60hp mercury won't run full throttle

[huggyb1972]

Ahoy all,

Our motor will not run out correctly above half throttle we believe the new style plastic floats may be to blame. The fuel pump is new all the hoses are new as well as one of the tanks. We can get the motor to full power by squeezing the primer bulb while underway.

Is there a way to adjust the plastic floats?

Dad and I bought a 60hp Merc this winter to replace our 45 Chrysler. This motor was bought in unknown condition and produced 120-125lbs of compression across all three cylinders. We replaced the stator and trigger because of wire insulation breakdown. The switch box and water pump is new.

The carbs were reworked after the compression check came back positive. Dad used sierra parts and he replaced the floats with new. We took the boat out for the first time last week and it didn't idle real well but would idle. We came out of the idle zone easy on the throttle and were impressed by the power difference. Then it started losing power after going wide open. We limped in to the trailer stopped by picked up fuel pump kit and took it back out and the idle was perfect. The diaphragm was leaking into engine we also found out our engine is a 85 by serial number, but newer like 87+ by powerhead evidenced by the 4 screw style fuel pump.

I am now wondering about the floats. They are plastic and from what dad has told me didn't appear to have adjustment. He also tossed the old style so we can't try them in comparison. Like I said I can squeeze the primer bulb and keep the engine running hard at full throttle but as soon as I lay off extra help to the fuel pump it loses power. This is a 3 seat fishing boat with with front seat stick steering.

 

[Texasmark]

Squeezing the bulb means that your fuel pump isn't pumping properly. Float adjustment is for sealing off the fuel supply at low rpms. At wide open throttle gravity has the float in it's lowest position, needle valve open the widest, and the least amount of fuel in the carb bowl.

Something is wrong. Wrong pump if new pump, wrong kit if doing an overhaul, or didn't get the check valves in properly, hole in diaphragm, and outside chance crack in fuel line or one not seated properly. To check for that shut the engine off. If the bulb gets hard and no fuel is leaking out anywhere go after the fuel pump.

If the bulb doesn't get hard, remove the connector from the engine and pump it again. If it gets hard bulb is ok. If not check valve leaking, out of place and may be blocking flow into engine.

Last check for foreign material in fuel feed line. Get a container and a wooden stick that fits in the end of the fuel line. Depress the check valve in the connector while pumping gas with the squeeze bulb. If anything but fuel comes out you have a deteriorated fuel line and particles from that are clogging your fuel passageways making it hard for a properly working fuel pump to suck an adequate amount of fuel.

Manual says that anything over 120 psi compression is AOK.

 

[huggyb1972]

Every single hose and the filter has been replaced. I'm going to spend some time on it tomorrow it would be great it there was something in the hoses or fittings, but I doubt it. Bulb gets hard. So how do you adjust plastic floats?

 

[Texasmark]

Every single hose and the filter has been replaced. I'm going to spend some time on it tomorrow it would be great it there was something in the hoses or fittings, but I doubt it. Bulb gets hard. So how do you adjust plastic floats?

My rule of thumb after many trips to manuals and using little doodads (gauges) that come in kits it this:

Put everything together except attaching the bowl. Turn the carb upside down and look at the centerline of the float...when made in 2 pieces that was easy....the seam where the top and bottom joined.

The centerline is parallel with the flange of the carburetor where the bowl attaches. If not, carefully bend the tab that presses against the needle valve without damaging the valve conical mating surface such that the two are parallel.

Reinstall the bowl and go.

While you have the bowls off, take some compressed air and blow around in the bottom of the bowl. Depends on the carb, but in my last ones (90 hp) the high speed jet is located in the bottom of the bowl and compressed air dislodged a piece of foreign material lodged in one of them....made a difference.

 

[huggyb1972]

We got the carbs off and sure enough they were to low. My manual here says 11/16" but I'm not certain how accurate that measurement is since the float material is different. I set them at the perscribed height ran the boat down to the water and it clicked off a 39mph pass across the water. The adjustment is in the metal transfer bar between the floats and the needle. It still seems like it may be starving a little but we're on the right track repair wise.

