Okay, I give!

I have a 88' Johnson GT150 that is giving me fits. It starts and idles great, almost to good for a Johnson! THe problem comes when I put it under a load it spits, sputters, then takes off, spits, sputters, then takes off, repeat and repeat, until you have ran it for 30 minutes or so. It will then take off with no problems and run like the wind, no hiccups at all.

I know the regulator/ rectifier is bad, and I am suspecting it is possibly shorting out one of the power packs? Does this sound feasible? I thought it was a fuel problem. I replaced all the fuel lines from tank to motor, new primer bulb, new fuel filter and it acts the same. I just bought this boat and know nothing about it, the owner knew very little and he had owned it 6 years.

Problem is replacing the regulator/ rectifer, power packs, thermostats, possibly the stator, and a few other things, I can buy a factory remanufactured motor for just a little more and get rid of this piece of poo.

Maybe I am just frustrated because it didn't do this when I bought it a month ago and now all the demons are coming out! I have also got to find a way to gently break it to my wife I need another 1k+ just to get us back on the water for the weekend!

She won't be as understanding as I am!!!

Re: Okay, I give!

bump...

Re: Okay, I give!

YEP...it'll cost ya if you throw parts at it, that's for sure.
But, with a bit of testing, you can narrow it down to the failing component.

First thing I would do is get an inductive timing light and put it on each spark plug lead one at a time. Look into the light when it is doing it's acting up dance, and determine if the spark pattern on all six looks the same when looking into the light. Look for obvious misfiring on one or more cyls. Note if they are on the same bank or not. Use your head...don't add variables....keep the testing the same for all six. Same RPM, etc.
Then it may clear up for you as you describe. If it does, look again for any difference in the timing light when it is running good.

And yes, you will be on the water when doing this looking....don't fall off the back.

If you see erratic timing light behavior, look for loose connectors to the packs, corroded or pushed back pins in the rubber connectors from the timer base and stator, and if you can pin it down to one side, you have the benefit of being able to swap packs to see if the problem follows the pack. I didn't look this motor up...but I am pretty sure it does have two packs.

If all is right with the light on all six....all look exactly alike at the speed where you are having trouble.... I would say your problems are not ignition related.
You can obviously do the correct DVA measurements and spark gap jump tests, but the timing light method is a rough go-no go way to check ignition. Plenty of posts on here how to do those correct tests if you want to dig deeper into the ignition system.

If you cannot pin it down to ignition, pump the primer bulb when it is acting up. You will be providing a "manual boost" to the existing fuel pump, which may be weak and failing. Surging being caused by a bad fuel pump. Maybe.

Do those things, and post back. But don't just throw parts at it.

Oh and by the way...all these tests are free....don't cost a thing. Timing light can be borrowed at AutoZone and returned....etc.

Re: Okay, I give!

daselbee said:

YEP...it'll cost ya if you throw parts at it, that's for sure.
But, with a bit of testing, you can narrow it down to the failing component.

First thing I would do is get an inductive timing light and put it on each spark plug lead one at a time. Look into the light when it is doing it's acting up dance, and determine if the spark pattern on all six looks the same when looking into the light. Look for obvious misfiring on one or more cyls. Note if they are on the same bank or not. Use your head...don't add variables....keep the testing the same for all six. Same RPM, etc.
Then it may clear up for you as you describe. If it does, look again for any difference in the timing light when it is running good.

And yes, you will be on the water when doing this looking....don't fall off the back.

If you see erratic timing light behavior, look for loose connectors to the packs, corroded or pushed back pins in the rubber connectors from the timer base and stator, and if you can pin it down to one side, you have the benefit of being able to swap packs to see if the problem follows the pack. I didn't look this motor up...but I am pretty sure it does have two packs.

If all is right with the light on all six....all look exactly alike at the speed where you are having trouble.... I would say your problems are not ignition related.
You can obviously do the correct DVA measurements and spark gap jump tests, but the timing light method is a rough go-no go way to check ignition. Plenty of posts on here how to do those correct tests if you want to dig deeper into the ignition system.

If you cannot pin it down to ignition, pump the primer bulb when it is acting up. You will be providing a "manual boost" to the existing fuel pump, which may be weak and failing. Surging being caused by a bad fuel pump. Maybe.

Do those things, and post back. But don't just throw parts at it.

Oh and by the way...all these tests are free....don't cost a thing. Timing light can be borrowed at AutoZone and returned....etc.

Click to expand...

Thanks for the info!!!!!
Can an inline fuel pump be put on this motor? I am disconnecting the VRO this weekend at the request of every boat mechanic I talk to.

