mercruiser 260 no power

[IBILTIT]

I have a 1985 mercruiser 260 chevy v8 in a bja force 220 I purchased the motor as a used unit that was in good shape however after recieving the engine I was surprised to find that the motor was actualy a almost new engine that had very few hours if any on it and it apears to be a factory repower unit as upon close inspection none of the bolts or hardware have had the factory paint cracked off and looking into the valve covers the rockers and pushrods are still brand new looking and the oil I drained out also looked brand new. The only thing that doesnt look new is the distributor. After installing the motor with fresh oil ,oil filter, fresh fuel ,fuel filter both in the carb and the fuel water seperator, and cmplete flush of the fuel tank I took the boat out for a test the acceleration was poor at best and it will only reach a max rpm of 3600 at 30 mph the boat just wont get on plane I did check and the secondaries on the rochester 4 barrel are opening up as they should when you go to wot but it just wont go I have checked timing thats correct other than the lack of power the moter run seemingly well I put about 5hrs on it over the last weekend and it idled started well I have a 14.5x16 4blade prop.

 

[Haut Medoc]

Re: mercruiser 260 no power

Welcome to iboats.....
What condition are the ignition wires in?.......
Are they in the proper firing sequence?.......
How old are the exhaust risers/manifolds?......​

 

[Maclin]

Re: mercruiser 260 no power

I would check the ignition dwell and then do a compression check.

You did not mention what all was used from the original setup regarding electronic ignition control modules and the like. It could be that the distributor currently installed is not compatible with the original system. Then again the distributor that came with it may be a completely self contained unit with no external module. Perhaps wiring is not correct in this regard.

 

[Haut Medoc]

Re: mercruiser 260 no power

An '85 should be a TB IV, what type of ignition do you have?......
Points or electronic?.....​

 

[Limited-Time]

Re: mercruiser 260 no power

A quick compression check will indicate the engines relative condition. And rule out any major mech. issues.

 

[paulrfrancisco]

Re: mercruiser 260 no power

Does it rev up well in neutrual? Have you checked the mechanical advance in the distributer? They could be frozen.

 

[IBILTIT]

Re: mercruiser 260 no power

Thanks so much for the all of the fast replies
1 The firing order is correct
2 Wires are new
3 Cap and rotor are new
4 Electronic ignition
5 Free revs to 6000 rpms like normal
6 Exhaust manifolds and risers look new externally but could they be partialy blocked internaly ? I had a gut feeling and was suspect of this right away
7 How do I tell if the dist. is correct for the control box all wiring is in perfect condition and not cut, spliced or omited and apears to be connected to the proper termination points
8 Does the electronic ignition system have mechanical adv. I dont remember seeing any when I replaced the rotor

 

[Limited-Time]

Re: mercruiser 260 no power

Thanks so much for the all of the fast replies
1 The firing order is correct
2 Wires are new
3 Cap and rotor are new
4 Electronic ignition
5 Free revs to 6000 rpms like normal
6 Exhaust manifolds and risers look new externally but could they be partialy blocked internaly ? I had a gut feeling and was suspect of this right away
7 How do I tell if the dist. is correct for the control box all wiring is in perfect condition and not cut, spliced or omited and apears to be connected to the proper termination points
8 Does the electronic ignition system have mechanical adv. I dont remember seeing any when I replaced the rotor

1,2,3 Good
4, What type
5, Doesn't mean anything, a V8 with 2 dead holes will free rev. Additionally thats a good way to scatter your engine.
7,Disassemble and inspect, is the only way to tell.
8, Depends on the system

 

[reimelss]

Re: mercruiser 260 no power

I am having the same problem I just made a recent post. I have a 1986 Merc 260 Alpha 1. My boat Mechnaics says it could be something with my gear ratio.

 

[IBILTIT]

Re: mercruiser 260 no power

I will do a compression test tonight. I didnt hold 6000 for any period of time just cracked the throttle real fast. Is there a way to identify the dist type and the electronic control box to tell if they are properly matched. Any thoughts on the plugged exhaust I forgot to metion also that the port side ex. riser and pipe run about 25 -30 degrees f hotter than the starboard this was confirmed with a infrared temp sensor

 

[Limited-Time]

Re: mercruiser 260 no power

Do you know if the ing system is original to the boat? If so identifying it shouldn't be a problem. Just post the original engine SN and some one here will id the system. As for the difference in riser temp. I'm not sure about that. I know mine do not "feel" the same temp when running.........but they have been that way since the boat was new.

 

[Maclin]

Re: mercruiser 260 no power

The compression check will mean a lot. On that new of an engine the valve lash could be a little tight and being new to you if you did not build it then you may not have thought to check it. A compression test tells all!

I think the 20-30 degree difference in the riser temps is pretty normal on a V8. I can lean on mine for a few seconds while the engine is running and one will feel slightly warmer than the other but still not uncomfortable. What actual temps are you seeing from the gun though?

 

[Coors]

Re: mercruiser 260 no power

http://forums.iboats.com/showthread.php?t=167561

That always needs checking.

 

[IBILTIT]

Re: mercruiser 260 no power

did a compression test and all cylinders are at 130 +-2lbs also pulled exhaust risers and both sides are clear and look normal all the plugs look the same although there is not much on them to read if anything they look a little rich it has a tb IV ignition system and there is no mechanical advance the system does advance as rpms change (checked w/timing light and base timing is correct) also looked at another motor of same vintage and the componets of the ignition system were all the same I am going to try a new set of plugs tonight and then start to short out each cylinder till I have it running on 1 cylinder at a time and test each one and see what happens

 

[Limited-Time]

Re: mercruiser 260 no power

That ing system may require a special procedure (being put in base timing mode) in order to be set correctly. I'm not sure, but Dons, rodbolt,Bond-o, or one of the other guys in the know will let you know for sure.

 

[jerryjerry05]

Re: mercruiser 260 no power

Your riser temp prob is from not enough water on the muffs.It sounds like a fuel delivery prob. Check vent (mud daubers) Or twisted hose. Possible pickup tube clog at the anti-siphon valve.Jerry

 

[jerryjerry05]

Re: mercruiser 260 no power

Your riser temp prob is from not enough water on the muffs.Different temps in the water suggest a clogged riser.Your boat should go until it shuts down because of high temps.It sounds like a fuel delivery prob. Check vent (mud daubers) Or twisted hose. Possible pickup tube clog at the anti-siphon valve.Jerry

 

[rad1026]

Re: mercruiser 260 no power

TB IV does not need to be placed in base timing mode.

 

[IBILTIT]

Re: mercruiser 260 no power

lower unit has been removed pump replaced and mud dubbers removed no kinks in hose and anti siphon valve is clean and functioning I really appriciate all the comments and help so keep thinking sometimes you just need a new idea or point of view this all helps even though I still havent hit on it yet thanks again!!!!

 

[Haut Medoc]

Re: mercruiser 260 no power

That ing system may require a special procedure (being put in base timing mode) in order to be set correctly. I'm not sure, but Dons, rodbolt,Bond-o, or one of the other guys in the know will let you know for sure.

TB IV does not need to be put in base mode.....