70's? Chrysler 70 HP fuel problem?:confused:

[Waddells]

Hi I just brought an old chrysler outboard and its a little hard to start cold, normally needs help with aerostart into the carbs then runs fine. I can get it running at full throttle for about one minute then dieslike no fuel but runs at half throttle fine. then if i let it idle for a few minutes i can get full throttle for a bit again? an ideas? thanks for any help.

 

[JDP]

Re: 70's? Chrysler 70 HP fuel problem?

Sounds like maybe your fuel pump is bad. Has enough to keep it going at lower rpm's but fails to supply fuel at WOT. Are you running this off a portable fuel tank or built in? If it's a portable tank do you have the vent open? Also check your carb floats. And if the motor has sat for a while a carb clean/rebuild is probably in order.

 

[Frank Acampora]

Re: 70's? Chrysler 70 HP fuel problem?

Yep! sounds like a fuel pump diaphragm. Part is available through local Merc dealer. If he can't find it tell him to look up any 75 horse Chrysler or an 85 Force--bolt holes are a little bigger but other than that, the diaphragm is the same.

For the cold start: pull out the chrome lever on the side of the control box. Advance throttle lever until it stops (fast Idle position) Push key in while turning (to start) to choke engine. Release when engine starts. Leave in fast idle for a few seconds or until engine warms up enough to keep running at idle position. Return throttle lever to straight up idle position and push in chrome button. Throttle and shift will now work normally. You do know to squeeze the primer bulb in the fuel line to fill the carbs for the first start, don't you?

 

[Waddells]

Re: 70's? Chrysler 70 HP fuel problem?

Re: 70's? Chrysler 70 HP fuel problem?

Thanks, the fuel has been replaced and the pickups cleaned. Yes i prime the fuel through first. Tracing the fuel lines i can not find a problem but i removed the outline from the fuel pump and what i think is low pressure coming out. I'll try and replace the diaphram. Is the pump hard to replace? Thanks very much for the help already given. i'll just keep trying.
Thanks

 

[steelespike]

Re: 70's? Chrysler 70 HP fuel problem?

Re: 70's? Chrysler 70 HP fuel problem?

Fuel pump rebuild is a straight forward repair for the mechanically inclined.
Keep in mind there are likely small valves and springs involved.Operation is simple as the diaphram pulses it draws fuel in through the one way in valve < and pushes fuel out the oneway out valve >.

 

[Waddells]

Re: 70's? Chrysler 70 HP fuel problem?

cool, so it wouldn't too hard then. I wish they told everyone about this site as soon they buy a boat. at a guess would replacing the diaphram make for easier starting when cold?
Thanks everyone for yourhelp you have been invaluable!!