high pressure pump/vst. Removed the valve that comes from the tank , put a straight thru fitting, cleaned others, replaced filters, haven't taken it out yet but will let you know if that takes care of it, hope this helps and good luck

[Ymmit07]

I havent a clue if it has a water fuel separator. I think i need to open up the floor and to get a better understanding of the fuel take and check everything. The RPM fluctuation comes and goes. Im going to try new plugs first.