bogs and surges at high speed

[vegard]

So, I took my 1970 sea ray with 1974 85 hp johnson out again today, only to find a new problem. Since last time out I changed the primer bulb, and cleaned all the fuel fittings.<br />Today I ran the boat for about two hours. It idled fine, but when I gave it gas, it was slow to respond, and when it was up on plane, I only got about 1/2 to 2/3 of the speed I got on my last trip. It also surged. Every now and then, it would boost up, and give the boat a little push then drop back down. What do you guys think? <br />My carbs are clean, the fuel pump is great. Im at a loss. I want to take care of this problem and head back out on sunday.

 

[Hopsdak]

Re: bogs and surges at high speed

Silly but, you never know.<br />Did you happen to check and make sure you installed the bulb in the right direction?<br /><br />I'd also take a look and make sure your fule lines are tight and your not getting any air in them. Sounds like it's starving for fuel at higher RPM.<br />--Hop

 

[vegard]

Re: bogs and surges at high speed

the bulb aint backward. Could it be anything but fuel starvation?

 

[ezeke]

Re: bogs and surges at high speed

Make sure your choke is working properly. If you have to, run the boat with the cover off the air silencer so that you can see what the choke is doing. <br /><br />Just blow out those jets on the bottom of the float bowls (behind the drain plugs)just to be sure. <br /><br />I can't think of anything else unless a coil is breaking down. You didn't change the wire on your coils did you?

 

[Forkin' Crazy]

Re: bogs and surges at high speed

If the bulb was backwards, it wouldn't pass any fuel through it at all (check valves).<br /><br />I agree, make sure the choke is working properly. It has springs that hold it open. The cylinoid may be gummed up where the plunger goes in and out. It should moved with your hand freely and the spring should open the blades back up.<br /><br />During the surge, momentarily activate the choke. If it speeds up, it is lean. Just because the fuel pump is pumping fuel, doesn't mean it is functioning properly. Check the fuel pressure at full throttle. I think it should be inbetween 2.5 and 6 psi.<br /><br />FC

 

[R.Johnson]

Re: bogs and surges at high speed

With an engine of this age, or any engine for that matter, go back to basic's. With the air cover off, use a squeeze bottle of gas to feed each carb. Ground the plug wires one at a time. Check the compression. You need fuel, spark, and compression. With an engine that age, I pull the cylinder heads as a matter of course. Take it one step at atime, and let us know what you find. The reason I pull the heads is that I have been fooled to many times with a compression guage.

 

[vegard]

Re: bogs and surges at high speed

Ive done all that stuff recently. I did the basics:<br />Strong spark<br />good compression<br />fuel pump and carb rebuild<br />reeds are good.<br /><br />I will try the choking trick, and I will change my fuel line (it looks suspect) Ill let you know what happens tomorrow when I put it on the water.<br />Thanks for all the replies, and keep sending ideas if ya got em!

 

[Walker]

Re: bogs and surges at high speed

Sounds like you may be dropping a coil under load. Clean all the coil ground straps real good. Also if you can, fire it up at night with the hood off and look for stray sparks from the coils. With some good insulated sparkplug wire pliers pull each wire off while running and watch for stray sparking.

 

[vegard]

Re: bogs and surges at high speed

Alright, after a day on the water... I nailed one problem, but I am left with a new one. I found that there was crud that had started clogging the fuel filter, and had gummed the carbs, so I rebuilt the carbs in the parking lot at the boat ramp and headed out again. Then I got full throttle and the boat ran probably twice as fast as before, but a new problem surfaced. As I give the boat more throttle, it works just fine up to about 1/2 to 2/3 throttle, where it bogs down and dies if I keep accelerating. But if I take it easy and gently (over like 15 seconds) let it speed up, letting off a little when it bogs down, it will pick up. And once it does, it runs perfect, and its not a problem until next time I let it all the way back down to idle. Any ideas on this one? <br />I think its a fuel problem again, because I tried spraying some premix in there when it bogged, and it took off.

 

[surphrat420]

Re: bogs and surges at high speed

I have a 1986 200 evinrude that was doing the exact same thing. It took a year for me to figure it out. Try this. disconect the timer base arm from the top of the throttle arm. this is the linkage that when you move the throttle lever forwards the timmer arm is spring loaded and will follow the throttle. on mine its just a small plastic ball that snaps in and out of place. then try to rotate the timer base back and forth with your hand, IT should be VERy smooth and VERY easy to move. If not then the porblem might be that. when you move the throttle forward the timming is getting stuck and not advancing for 10-15 seconds or until the vibration gets the spring moving. to fix this you have to remove the flywheel and the stator and the timer base and the greese EVERYthing down under there even the small plastic ring that sits under the timer base(i used a spray white lithium) then reasemble. This solved my problem no my boat takes off full throttle every time!! Good LUCK... let us know !<br /><br />PEACE AND WAKEBOARDING TO ALL

 

[vegard]

Re: bogs and surges at high speed

When I push the throttle, I see the timing arm move correctly, but I will further check out your suggestion on wednesday.<br />I am starting to wonder if its the float valve. Are there any adjustments to do to it? when I hold the carb body upside down, it looks parallel to the gasket surface. Is that the only check for the float valve?

 

[ezeke]

Re: bogs and surges at high speed

The float can be perfectly adjusted and you can still get a lot of problems in that area. <br /><br />For one, get a can of Permatex Spray-A-Gasket, NAPA # 765-1224 or similar product and make sure the gaskets are tight.<br /> <br />Secondly, the high speed fixed orifaces (57C)are very small openings (.057), are located at the very bottom of the float bowl, and are easily clogged.<br /><br />Finally, the float valve itself can easily stick.<br />The original assembly was part 378895 but see if you can find out from Joe Reeves if there is an upgrade. He is definitely the best source for this type of information.

 

[vegard]

Re: bogs and surges at high speed

The float is new, and the jets are clean. I am fairly convinced that its a fuel problem though. It really seems logical to me that the float valve would be causing this. I have determined that it is caused by a fuel deficiency.