Won't rev past 1500 rpm in gear!?

[444]

Have an 82 175hp v6. Runs and revs fine in neutral but with a load on it won't do more than 1500 rpm. Tried putting on a spare prop (that I discovered has a slipping hub) and it will rev up fine in gear with that (slipping hub) prop but put on my good prop and once I give it a little throttle to get it up to 1200rpm in gear, anything past that will take me up to 1500 and no further. If I give it full throttle it sometimes wants to bog down or it will just sit at 1500 and lug me along at a few mph. Idles fine, starts fine, revs in neutral fine. I had a helper pump the fuel bulb while I was running it just to see if it was a fuel supply issue and that made no difference. No sputtering or missing, it just won't give me any rpm.

I'm thinking it may be an electrical issue? The previous owner said he put in all new electronics in it, and at least the stator has a CDIelectronics tag on it. I looked up the test info on cdi's website and the ohms for the stator low and hi check out okay but I don't have a dva for my multimeter. I'll check the resistance on the coils and trigger as well. Any other ideas where to check???

 

[86 century]

Re: Won't rev past 1500 rpm in gear!?

Start with the basics check comprestion those v6's will idle just fine with two cyl at 20 or 30 psi

While you are at it put the plugs back in the wires to check for spark.
Good luck

 

[444]

Re: Won't rev past 1500 rpm in gear!?

Yup, those are all the simple things I plan to check tomorrow morning. It's usually never something that simple though. I did a compression check on it before and all cylinders were around 120, but I'll do it again just to make sure nothing has gone wrong.

 

[sschefer]

Re: Won't rev past 1500 rpm in gear!?

120 is excellent compression for that motor. I would be looking at that stator replacement job the PO did. I'm not 100% sure on the 82's but on the 90' and up to 2001, you can mess up and get them 1 screw hole off. That causes a weak spark and you wouldn't really know it until you started having problems like you're having.

 

[444]

Re: Won't rev past 1500 rpm in gear!?

When I bought the boat, it came with a trashed lower unit, according to the previous owner it was running fine until the lower unit crapped out on him. He said he replaced the stator, trigger, power packs and rectifier and said the problem turned out to be a faulty fuel pump diaphragm. Like I said, I can tell at least the stator has been replaced for sure by the CDIelectronics tag on it.

How would I tell if the stator is one screw hole off? When I pull the flywheel, will it be will it be obvious how it can or should go in?

 

[j_martin]

Re: Won't rev past 1500 rpm in gear!?

I don't know why stator location (rotation) would make any difference. For ignition it supplies power to charge up the capacitors in a CD ignition system. Each of 2 tapped windings supplies one bank of cylinders.

Like others have said, a V6 can be made to idle on just a couple of cylinders, but won't have enough power to get out of it's own way. If someone's been "tinkering" with it, the idle speed has been set to compensate, and who knows what else is completely out of sync in the process.

If it's fuel related, then squeezing the primer bulb when it's balking should have an effect. If it's fuel pump or even restricted flow from filter, air leaks, etc, it should speed up. If the carbs are flooding, squeezing the bulb should kill it. If it has no effect, the problem is likely in the ignition.

Don't make the expensive mistake the PO made and throw expensive parts at it till the inexpensive bad part becomes obvious. Do the diagnostics before you buy anything. Spend a little money on the factory manual and a DVA. If you own this engine more than a coupla months, it'll pay back with interest.

 

[444]

Re: Won't rev past 1500 rpm in gear!?

All plugs are firing when cranking and rechecked compression and all cylinders are 120psi +/- 5psi. I'll try picking up a spark tester to see if I'm losing spark at higher rpms.

 

[444]

Re: Won't rev past 1500 rpm in gear!?

Threw my timing light on each cylinder while running it at just over 3000rpm in neutral and all cylinders were still sparking properly.

 

[Coloradolakeboy]

Re: Won't rev past 1500 rpm in gear!?

Did you take the boat to a higher elevation than the previous owner?

 

[444]

Re: Won't rev past 1500 rpm in gear!?

I'm 400-500' higher than the previous owner. That shouldn't make any difference.

I pulled apart the carbs and cleaned them out. They looked really clean inside to start with but I blew compressed air and made sure all the passages were clear. All of the floats needed their height adjusted. They were too low and they weren't even all set at the same height.

My middle carb is missing one of the float bowl vent tube jets and the bottom carb is missing both of them. What affect does this have?

Also I noticed the rubber hose that goes in/out of "C" on the engine block has rotted and fallen right off. What affect does this have on the engine? I'm heading out now to buy enough hose to replace all of it.

 

[CharlieB]

Re: Won't rev past 1500 rpm in gear!?

Unfortunately, testing for spark while rev'ing in Neutral won't tell you a thing.

Under LOAD and WOT much more air enters the cyl, which, once under compression, acts as an insulator in the spark plug gap, causing the ignition system to generate maximum voltage to arc across the elevated resistance.

Rev'ing in Neutral will NOT raise cyl pressure enough to cause sufficient load on the ignition for a reliable test.

Now if you had that same timing light rigged and tried to see spark while out on the water you might see a failure.

DVA testing is much easier to do, can be done cranking on the trailer, and is about THE most reliable indicator of ignition health.

 

[j_martin]

Re: Won't rev past 1500 rpm in gear!?

I'm 400-500' higher than the previous owner. That shouldn't make any difference.

I pulled apart the carbs and cleaned them out. They looked really clean inside to start with but I blew compressed air and made sure all the passages were clear. All of the floats needed their height adjusted. They were too low and they weren't even all set at the same height.

My middle carb is missing one of the float bowl vent tube jets and the bottom carb is missing both of them. What affect does this have?

Also I noticed the rubber hose that goes in/out of "C" on the engine block has rotted and fallen right off. What affect does this have on the engine? I'm heading out now to buy enough hose to replace all of it.

Whether altitude makes a difference depends on what altitude. Never mind where it was, look up the carb jetting chart for your engine/carbs and check them out.

Low float level definitely will sicken the motor

Those 3 vent jets missing is normal on some setups.

Bad hoses can definitely fuddle the tune of the engine. The sleeper is if the pulse hose to the fuel pump is soft, it'll lower pressure and delivery significantly.

hope it helps
john

 

[444]

Re: Won't rev past 1500 rpm in gear!?

I replaced all the hoses on the engine, did a link and sync, replaced the spark plugs that came on the engine when I bought it. Revs nicely on the driveway and idles better than it did before.

I'm going to do a DVA test on it too. I have an Amprobe brand multimeter which has a peak function made for measuring and recording min/max voltages on a/c. Does this sound like the same thing as a dva adapter for a regular multimeter?

Manual for it: http://amprobe.com/manuals/33XRA.pdf

 

[444]

Re: Won't rev past 1500 rpm in gear!?

I put the boat back in the water and the problem seems to have cleared up. I had cleaned out the carbs and set the float height, did a link and sync, new spark plugs and replaced the reed valve bleeder hoses.