73' 650 Merc Problems

Goin Broke

Recruit
Joined
Jul 30, 2012
Messages
5
Hello,
I bought 20 foot sweetwater pontoon about 5 months ago with a blown motor. I ended up buying a 1973 65 hp Merc. I put it on and it ran alright. After about 3 weekends of fun the battery died on me. I took it in for service and come to find out the starter went bad on it at the same time. To sum the story up, They changed the starter and i had them do a carb rebuilt kit because i had fuel coming out of the front of the carbs. I picked the boat up had the same exact problem so i took it right back to them. After that was all said and done the motor ran like a champ! After 1 full day of being on the lake the boat started to loose power. Using a GPS on my phone the boat would do 18 mph and after a long day maybe 8-10...? I have also had the boat stall (once) while at low idle. I disconnect the fuel line get it to fire and have to wait for the fuel to burn off so it will idle back up. I am lost to wha this could be and why am i having this problem after a carb rebuild kit? It did have some fuel coming out before but never lost power like it is now. I had them look at it today and the tech said sounds like it is running good to me. I know it is not right because it ran stronger before. Thanks in advanced!
 

kazek

Petty Officer 2nd Class
Joined
May 14, 2011
Messages
177
Re: 73' 650 Merc Problems

hi.i would pin point the problem...if its gas related or ignition coil overheating.do fuel test first.take the boat to lake and have your friend pump the priming bulb when it looses the power(idea here is to check fuel plow to carbs bowl)if it picks up power its fuel related and we will take it from there.you could use the choke to do that with similar results
 

Goin Broke

Recruit
Joined
Jul 30, 2012
Messages
5
Re: 73' 650 Merc Problems

hi.i would pin point the problem...if its gas related or ignition coil overheating.do fuel test first.take the boat to lake and have your friend pump the priming bulb when it looses the power(idea here is to check fuel plow to carbs bowl)if it picks up power its fuel related and we will take it from there.you could use the choke to do that with similar results

I did this once before and had no result from it. I also changed the primer ball today because it was old. Another hint that i found was, when i changed the spark plugs i found that were wet but a golden brown. I know the color is good but not being wet...? After talking it over with a couple of techy people i truly believe it to be running to rich. I think that over time the carbs are loading up with fuel and robbing power. Would this make since? Thinking about two options, Changing the plugs to a CJ8 (hotter burning plug) or tweaking the carb screws. Would this be a place to start?
 

oldman570

Lieutenant Commander
Joined
Mar 25, 2011
Messages
1,615
Re: 73' 650 Merc Problems

The plugs should be a darker brown and wet when pulled after the motor has been run. Sounds as tho the carbs are set to run to lean on fuel causing the motor to run to hot. Is the tell tail water getting real hot to the touch when the motor starts to lose power?
Oldman570
 

Goin Broke

Recruit
Joined
Jul 30, 2012
Messages
5
Re: 73' 650 Merc Problems

Ok, I take that color back. They are a darker brown. As for the water i have not touched it when running but after running it for a bit and back to an idle it is warm, not hot. I can try to run it and find out. I will see if i can get out on it tomorrow. How do you figure lean over rich?
 

oldman570

Lieutenant Commander
Joined
Mar 25, 2011
Messages
1,615
Re: 73' 650 Merc Problems

If the plugs are the darker brown the fuel mixture is probly fine. You will need to be sure that the carbs are opening all the way, and this can be done without the motor running. Just put the control at WOT and see if you can move the carb cam link a bunch. If the cam stop and control lever is set correct the cam should only move about a 1/8" . There should be a small screw on the dist. on the motor side that is the secondbary throtal pickup adjuster. Some are on a plastic plate and will brake off after age and use. That may be causing your trouble and not opening the carb all the way. A complet Lync and sync of the carbs may be inorder as the carbs they were rebuilt and should be done or checked to get everything set correct for the carbs and timming.
Oldman570
 

Goin Broke

Recruit
Joined
Jul 30, 2012
Messages
5
Re: 73' 650 Merc Problems

Update, took the boat out and observed the motor and carbs. Come to find out the bottom carb was not opening. Rather than pulling it apart myself i called the dealer that did the carb work and they said to bring it in. They tore it apart and come to find out it was mising the screw that linked the two carbs. It is all fixed now and running great. The mechanic said he was impressed that the motor ran that well with only one carb. Thanks for all the insight guys!
 
Top