86 MCM 170 Carb?

beckerdg

Petty Officer 2nd Class
Joined
Sep 9, 2002
Messages
147
Last weekend going fishing I started up at the dock and warmed up and idled out fine. Went to throttle up and the boat bogged down. Could not get the boat going on plane. After a couple minutes it started running a bit rough going from bogged down to pretty much full power. A couple minutes more and I had full power. Boat ran normal the rest of the day. I was kind of thinking maybe a little water in the gas?<br /><br />Went out this weekend and same problem only worse. Motor bogged down, check distributor cap for moisture, it was clean. Checked carb for extra fuel dumping from fuel pump in case the primary diaphram had broken, none. But the throat of the carb was very wet with gas. More than I would expect is normal. Took a look in the carb under power and one of the barrels looked to be dumping gas not really atomizing it.<br /><br />So desperate to fish I decided stupidly to idle out the few miles to the reef because it was running smooth just could not get full power. Well we spotted some birds working on the way and went over there to cast a bit (slowly) and stalled. Could not get started up because the engine seemed flooded. Pulled a plug on #1 cylinder and it was dry and looked normal.<br /><br />So we floated around a bit to let it sit and 15 minutes later I got the engine started. Now that we scared ourself we headed back. 5 minutes into the trip back the engine started cutting in full power then smoothed out. Ran in the couple miles on plane full power running like a top. Ran around the dock a bit no problems but now chose not to fish until I resolve the issue.<br /><br />Could the problem be as simple as a stuck float, or do I need to rebuild the carb, or is it something else? The boat has been running great all spring and summer.
 

BRIAN03

Petty Officer 1st Class
Joined
Oct 17, 2003
Messages
284
Re: 86 MCM 170 Carb?

Other than the simple things. If you have tried every thing else. Check the compression. If this engine has never been rebuilt or has back fired it will jump cam to crank timing. The chain streaches or the idler doesnt work. If you had 150 psi on each cylinder with a good battery. Now you check the compression and its 125 psi on all cylinders you have jumped timing. This engine has a chain tensioner.It will change about 25 psi of compression either up or down usally down 25 psi. If this is the case you need to pull the front cover and look at the timing dots on the pulleys. You will need a chain and tensioner. Pulleys are fine.
 

rodbolt

Supreme Mariner
Joined
Sep 1, 2003
Messages
20,066
Re: 86 MCM 170 Carb?

hello<br /> if it will run intermittantly at full power its fuel or ignition.<br /> if all else checks out its time to check elsewhere<br /> sometimes the tiny little plare that the breaker cam mounts on will have an intermittent ground fault. as in there will be no ground. its difficult to find but easy to fix. to test it stip a length of wire on one end. remove the dist cap. replace the cap with the stripped wire pinched between the plate and the cap. ground the other end to a clean ground or the negative battery terminal.if it runs better you found it if it does noit you just eliminated one spot.while the engine was stalled and would not restart did the tach needle move when cranking?if it made full power leave the mecanical parts alone. the reciprocating and rotating parts are fine. both carb venturies should have looked identical. you may have clogged main gets or some water in the fuel bowl.<br /> good luck and keep posting
 
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