66 merc 650 taking sweet time to get to max RPM

Took the boat out yesterday, and came upon a couple more problems before the starter kicked the bucket (going to the rebuilder tomorrow).<br /> First problem was that at WOT, it would only rev up to about 3000 RPM for about 3-5 minutes. Then it would suddenly change tone, and go on up to 5000-5500 RPM, plane out and run great! It ran fine except for sucking air at the fuel line quick disconnect at the motor (a quick squeeze of the bulb now and then kept it going. I bypassed it today). But unless I shut the motor off or it died, it would idle down, then right back up to max RPM. But every time I shut it off or it died, it would run slow for several minutes afterward. <br /> Second, in the driveway on the muffs, after a cold start, all it takes is a quick twist of the key, and she fires right up. On the water, I have to use the cold start lever and the choke no matter how long it has been running. <br /> For the record, I've rebuilt carbs, fuel pump, magneto, water pump, and L/U. Compression check was 100 to 110 psi. New J4C plugs.<br /> I know I have some fine tuning to do, but I was wondering if anyone knew how to fix these problems, or if one or both are normal for this motor?<br /> This is my first boat, which was bought as a fixer-upper. And BOY,DOES IT NEED FIXED! It was really neglected for the past 2 years by the former owner. He wasn't very mechanically inclined. So this has been a crash course in boat repair for me. And if it weren't for iboat forums, I'd prolly be banging my head against the hull (repaired that too!) BTW, I also own a jet ski, but to me, it doesn't count as a boat.

Re: 66 merc 650 taking sweet time to get to max RPM

NOS I'd check the fuel system for water and leaking fuel lines. CHeck your lines from the tank to the engine and the lines running to your carbs. You should have a good firm ball. Did you clean the fuel lines when you did the carbs? Check to make sure you didn't miss one of the holes in the fuel pump diaphram when bolting it back together. That's a mistake I made a little while ago. Make sure the butterflies in each carb open at the same time. Do the Timing & Snyc for merc inlines posted by Clams in this forum.

Re: 66 merc 650 taking sweet time to get to max RPM

I finally got a salvage starter. I fixed the problem of sucking air into the fuel line. Then I did the timing and synch sequence (now that everything else is finally fixed ) All I can say, just from running it in the driveway in a 55 gal drum is "WOW!!!" If not for Clams' post, I'd never have known that the throttle tang was 15 deg off! No wonder the timing at idle was 20 BTDC! I still need to set the idle in somewhat cold lake water, but that should be a breeze now. Thanks go to Clams, and to Roger for reminding me to check the basics first. BTW Roger, the one thing I didn't understand was your statement about "Check to make sure you didn't miss one of the holes in the fuel pump diaphram when bolting it back together." Other than that, I'm ready to take her out this weekend.... even if it is Memorial Day Weekend. Which around here, is like Christmas Eve at Wal Mart! But hey! I'm getting antsy! Thanks Again!

Re: 66 merc 650 taking sweet time to get to max RPM

nos1013 Where in KS are you going?<br /><br />Perry? Melvern? Pomona? LaCygne? Somewhere else?

Re: 66 merc 650 taking sweet time to get to max RPM

Farther south. Cheney, El Dorado, etc

Re: 66 merc 650 taking sweet time to get to max RPM

I was at Perry this last weekend <br /><br />Lots of wind .. lake was rough and I had to trailer it up (on plane was beating us up, going slow and we were taking waves over the bow). Too dangerous. The others were disappointed, but I wasn't taking the chance of swamping..<br /><br />16' Bayliner Capri

Re: 66 merc 650 taking sweet time to get to max RPM

Update: She now starts right up, idles fine, hole shots fine, but she's still planing out after 3-5 minutes of only running about 3000 rpm and going about 15 mph. Also, with a passenger, she won't ever plane out. The timing and carbs were double checked. It's running on all 4 cylinders, the carbs aren't running lean, nor rich. It's like there's a governor on it or something. Would the wrong pitch on the prop slow it down that much? It currently has a 19 inch pitch on an 18 ft 1970's tri hull. <br /> <br /><br /> Rob, Yeah, we spent all of an hour at a small lake west of Wichita on Sat. Even though it's only 250 acres, it still had white caps! The only time the boat did plane out was when it was going with the wind. Got to test out the bilge pump, too

Re: 66 merc 650 taking sweet time to get to max RPM

Anyone know why an outboard might run at half speed for 3 to 5 minutes, then suddenly take off and hit max RPM? I've done the timing and synch. Rebuilt the carbs and the magneto. It's hitting on all cylinders. I'm stumped.

Re: 66 merc 650 taking sweet time to get to max RPM

I'd say fuel starvation and it could be anywhere. Why don't you do a decarb first then go from there. Give it time to work; by that I mean it will start to loosen up any goo in your system, but it may take time to get it all. A sticking float valve in a carb might take awhile as would crud in a carb jet....even though you double checked them.<br /><br />Other thing you might do, just to know, is to check the squeeze bulb for firmness when it's lugging. If soft, fuel pump problem even though you just redid it. <br /><br />Mark

Re: 66 merc 650 taking sweet time to get to max RPM

Ok, here's a possibility. The Seloc manual shows 2 fuel pumps, oldmercs says to order 2 kits, but this motor only has one pump. There's a blockoff plate over the place for the second fuel pump. Could this be the problem?<br /> I opened the fuel pump today. It all looked just fine to me. Although the bulb isn't very firm. I'm thinking that might be because it's a Murray instead of a Mercury. Guess I'll go to the Merc dealer this week and pick one up. I'll look for some Sea Foam or Deep Creep this week, also.

