mercruiser 260 help

[85_celebrity]

I have a 1985 Celebrity 190 BR with a mercruiser 260 Alpha 1 with a 350 chevy motor that I bought used this spring. I have gone through and done all the tune up stuff(plug, wires, cap, rotor, changed all the filters and set the timing per manual spec)When I bought the boat it was very well taken care of but as with any boat this old has a few little problems to address. Ever since the first time out with the boat it has been a bit slugish. The boat weighs 2650 dry and may have another 1000lbs of people and gear on it during normal use. When I say sluggish I mean it won't rev past 3000-3200 rpm no matter what I do. The boat had a new carb put on it about a month before I bought it but it will not come into adjustment not matter who messes with it and backfires occasionally when applying the throttle off of idle. Every time we put the boat in the water I have to take a little bit of fuel and fill the float bowls up with fuel because the are bone dry. The boat seems to run decent but I think that it should run a bit faster than 35mph and also should turn more than 3200 rpm. I have talked with other people with similar boats with the same engine outdrive combo and the are running in the 50+ mph range with more weight on board and running a 13x21 prop. That prop size seems a little small. The boat had a 15x19 prop on it when I bought it and have tried a 14x19 and picked up 200 rpm but no speed. I am looking for ideas that maybe causing the boat to be sluggish. I am also considering replacing the intake with an Edelbrock 2101 intake and either a 1409 or 1410 carb depending suggestions. I may also put a small marine cam in it and have the heads freshened up and gasket matched. I use the boat primarily for buzzing around the lake with the occasional fishing and tubing. Sorry if my first post is rambling and lengthy but the season is drawing to a close and I would like to save some pennies over the winter for repairs on the boat if need be. I cant seem to find any info on the MFG. of this boat because they have changed hands many times in the past few years. I would also love to find some interior pictures of the boat someplace so I can have the seats replace with the proper seats and not these crappy plastic based seats. I guess my questions are shouldn't it rev higher? Shouldn't the MPH be higher? Why do I have to fill the carb up with fuel before starting it after sitting for more than a day or so? What prop would be best suited for this boat. And, Are the mods I have planned going to make a seat of the pants difference. I am pretty convinced about changing the carb, doing away with the quadrajet and stepping up to either a holly or an edelbrock. Thanks in advance.

 

[scorpion230]

Re: mercruiser 260 help

First is it a Car 350 or is it a marine application?
Because yes there are some differences..
Performance wise the Merc350 has a cam designed to produce lower RPM torque.
As far as putting a Carb on there again you need to make sure that it is a marine application (the foats sit lower to prevent fludding) but edelbrock does make a good marine carb. Check summitracing.com to order.. free shipping and no taxes!!!
If in the end it doesnt help you can check to make sure your linkage is adjusted correctly

 

[85_celebrity]

Re: mercruiser 260 help

It is getting full throttle, flame arrestor is clean and free of obstruction, haven't checked fuel pressure yet, but don't think it's a pressure issue because it will rev well over 5k with thie muffs on and no load. Also is 260 the HP rating or just a series number?

 

[blh1972]

Re: mercruiser 260 help

260 is the HP rating.

 

[180shabah]

Re: mercruiser 260 help

but don't think it's a pressure issue because it will rev well over 5k with thie muffs on and no load.

Reving to 5k with no load doesn't mean anything.

Don't start shopping for carb, intake, cam etc until you know what is currently wrong.

Have you performed a compression test yet. You also need to verify that you are getting proper timing advance.

 

[imported_TheMan]

Re: mercruiser 260 help

Possibly the wrong gear ratio in drive?

 

[BuzzM]

Re: mercruiser 260 help

I have a 1983 Merc 260 ( 5.7 ) with a pre-alpha outdrive that suffered similar symptoms. After a long effort at figuring it out, it turned out to be a bad choke assembly. I replaced the bi-metal spring and cover and it ran great.
May not be relevant, but I also had a prop once that was starting to slip it's hub, that gave me fits. It just felt very sluggish, struggled to get on plane, especially with 4 passengers aboard. It would blow out occasionally, then it finally started slipping enough that it was obvious.
I changed the prop , and it was fixed.
Just a couple of thoughts.