This old boat with the Chrysler 45 was a 23 m.p.h. boat before so 39 is like warp speed.

 

[Texasmark]

We got the carbs off and sure enough they were to low. My manual here says 11/16" but I'm not certain how accurate that measurement is since the float material is different. I set them at the perscribed height ran the boat down to the water and it clicked off a 39mph pass across the water. The adjustment is in the metal transfer bar between the floats and the needle. It still seems like it may be starving a little but we're on the right track repair wise.

This old boat with the Chrysler 45 was a 23 m.p.h. boat before so 39 is like warp speed.

My first family boat was a new 1971 16' Chrysler Sports Fury trihull with a 45. Waste of time trying to do any skiing. Took it back to the dealer and in taking a beating on the swap, swapped for a new 85. Night and day. Still rode rough being a light boat and shallow tri-hull. Next year (1972) In taking another beating bought a new 18' Caravelle quasi trihedral hull with dead rise to the stern; heavy boat, 125 Johnson....sweet boat. It's not about the money you don't have being a young couple with 4 kids and all........it's what you get for what you spend is what stays with you.....the money is gone was my lesson. And now you know the rest of the story......"Paul Harvey" news caster.

 

[huggyb1972]

The boat is a Chrysler Basspro. We have a few boats between us. This is just our fish only boat we bought a 21' Bayliner cuddy last year that were redecking. The deck is in now we just need to get the furniture put back in and finished. Dad has his Searay 160 that he bought new in 89' and I have a Spectrum 1950 fish n ski.

 

[huggyb1972]

So today I pulled the carbs to see what was in the bowls and found 2 little black pieces in the bottom carb that came out with the main jet. Potential reason for the new problem. While going through the manual though I came across the jet sizes for my motor and according to Seloc's manual I'm jetted wrong I have a 72 & 78 in the main jets and 96's in the vent. Seloc lists 86 main and 66 vent. So to stay I'm cornfused would be and under statement.

 

[racerone]

Seloc manual ?-----Perhaps visit a Mercury dealer and get a second opinion on jet sizes.

 

[huggyb1972]

Seloc That's the name I believe. The jetting on the carbs is more like what would be on a 70hp. Is it possible that whoever changed the powerhead put a 70hp head on a 60hp lower? We pulled a plug and attempted to take a stroke measurement and it appears to be the 60hp stroke.

 

[racerone]

Any pictures of this motor.---60 and 70 hp may have the same stroke.

 

[huggyb1972]

Manual says 60 is 2.562 70 is 2.650. Picture is a no go the upload doesn't like the file size.

 

[Texasmark]

The little black things are pieces of deteriorated engine fuel lines and are probably the source of your problems; were mine. Not looking back over this post, if you redid all your lines, while your carbs are off and your carbs are now cleaned out, before you reassemble with the jets as they were/are, get something to catch the gas from the gas lines that go to the carbs and using your squeeze bulb, flush out the lines.

Then put it all back together and go out and try it again.

 

[huggyb1972]

Yeah I got ahold of the Merc dealer here in town and asked about the jets. The main jets are either supposed to be 72 and 74 with the 16a carbs and 72's with 13a carbs. I have no idea where the 78 came from. We'll run it down the lake again and see how it goes. I am getting really good at removing the carbs on this outboard now.

 

[Texasmark]

Yeah I got ahold of the Merc dealer here in town and asked about the jets. The main jets are either supposed to be 72 and 74 with the 16a carbs and 72's with 13a carbs. I have no idea where the 78 came from. We'll run it down the lake again and see how it goes. I am getting really good at removing the carbs on this outboard now.

If there is a nice thing to it, that's it; you've BTDT so the second and subsequent trips are "old hat". Keep us posted on the latest water test.

 

[huggyb1972]

We didn't change any carb jetting the last time out only went from a 13p to a 15p prop. The motor ran flawlessly full power no.problem. The 15p is to much prop for the boat in current tune it was only running 5k rpm at 39mph. With the 13p we were running 6k rpm at pretty much the same speed. We're splitting the difference at 14p and will see how it works.