loss of power over 3500 RPMS FYI

chs marine service

Petty Officer 3rd Class
Joined
Jun 29, 2019
Messages
88
i have come across this issue about 4 times this summer and wanted to post it here in case others are experiencing this issue.

boats would run great at idle and under load but when you climb over 3500 the engine would bogg down and stall. and may keep running if you pull back on the throttle but may also die.
i would run the engine with an external fuel tank and it would operate properly.
i have in all these cases, replaced the anti siphon valve and supply line hose.. this has solved the issue.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
46,373
did you check fuel pressure thru the RPM range under load? curious to see what it drops off to
 

alldodge

Moderator
Staff member
Joined
Mar 8, 2009
Messages
40,119
Don't think it's a chain saw, but what motor you talking about?
 

tank1949

Lieutenant Commander
Joined
Apr 4, 2013
Messages
1,736
Check blocked air vent on side of boat. Mud dobbers and corrosion love those small screens. I pulled screen out many years ago that had green crap on it. I had a similar problem as you described.
 

chs marine service

Petty Officer 3rd Class
Joined
Jun 29, 2019
Messages
88
Check blocked air vent on side of boat. Mud dobbers and corrosion love those small screens. I pulled screen out many years ago that had green crap on it. I had a similar problem as you described.
yes, before going to the external tank, i always run the boat with the gas cap off to test,
 

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
12,781
Easy to diagnose Carb System(s), or next to impossible Fuel Injection?
 

kenny nunez

Captain
Joined
Jun 20, 2017
Messages
3,011
Have you ever tried using a 6 gallon outboard tank? That will narrow down the problem to either point to the tank or the engine’s fuel system.
 

chs marine service

Petty Officer 3rd Class
Joined
Jun 29, 2019
Messages
88
Have you ever tried using a 6 gallon outboard tank? That will narrow down the problem to either point to the tank or the engine’s fuel system.
yes as stated above : "i would run the engine with an external fuel tank and it would operate properly."
 
Top