Classic 50 just wont go

I purchased a 22ft poontoon boat with a 87 classic 50 45hp, I have gone thru the carbs and cleaned up the engine no leaks now. I put the motor down in a 55 gal drum it starts up fine and idles revs up so I Put it in gear in the drum give full throttle sounds good revs up good!<br />I then take it to launch ramp we get on it try to go up river and the motor does not want to rev up and we go about 5-10mph thats it. My questions are:<br />1. Is that to small of a motor for that size boat? to get going?<br />2. Could the prop be to steep and not letting it rev with it in the water? <br />3. If the motors big enough for the boat how fast should it get going ruffly?<br /><br />Or is the timing off or any other suggestions?<br /><br />Thanks<br /><br />Rick

Re: Classic 50 just wont go

Hey Rick<br /><br />What size (Pitch) prop do you have on there now? You should do around 15 MPH with that motor. Do you know what RPM's you are running at wide open throttle? These are need to know things before we can help much. I would say you should be running the 121/2" X 8" pitch on that toon...

Re: Classic 50 just wont go

Reving it up in the drum, unfortunately, doesn't tell you much unless you have really experienced how these engines run in different states of failure. For example, it will sound almost fine when these engines are running on only 2 of 4 cylinders. Since there is no or little resistance (engine in neutral or from exhaust air mixed in water in drum), they will rev right up and zoom past redline. <br /><br />The merc classic 45/50hp engine depending on which year in the 80s is a great engine. I am the original owner of a 1985 50hp. <br /><br />My engine spent part of its life on a 20' pontoon. It would run 15 - 20 mph depending on load and conditions. <br /><br />1) Check for spark on all cylinders<br />2) Check to make sure it is getting fuel through both carbs<br />3) Check compression if none of the above. <br /><br />1 and 2 are quick and easy checks. It is possible that you have the wrong prop, but your symptoms sound like a little more. <br /><br />Common problems in this engine include:<br />- Power packs start to fail and engine runs on less than 4 cylinders. Test for spark on all cylinders. You can pick up a cheap test light at any auto parts store (place it next to the spark plug wire while the engine is running). <br /><br />- Like any engine of this age, the carbs get gunked up over time and can use a rebuild. After a rebuild or a thorough cleaning, I have had the float stick on one of the carbs resulting in fuel flowing through only one carb. Again, the engine will miss on 2 cylinders. You can easily see this by looking down the throat of the carbs while quickly manually advancing the throttle (you should see droplets of fuel coming out of the stem in the throat). If this is the condition, you don't want to run the engine too long because it is not getting a fuel/oil mixture to parts of the engine.

Re: Classic 50 just wont go

I have checked all cylinders for compression all are good around 120pds<br /><br />I have check all cylinders for spark all is good very strong spark.<br /><br />Installed new plugs<br /><br />Took carbs apart and cleaned adjusted the floats as it was spitting out of the bowl vent made sure it was getting full throttle. <br /><br />I dont know how to tell what siz /pitch prop i have on it. How do you do that there is some numbers on it i can barely read though!<br /><br />Revs up good in drum of water.<br /><br />I have alot of exper. with 2 strokes as I build motorcyles and quads alot( from gas to nitro) so my jetting and spark and tuning are pretty good just stuck on why it will not go so im assuming to much wieght vs /motor vs / pitch of prop!!<br /><br />Any more help is appreciated?<br /><br />Thanks<br />Rick

Re: Classic 50 just wont go

If everything is good and you think you have a prop pitch situation, go to the iboats prop forum. there are people there that can help with set up and pitch. There are excellent advisers in all these forums.

Re: Classic 50 just wont go

The prop will have a part number, size and pitch stamped on the hub. <br /><br />All of your trouble shooting so far seems good. <br /><br />One option would be to take your prop off and take to a local marina or prop shop. You can compare it against others and get an idea. You may want to just try a lower pitched prop (aluminum props are reasonable). Just watch the engine rpms. Don't over rev the engine. <br /><br />What does your pontoon weigh?<br /><br />Was this engine on another boat previously? If so, how did it run on that boat?

Re: Classic 50 just wont go

search Clams "linc n sinc' since you rebuilt the carbs.

Re: Classic 50 just wont go

OK 15TH TRY, I purchased a 8' prop and it made very little if any difference at all. But what I did notice is like when you put the boat in reverse its like not engagin all the way it cluncks a little and like the prop is slipping because it does not go very fast in reverse if at all. If i sit back by the motor and the driver raises the motor up until it starts cavitating it will get rpms or our of the water with no resistance it gets rpms. But the boat will only go like 5mph is there something in the bottom end that could be causing slippage or major friction from letting the motor turn rpms in the water??<br /><br />PLease any ideas will be tried....<br /><br />Thanks<br />Rick

Re: Classic 50 just wont go

Originally posted by fishingdan:<br /> The prop will have a part number, size and pitch stamped on the hub. <br /><br />All of your trouble shooting so far seems good. <br /><br />One option would be to take your prop off and take to a local marina or prop shop. You can compare it against others and get an idea. You may want to just try a lower pitched prop (aluminum props are reasonable). Just watch the engine rpms. Don't over rev the engine. <br /><br /><br />I have no idea what the boat wieghts? It had this motor since we got it bought thru lean sale so cant talk to the previous owner!<br />Thanks<br /><br />What does your pontoon weigh?<br /><br />Was this engine on another boat previously? If so, how did it run on that boat?

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Re: Classic 50 just wont go

tbrracer,<br /><br />I feel for you. These things can be frustrating. <br /><br />I must say that the symptoms still lead me to believe that you are only running on 2 of 4 cylinders. <br /><br />Tilting the motor up until the prop breaks free of the surface greatly reduces back pressure on the engine and it will rev high quickly even with 2 cylinders (as it also would in neutral). As you know, it could easily blow right past redline and have a major failure. <br /><br />Since you have ruled out compression and spark, I would look at the fuel system. I would confirm that both carbs are actually feeding fuel the engine. I mention this because twice after rebuilding my carbs on the 1985 merc 50 (same engine as yours), the needle valve or float or both on one of the carbs stuck and no fuel got through to the engine through that carb. The result was that the engine topped out at about 1900 rpm. <br /><br />Try the following:<br /><br />- Remove the cowling and the engine top cover thing<br />- Remove the front cowling support<br />- You should now have clear easy access to the front of the carbs<br />- With the engine in the water or on muffs, start the engine up and look into the carb throats. Get a small flashlight if necessary. <br />- Carefully (i.e. keep you fingers out of the way of the flywheel) put your fingers on the throttle linkage on the top of the top carb.<br />- Quickly and briefly advance the throttle while looking into the throat of each carb. Do it while looking at the top carb and then do it again while looking at the bottom carb. <br />- As you advance the throttle, you should see droplets of fuel exiting the little stem (that is sticking up right in the middle of the carb float behind the butterfly) as it gets into the airflow and pushed into the engine. <br /><br />It is worth a shot.<br /><br />Dan

Re: Classic 50 just wont go

I will try that with the carbs again this weekend and verify that all cylinders are running.<br />I guess one at a time pull off the spark plug wires and see if its running on the other cylinders 1 at a time. Thanks alot for yout help I will let you know monday what happen.<br /><br />Thanks<br />Rick