ATOMIC 4 gas NO Forward Power only REverse Power

[lasallehome]

Just came back from trip across lake- top up gas tanks and gas attendant accidentally put diesel in my gas tanks. |But i have fully drained tank- new filters - new gas- new spark plugs- etc and ran new gas for hours at dock- no problem-
Engine revs up well at dock- when I put in reverse it gets a lot of Power BUT soon as I put in forward there is no power- does not go over 3 knots- feels likes it going to stall- it is a 2 blade folding prop new a month ago. and worked fine till last week.
i can go full throttle in forward and it does not increase power in motor at all
Any help appreciated

 

[tommays]

What kind of fuel filter are you using as when i took my A4 carb and fuel pump apart i was supprised it ran at all there was so much garbage in the PUMP and CARB

I was really lucky that the long main jet tube came out and i was able to clean it

Have you removed to fuel pump bowl and carb drain (watch out on the fuel pump) as the gasket does not like to be reused

 

[lasallehome]

I use a sierra or mallory filters- no i did not remove carb or fuel filter- as it had good revs at the dock and good power in reverse- but when i throw her into forward , only goes faster than idle only

 

[higgs]

Check your filter again. Perhaps it plugged up quickly because of the leftover diesel in your system.

 

[lasallehome]

But why would there be good power in reverse only-

I raced yesterday and went aground , when i put it in forward to try and get off ground , it had absolutely no power even wide open, When I put it in Reverse , Icould not even open it half throttle as it was revving too high and needed to slow it down???????

 

[tommays]

Well

Forward is a clutch pack that is most likely working

Reverse is a funky band that clamps around the clutch pack and can SLIP pretty easy if it had any adjustment issues and allow the motor to reach high RPM

 

[lasallehome]

i did forget to mention- that just before this all began- the loss of power- I towed a similar sized boat 32ft into my harbor that also had its motor stop from him filling his tank with diesel- mine only had 4 gallons added- But since i towed him[mine is a 33ft] thats when i LOST MY FORWARD POWER AND NO HIGH REVVING OR POWER IN FORWARD ONLY

 

[sailaway78]

If it makes power in reverse

If it makes good power in reverse, but not in forward, look to the transmission or something in the drive line. I would certainly take a look at the prop, especially since it started right after you towed someone. Maybe the prop pitch has gotten way out of whack. If I were a betting man, thats where I would put my money. No engine, either gas or diesel, knows whether the tranny is in forward or reverse. If it was fuel related, it would have the same response in either gear.

 

[Witzend]

IS your gear ratio different between Fwd and Rev?

 

[MrBee]

Im a bit confused as to what happened and in what order ??
When tou fogure that out you can figure out the most likely cause or at least where to start looking

 

[Kevin3447]

Maybe ask here:
http://www.moyermarine.com/forums/
Maybe before you do, set out your story in order, including towing; and also clarify what you mean by "no power", because I'm confused by your post about running aground - did reverse actually pull you out, or was it just revving high and possibly slipping? Can you get revs in neutral? Maybe you have two problems - no power, and trans slipping in reverse?
Anyway, the more info you share, the easier it will be to find a solution. Moyer Marine is the expert on Atomic4s - I'm sure you'll find help there.

Kevin

 

[Alec]

It sounds like a classic case of the motor running too lean. It will rev when there is no/less load but no real power. I would pull the main jet (at the bottom/rear of the carb bowl) and check it for blockage. If that doesn't help, dissasemble the carb & clean it out. It doesn't take much blockage to change the flow. Simetimes a tiny spec will do it.

 

[higgs]

I go with Ross. Gear reduction into reverse could be a big factor. Replace the filter. Cheap and it at least will eliminate that possibility.

 

[Ross]

In this case check the throttle linkage. It isn't opening the carburator when you shift forward. Is it single handle or two handle engine control?

 

[druid]

Yeah- I'd guarantee the gear ratio in reverse is higher, so it allows the engine to get more revs, more power, more revs...

I'm not sure why diesel would clog the filters - we have filters on diesel engines (some even 2 micron!)...

But I have no other idea as to why diesel would cause loss of power.

druid

 

[RichH]

1. Check your compression, especially noting the differences between cyl 3-4 and 1-2
Towing involves 'lugging' the engine (high cylinder pressures at low to medium rpm) and the A4 is quite vulnerable in blowing head gaskets between cylinders, especially if the head hasnt been routinely re-torqued.
On my old A4 many years ago, I had the EXACT SAME symptoms --- stalling in FWD, OK in REV. and the problem ultimately was traced to a blown head gasket - between 3-4.

2. Pull the carb and thoroughly CLEAN the EMULSION TUBE .... the 'perforated' thin tube that sits over the main jet. The emulsion tube is what primarily controls the air-fuel ratio and if even the teeniest spec of debris gets caught in one of the teeny holes of the tube you can have 'very strange' operating problems. "Bypassing"/broken fuel filters are the usual cause of crap in the emulsion tube.
If you have an adjustable main jet, sometimes you can (temporarily and without carb disassembly) 'lean-out' the emulsion tube by main jet adjustment.