Re: Okay, I give!

Inline fuel pump? Not sure of the terminology.
If you mean an electric fuel pump auto style...not recommended. Too much of a fire hazard.

You may be able to retrofit it with an older style "house shaped" fuel pump, but you will have fuel flow volume problems considering it is a V6.

You can disable the oiling function of your existing pump. There are MANY MANY posts on how to do that. JUST be SURE to PRE_MIX!!!! I think that is really what the guys are recommending...disable the oiling and go to pre-mix.

Search function works well.....hint hint

Re: Okay, I give!

No, I know how to disconnect the VRO, but what I couldn't find in the search is putting an electric inline fuel pump on it should the VRO combo be bad. If fuel pump is bad you have to buy the whole unit. Looks like someone would sell a retrofit kit for this!!!!! In all my google-fu skills I haven't found this!

Re: Okay, I give!

I have seen posts where the VRO has been replaced by a fuel pump and then you have to premix your gas.
You might want to start another post labeled, Eliminate My VRO, or something like that. It might catch the eye of someone who has done it.

Re: Okay, I give!

Problem with electric fuel pumps is there is not a good way to turn it off in the event of an engine stall. The key is still on, the engine has stalled (for whatever reason) and the pump is still running. Now, on the surface, that should not be a problem. The needle/seat in each carb will close off fuel flow, right?
Maybe so, maybe not. If the engine is not well maintained and fuel lines are leaking, or a needle/seat is faulty, the pump will continue, filling the under cowl up with gas fumes....a potential fire hazard.
With the OMS/VRO pump, the fuel is only pumped when the engine is running/turning.

I too would like to see a reasonably priced OMS pump on the market. They are way too high....

If a switching circuit could be developed that would shut down the fuel pump when the engine is not running...even with the key on...that would be great. I would think that tapping into the tach circuit as the sense input to the circuit would work.
As long as the tach signal is there, the circuit allows power to the electric fuel pump....don't know if that exists.

Re: Okay, I give!

Oh, also, regarding retrofitting....older V6 engines before the VRO days had two of the "house style" fuel pumps in series...just to keep up with the large fuel demand that a V6 requires. Kind of a clunky way to design, I think. Best bet is to get a 5007422 (non oiling) replacement pump. It costs just a little less, bolts right up, and then you can pre-mix.

Re: Okay, I give!

daselbee said:

If a switching circuit could be developed that would shut down the fuel pump when the engine is not running...even with the key on...that would be great. I would think that tapping into the tach circuit as the sense input to the circuit would work.
As long as the tach signal is there, the circuit allows power to the electric fuel pump....don't know if that exists.

Click to expand...

Could this be done with a relay off of the regulator/ rectifier? Make the RPM signal wire the wire that supply's the signal to power the relay on the electric inline fuel pump. I don't really know, just brainstorming and looking at the alternatives.

Re: Okay, I give!

I think you might be over-thinking your problem. If you had a new boat, and cosmetics were perfect, I would probably go your route. However, in your position, I would probably mount an electric pump and a simple toggle switch (3.99 at your local Walmart). Of course, use heavier gauge wire and waterproof connections, and make sure you put an inline fuse on it! This would probably fix your situation (fuel pump question, anyway) and all you have to do is flip another switch.

Chris

Re: Okay, I give!

RobbyA said:

Could this be done with a relay off of the regulator/ rectifier? Make the RPM signal wire the wire that supply's the signal to power the relay on the electric inline fuel pump. I don't really know, just brainstorming and looking at the alternatives.

Click to expand...

That is just the issue...I don't know if the tach signal will drive a relay pick coil. I don't know what that signal looks like...I am pretty sure it is pulses that increase with RPM. The tach then counts the pulses. Or, it could be an AC signal that the tach counts every time the signal passes thru zero volts. I just don't know.

Anybody out there know what the grey tach signal looks like? Voltage, etc?

I don't have access to an oscilloscope....I would love to see some of the waveforms that these OBs produce. The stator output to the reg/rect, the stator output to the powerpack and the timer base output to the pack....

A relay needs a source of current to drive the pick coil....I don't think I want to risk blowing my reg/rect by experimenting. But it is possible that it could drive the relay.

As for the simple switch idea offered...I know without a doubt that I would forget to turn off the fuel pump. No kidding...I would absolutely forget, and I cannot risk that.

Don't get me wrong. I like the idea of an electric fuel pump. No more pumping the primer bulb. Lower cost of repair...And the newer E-Tecs have an electric lift pump designed in. Computer controlled though.