 

[ziggy]

Re: mercruiser 260 help

here's the link to all merc. service manuals. yers is in there......which one i don't know....big files. so takes a bit of time + free space to down load them.

"http://www-alt.mercurymarine.com/mnetdata/sisdata/srvcovr.pdf"

there's many reasons ya may not reach wot. yers is certainly to low.
agree with hm, like usual. no load wot don't mean anything. + yer engine probably won't like that.....

a list from dons....

List of possible causes of low WOT.

Engine Won't Reach Operating RPM. Check

• Fuel condition. Type and Octane possibly old fuel
• Propeller pitch or diameter, damaged blades
• Restricted fuel pickup tube or anti siphon valve Fuel System Test
• Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
• Marine growth on hull and outdrive
• Wrong gear ratio in outdrive
• Restricted carburetor air intake (clogged flame arrestor)
• Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
• Poor cylinder compression Compression Test
• Carburetor defective, or wrong type.
• Fuel pump pressure and vacuum
• Boat overloaded, improperly loaded, or improperly trimmed.
• Engine Overheating
• Engine timing and ignition system operation (Full tuneup done recently)
• Remote control cables and linkage for proper travel to open throttle plates fully.

__________________
Don S. __________________

thanks don s. that sure is a helpful list.......

 

[85_celebrity]

Re: mercruiser 260 help

First is it a Car 350 or is it a marine application?

It is the original mercruiser engine that came with it in 85 I saw the merc tag rivited to the block the other day.

 

[85_celebrity]

Re: mercruiser 260 help

Have you performed a compression test yet. You also need to verify that you are getting proper timing advance.

Compression test was performed by a local marina that looked it over before i bought it. The wrote down what they were and the seemed good if it were a car and i was surprised at how close they were. Advance has been checked and checked and checked again. If I remember correctly it was 36* at full advance.

 

[85_celebrity]

Re: mercruiser 260 help

List of possible causes of low WOT.

Engine Won't Reach Operating RPM. Check

• Fuel condition. Type and Octane possibly old fuel
• Propeller pitch or diameter, damaged blades
• Restricted fuel pickup tube or anti siphon valve Fuel System Test
• Crankcase oil volume, high oil level can cause aerated oil and lifter collapse
• Marine growth on hull and outdrive
• Wrong gear ratio in outdrive
• Restricted carburetor air intake (clogged flame arrestor)
• Restricted exhaust system (broken exhaust shutters/flappers) in engine transom shield or drive
• Poor cylinder compression Compression Test
• Carburetor defective, or wrong type.
• Fuel pump pressure and vacuum
• Boat overloaded, improperly loaded, or improperly trimmed.
• Engine Overheating
• Engine timing and ignition system operation (Full tuneup done recently)
• Remote control cables and linkage for proper travel to open throttle plates fully.

__________________
Don S. __________________

thanks don s. that sure is a helpful list.......

Ok lets run down the list.

Have drained and filled with fresh gas once and ran 3 or 4 tanks through it and also tried dry gas.

Tried a 15x19 prop same results
tried 14X19 prop picked up 200 rpm and no mph

I have not done the fuel system test but I will this weekend.

No growth on hull boat it trailer and washed after each use

How do I check gear drive ratio?

Flame arrestor is clear and clean runs the same with it off.

I did see the flappers the other day when I had the piping apart to replace the upper bellows that go from 4" to 3" are they supposed to just flop around there?

Carb Defective or wrong type I am leaning very heavily towards this and the guy put it on himself and wasn't the most mechanically inclined person most of what he "fixed" I am have to go behind him and re-fix. Is the a number I should look for on the carb to tell me it it's a marine carb?

I dont think that 2 people would be over loaded with 3 ultralight poles and a small tackle box would be overloaded. I have tried in in just about every trim position and it does get better but it tops out a 3200 rpm

Checked temps with a raytek gun and also put on a new temp sender all is within spec runs at 150* max and that is after a long run towing a tube.

