To all the boat motor experts, PLEASE HELP!!!

Tommy12

Cadet
Joined
Mar 27, 2011
Messages
14
I want to thank whoever helps me with this in advance, because I am stumped. Me and my brother are pretty good shady tree mechanics, but we we can not figure this problem out. We have totally restored a 18 ft aluminum boat with a 1983ish (no model number nowhere)175 Johnson with a jet prop on it. When we took it to the lake it would not start too good when it was cold. Once we finally got it started and warmed up, you could turn it off, and it would fire right back up. It seems like the timing may be a little off also. The main problem is when we do get it started and give it gas, it will come out of the hole like a mad man, but after about 8-10 seconds of WOT, it loses well over half it power. It is like it gears down. If you stay on the gas it will come back in about 10 seconds, but will lose power again shortly after. I was wondering if the Jet prop was cavitaing or if it is a fuel problem. I know it needs a new choke solenoid because the one we have leaks fuel just a little. Again, thanks for your help guys.
 

oldcatamount

Lieutenant Commander
Joined
Apr 4, 2010
Messages
1,740
Re: To all the boat motor experts, PLEASE HELP!!!

If it was a jet prop problem, it would over rev, not bog down. Sounds to me like a carb issue as well as the choke solenoid. A carb re-build and thorough cleaning along with new plugs and fresh fuel would be my suggestion. What makes you say the timing may be off?
 

Tommy12

Cadet
Joined
Mar 27, 2011
Messages
14
Re: To all the boat motor experts, PLEASE HELP!!!

I purrs like a kitten most of the time , but every once in a while it will jump. I also forgot to mention, we rebuilt the carb already. I read another post on here about the fuel tank not venting right. Could that be it?
 

oldcatamount

Lieutenant Commander
Joined
Apr 4, 2010
Messages
1,740
Re: To all the boat motor experts, PLEASE HELP!!!

It sure could be the fuel tank not venting right. When a motor of that size starts taking off, it's sucking some serious fuel and the tank vent needs to be wide open to allow air to enter the tank at the same rate as the fuel is leaving.
 

stylesabu

Master Chief Petty Officer
Joined
Aug 2, 2009
Messages
849
Re: To all the boat motor experts, PLEASE HELP!!!

propane enrichment easist way to tell if its a fuel problem.run a hose from handheld propane tank to air box assembly when it starts to stall open tank if rpm picks up start looking at fuel delivery, carbs and /or fuel pump
 
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