74 650EL cuts out at full throttle

Hello everone. I am new to boating but have some basic knowledge about outboard motors. I am trying to figure out why my 650 3 cyl. is cutting out at full throttle. Had replaced some fuel lines to carb and cleaned and rebuilt carbs. Checked filter mesh for debris. New fuel line and bulb and 6 gal tank. Idles great in water and out with the muffs on the garden hose. Sputters on throttle. I am thinking about the fuel pump needing rebuild kit. Also wondering about a broken aluminum cowl bracket that has as mesh ground wire mounted on the top and bottom. Could this cause some electrical short. Bracket mounts at the rear of motor over and around the spark plugs. What type of fuel should I be using in this older motor? I have read not to use cheap fuel with added ethanol or a high octane fuel. Not sure what to use. Any advice is greatly appreciated. ANyone else with this or similar motor around? Feel free to PM.

Re: 74 650EL cuts out at full throttle

Sounds like a fuel pump rebuild is in order. Use regular unleaded gasoline and mix at 50::1 ratio with any TCW motor oil.

You might try pumping the primer bulb as you go to WOT. If that fixes it, it is very likely fuel pump.

Re: 74 650EL cuts out at full throttle

Thanks for the tip. Fuel pump rebuild sounds like a cheap option and good to know fuel pump is good then. Now just to find the parts.

Re: 74 650EL cuts out at full throttle

Did you open the vent on the gas tank?

Re: 74 650EL cuts out at full throttle

Did you do a final setup of the idle jets. If you left them at the factory setting they're probably too rich and when you hit that last bit of throttle your flooding out.

I had that happen on a 4 cylinder 100 then I remembered I was still at 1-3/4. I turned the idle screws down to 1-1/2 then 1-1/4 and it fixed it.

Re: 74 650EL cuts out at full throttle

Idle jet settings have no influence on high speed operation. Once the motor revs past 1500 RPM or so, the idle jets are no longer providing any significant fuel or air charge.

Re: 74 650EL cuts out at full throttle

I have opened the vent on the fuel tank all the way. Tip is appreciated though. As for the fine tuning on the carbs, I haven't had the boat in the water long enough to troubleshoot. Just enough to have a check on some of the work I have had done by a marine mechanic. I don't know why he did not take it for a run before saying it was good to go. Pee'd at that. Anyway, Just changed the lower end gear oil and in process of taking off the fuel pump for a rebuild. I'll keep you guys posted as I get the work completed. May take some time over the Canadian winter. Cold Eh! Thanks again All for your replies.

Re: 74 650EL cuts out at full throttle

Hole shot bogging is normally a sign of needing to richen the idle jets. High speed cut out would signal a different problem, yet it still could be a carb issue and/or fuel delivery. If you haven't had the boat out on the water, was the motor cutting out, before you took it to the mechanic?
As for fuel I would run 89 octane as a minimun, stay away from 87.
As for the bracket, it sounds like there is a ground strap attached to it, perhaps a picture would help.
Yep its getting a bit cool for boating up here, where abouts in Ontario do you hail from, (northern ontario here).

Re: 74 650EL cuts out at full throttle

littlelaker said:

I have opened the vent on the fuel tank all the way. Tip is appreciated though.

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I had the same problem, even with the vent open. The cap was rusty underneath and the vent holes were plugged. When I ran the motor with the cap loosened, it ran fine. I ended up drilling a 1/16" hole close to the center vent hole (where it screws into), on the underside of the bayonett only. Not through the top of the cap.

Re: 74 650EL cuts out at full throttle

Chris1956 said:

Idle jet settings have no influence on high speed operation. Once the motor revs past 1500 RPM or so, the idle jets are no longer providing any significant fuel or air charge.

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I agree it does sound improbable. I shouldn't have made the comparison to mine since it's a 2+2 with WME's that have separate factory pre-set air mix and no idle needles on 3 and 4. These are really sensitive to any adjustments made to timing, fuel pressure, and idle circuits.

Re: 74 650EL cuts out at full throttle

Fuzzytbay said:

Hole shot bogging is normally a sign of needing to richen the idle jets. High speed cut out would signal a different problem, yet it still could be a carb issue and/or fuel delivery. If you haven't had the boat out on the water, was the motor cutting out, before you took it to the mechanic?
As for fuel I would run 89 octane as a minimun, stay away from 87.
As for the bracket, it sounds like there is a ground strap attached to it, perhaps a picture would help.
Yep its getting a bit cool for boating up here, where abouts in Ontario do you hail from, (northern ontario here).

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Hey, I am From Southern Georgain Bay. Midland Area. Boating in Parry Sound, Dunchurch area.
Motor run OK before I took it out the third time and started fouling plugs. Yes sounds like you described the symptoms perfectly with "Hole shot bogging". The Boat was sitting for a couple of years before i picked it up. Figured Carbs were gummed up. So, I took it to a local marina and mech did a test to check if fuel leaked from the carbs by squeezing the bulb. When fuel poured out he said carbs needed cleaning and were not metering fuel properly. So I had him do the work. I was too busy trying to enjoy my holidays. Then boat sat for a few weeks before I could get in the water to try it out. Then ran like Crap. Soooooo.....
I took the Fuel pump off and found the Diaphram was caved in. Also braided fuel line in poor condition between pump and filter. Need to replace that too. Pump kit 6 bucks. As for the cowl bracket, Pop has an aluminum welder so he says he can weld it up for me. We'll see how it goes after that. Won't run it until spring now. Last weekend would have been perfect for a tour on the bay. Balmy for a couple of days here.

Re: 74 650EL cuts out at full throttle

Up near Thunder Bay here. I hear you on the end of season, I still want to get one last run in this year, but last weekend was too windy and I have to get wet to land n trailer the boat. Its at my camp (cottage to you southerners) and there is no boat launch. Winter should give you enough time to get it tuned up though, and then you will just need to fine tune it out on the water. Check out this post, it will help you out on the hows of linking n syncing. Which has to be done after a carb service.
http://forums.iboats.com/showthread.php?t=168855

Re: 74 650EL cuts out at full throttle

Thanks for the tip there on Link and sync. I think this here is a little more than i want to try myself. I will mention this term to a guy I know and see if he knows enough to help me out. Otherwise I will bring to local mech. Have you ever been to Horwood lake? Great Pikeral fishing.

Re: 74 650EL cuts out at full throttle

littlelaker said:

Thanks for the tip there on Link and sync. I think this here is a little more than i want to try myself. .

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It is easier than you might think. Just need a couple of tools thats all.

littlelaker said:

I will mention this term to a guy I know and see if he knows enough to help me out. Otherwise I will bring to local mech. .

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Any shop merc mechanic, in his 50's should know how to do it.

littlelaker said:

Have you ever been to Horwood lake? Great Pikeral fishing.

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Up here? Never heard of Horwood, there is one called Hazelwood though
which has good pickeral fishing.