Ignition is working properly and timing has been checked and checked again.

Cables are opening throttle plates all the way.

Sorry if I come off as rude I am just so frusterated with this boat.

Also just a guess but what do you guys this this boat should run MPH wise?

 

[scorpion230]

Re: mercruiser 260 help

Ok lets run down the list.
How do I check gear drive ratio?

your gear ratio should be 1.5:1 if memory serves me correctly check either your Clymer service manual or you Selco manual pretty sure that they have it
but like I said almost certain that its 1.5:1

 

[180shabah]

Re: mercruiser 260 help

I didn't think you sounded rude.

If you have eliminated the spark side of the equation, then that leaves air and fuel. You said that you saw the flappers in the exhaust tube, however it is still possible that there is an old one lodged in the transom shield. The drive will need to be removed to check. This would also make it easier to check the drive ratio. Just count the rotations of the input shaft compared to a single rotation of the prop. should be 1.5:1

As for what carb should you have, it is irrelevent. It could have been changed once or twice in the last two decades, and as you pointed out it may or may not be marine. If you could post the manufacturer and model number of what you have someone here will be able to tell you if it is marine rated or not.

 

[Don S]

Re: mercruiser 260 help

Have drained and filled with fresh gas once and ran 3 or 4 tanks through it and also tried dry gas.

That cures the problem of the old gas, and water in the gas (Hopefully your new gas didn't have water in it) but it doesn't cure the problems with the tank itself. That is the reason for the fuel system test in item 3.

How do I check gear drive ratio?

Do all these steps in order.
1. Shut off the battery switch
2. Pull the spark plugs out of the engine.
3. Put the shifter in forward.
4. Turn the engine till the prop starts turning, continue turning till the timing mark is at TDC.
5. Put a mark on the prop hub and the drive housing that align with each other.
6. Turn the engine by hand while someone watches the marks on the prop, and count the revolutions the crankshaft makes to turn the prop 1 complete revolution.
7. If it took 1.5 revolutions of the crankshaft, then you have a drive ratio of 1.5:1 which is what is needed for a small block V8. (a 260).

 

[MikDee]

Re: mercruiser 260 help

Most of the Mercruiser V8's are 1.5X1 reduction ratio. As far as speed, you should be able to pull 4600rpm (recommended max, with at least a 21 pitch prop) 4600rpm divided by 1.5 = 3066rpm X 20"pitch (21 minus 1) = 61.33mph minus 10% slip = 55.19mph would be ballpark.

I had a 20' SeaRay bowrider that would do 50mph with a 228hp/305 chevy Mercruiser, and a 19" pitch prop at 4600rpm.

By the way, if your carb is losing fuel, it could have a leaky jet or a crack in the body causing leakdown, and rough running especially at idle.

 

[85_celebrity]

Re: mercruiser 260 help

Ok I was also just reminded by my wife that the carb having to be filled didn't start until I changed the fuel water seperator. Was i supposed to prime this filter by filling it with fuel before I put it on? Also thanks so much for all the help up to this point. I am off for the next three days and I am planning on spending some time with the boat.

 

[Haut Medoc]

Re: mercruiser 260 help

Ok I was also just reminded by my wife that the carb having to be filled didn't start until I changed the fuel water seperator. Was i supposed to prime this filter by filling it with fuel before I put it on? Also thanks so much for all the help up to this point. I am off for the next three days and I am planning on spending some time with the boat.

No you should not have to, if anything I'd pour a bit directly into the carb.......

 

[MikDee]

Re: mercruiser 260 help

You should check out your fuel line back from the fuel pump, all the way to the end of the fuel pickup in the fuel tank for debri, or a clogged filter, and or, a clogged, or defective antisiphon valve, these are common problems on used boats.

 

[85_celebrity]

Re: mercruiser 260 help

I am ignorant to where the anti-siphon hose is any info on this would appreciated.

 

[180shabah]

Re: mercruiser 260 help

Follow the fuel line from the filter back to the tank. The barbed fitting on the tank that the line is clamped to should have a spring and check ball inside it. This is the Anti Siphon valve.