Re: 66 merc 650 taking sweet time to get to max RPM

I have heard complaints on here about after market bulbs.<br /><br />You just answered your question. If the fuel supply was proper, and the pump was pumping properly, the bulb should be full of fuel when you are running.<br /><br />Now whether you need 2 fuel pumps or not, ask yourself this question.....what has been supplying fuel to this engine for it's prior life? One fuel pump?<br /><br />Mark

Re: 66 merc 650 taking sweet time to get to max RPM

That's a good question, and all I can answer is "I don't know". But I went to the marine salvage today, and picked up 2 fuel pumps and gobs of fuel lines for $5. So I guess I'll see about replumbing the fuel system tonight and tomorrow evening. I also bought a Merc disconnect and bulb today, as well as Sea Foam and Deep Creep. Guess I better get to work now!

Re: 66 merc 650 taking sweet time to get to max RPM

Like I said man, You lasted how many years on one fuel pump and now you need two????????<br /><br />Mark

Re: 66 merc 650 taking sweet time to get to max RPM

I just bought this boat in Feb, so I really dont know if it's always had just one fuel pump, or if someone cut some corners at one point during a rebuild.

Re: 66 merc 650 taking sweet time to get to max RPM

Update time: I havent changed to a 2 pump system yet, and I may not. Anyways, after 2 people told me that it was smoking too much, I decided to set the float lower. It's supposed to be set at 13/32" (.406) from the top + or - 1/64 inch. I reset it to 27/64 (.421) from the top, thereby lowering the float. I also screwed the idle mixture screws in to where the motor almost died, and only backed them off 1/16 turn. The holeshot sucks, but it planes out and runs up to 4000 RPM now, even with my 2 kids on board. Course, it still takes a while to get there. I'm thinking the float needs set another 1/64 inch lower so I can enrichen the idle mixture to improve the holeshot. I'm also thinking the 19" pitch is too much for the boat/motor combo, since max RPM is supposed to be 5000-5500 RPM. I was thinking about asking the marine salvage guy if he has a 15" or 17" pitch prop I could try. I'm honestly trying to learn all of this, but sometimes, it goes against what I learned with car motors, so I can be somewhat bullheaded about it. For that, I apologise. And thanks for the help so far!

Re: 66 merc 650 taking sweet time to get to max RPM

BTW, I only added a tach in the past week. So my previous posts were only estimates. I'm really sorry I was so far off on my estimates. I do appreciate all and any input! I wish to improve the performance of my old Merc. Keep her going, and pass on what I learn.

Re: 66 merc 650 taking sweet time to get to max RPM

Ok, so now you have possibly indicated that the engine has been overloaded which translates to carbon buildup to me and time to use your Sea Foam treatment.<br /><br />But you still have me puzzled. When something happens suddenly and drastically, something broke. Your replies haven't touched upon anything that you found "broken".<br /><br />On loading the engine, I have read on here where towers don't like to be lugged; like they just cave in.....but that should come on gradually, not all of a sudden.<br /><br />One more thought. I had an inboard tank once and put some moisture absorber in it. Was running across the lake one day at WOT, everything fine and bam, the engine died and I couldn't get it started. In short, the water combined with the trapper (alcohol?) in the treatment and made this wad of goo that worked it's way all the way to the fuel inlet connector at the engine and that stopped me.<br /><br />Also I read on here this am about a high speed stator going out on a guy?????<br /><br />HTH<br /><br />Mark

Re: 66 merc 650 taking sweet time to get to max RPM

Yeah, I put half a can of Deep Creep thru the carbs Friday evening on the muffs. And stuck a can of Sea Foam in the port gas can, which is what I ran off of yesterday.<br /> As far as anything being broken, I think I've found everything that was broken *knock on wood*.<br /> The whole fuel system is either new or rebuilt, except for the reeds.<br /> And once the boat planes out, it runs constant.<br /><br /> Anyway, after discussing this with a buddy of mine, I decided to lower the floats another 1/64" and richen the idle mixture screws. If it doesn't hit 5000 RPM after that, I'll be in the market for a 15 or 17 inch pitch prop. The guy that owns the marine salvage close by is really cool, so if he has both pitches, he'll prolly let me try em out before I buy. Course, he's an OMC guy, so he thinks it's great that I'm lowering his supply of Merc parts.

Re: 66 merc 650 taking sweet time to get to max RPM

Hey Nos, re-read your initial posting and you may be onto something in dropping pitch on your prop. Great that you can get to try em before you buy em.<br /><br />Be sure and insure that when you remove your prop the thrust washer remains on the shaft...at the front of the prop....grease up the splines, and torque the nut to 55 ft-lbs and lock your prop nut retainer tabs down (only 3 at a time will lock).<br /><br />Then spin the prop and insure that it spins freely before powering up. (Saying all this as I just noticed that this is your first boat.)<br /><br />Mark<br /><br />Mark

Re: 66 merc 650 taking sweet time to get to max RPM

Ok, thanks for the tips. But it's going to be a while before I get the chance to try out different props. It looks like the next 2 weekends are "jet ski weekends". I also have a Sea Doo, and family members are bugging me to let the boat (and me) rest, and go have a few thrill rides. I'll keep ya posted on the Merc. <br /><br /> Thanks again for helping me get this far!