'84 150 BlackMax wont rev past 2000rpm...

[macutty]

Hey guys,

Back on the water and more headaches this year....

I'm having an issue with the motor not reving past 2000rpm. It ran fine the first 2hrs or so of the season but after a half day of boating all of a sudden it would not rev past 2000 rpm.

last year i replaced the fuel pump and all the lines. Already tried the fuel filter....gas is new this season and same as I've always run??

Not sure what could be causing it...I tested the coils and stator and both seem to be fine, working on testing the trigger now...

Any ideas that might cause this? It starts up no problem, seems to idle like a champ but once you open it up it gets to around 1800 and starts to miss fire right when you expect it to hit the power? You get the occasional surge in power for less than a second but it wont rev any higher.

I try reving it in nueutral and it will climb to over 5000rpm but very slowly making me think that a cylinder is missing maybe?

I also did the head gaskets over the winter if that could be at all responsible? (but couldnt think how it could??)

Let me know what you guys think.

Thanks again for your help....I dont know how else I'd spend my vacation if i wasnt trouble shooting my motor with you guys..

Cheers

[macutty]

UPDATE: the triger seems to be fine as well....so I'm really starting to get stumped??

Any ideas out there? Carbs maybe?

[shadowman]

Sounds like the high side of the stator.

[T-REX]

Yea, stator....I juss got thru tseting a stator that check out good...still no charge...replaced stator, charges it'z azz off.....BUT, according to the book, it wuz in specs!!!....U figger

[macutty]

thanks guys....guess she's trailer bound for the res of the weekend....

[ult680]

I had a similar problem, ended up being a primer ball. mine would just die out trying to get up on plane, but run fine at idle. for $20.00 its cheaper than a stator.

680

[j_martin]

At least a little formal fuel pressure or vacuum testing would be in order before buying expensive ignition parts with no positive indication of failure.

hope it helps
John

[macutty]

Hey guys,

thanks for the additional input.

I replaced the fuel line from the splashwell to the motor (including ball) last year. Do you think it could have failed so quickly? I'd much rather replace the ball but dont know how to test the vacum/pressure of the lines to confirm or rule this out....

[macutty]

So.....after much tinkering I figured out my issue: 2 small metal shavings clogging the main jet on the #1 cylinder....who would have thought?

But now I have a new concern: after working on it in the driveway with the muffs for a couple days I noticed the tell tale is pretty much a dribble if anything at all when I'm idling. I'm also getting air being pushed out the relief hole on the poppit cover....could this be the poppit or do you guys think this sounds more llike a blockage? I get decent water pressure on the gauge (8lbs at idle 15-20 at speed).

ideas?

[Wayne Cammidge]

I think you have only found one of your problems.
I have a quick test that I do if I can only run the motor on muffs.
I take my spark tester and remove as many spark plug leads as possible putting the loose leads on the spark tester, as possible that I can still get it started.
On a V6 that is normally 2.
On a V6 if I can not get it started on 2 I know I have a problem with either of those 2.
I will then start it up and run it through it rev range, maybe to 5000 rpm, by doing this you can tell if those 2 cyclinders work okay.
You have put a load on those cyclinders and you have eliminated all the others.
I then run all combinations of cyclinder pairs, compairing running characteristics of them all, will they all idle at same throttle setting, do they all respond the same to accelleration.
This tells you a huge amount about the health of the engine where a trip to dam is not practical, and if I am at the dam will drop individual cyclinders one at a time to eliminate them when I am battling to find a problem.
Hope this helps.
I do not think you need to worry to much about the water pump yet. Just keep an eye on water temp and pressure once you have it back in the water.

[Wayne Cammidge]

Sorry was going to say.
If you are down on one cyclinder should still run a bit better than what you are getting. Would expect it to get to over 4000 rpm in a situation where it normally runs near the 6000 rpm

[macutty]

So I tried the pairing of the cylinders and it seems to be doing the same thing regardless of which 2 I have running at a given time.

Still the same issue: starts/idles fine but misses and stutters above 2000rpm.

It revs better in the driveway on the muffs, but it is still very obvious it's missing once the revs do get up there.

Any chance this could be related to the carbs? this is probably my weakest area and I dont know much about them and what could go wrong. I was lazy at the end of last season and had forgot to run them dry before it went in to storage for the winter so maybe they could be gummed up? But on the other hand it ran fine the first 2 times out this spring....:confused:....I'm stumped.

[macutty]

on a seperate note, I'm also having an issue with the poppit....noticed it was spitting water out of the relief hole on the cover so I installed a new diaphram but the problem remains....new water pump and t-stats got the pee flowing good but I seem to have high pressure (12-14lbs @idle) and this water comming from the poppit.

[donmac]

try syphon valve on the tank, or run it on a portable to test,are the head gaskets on the right way.

[trashy]

Have you tested and/or replaced the stator as was suggested from the beginning?

[Wayne Cammidge]

It could be fuel related, try the sugestion of a seperate tank, prime the fuel system and then take out the new primer bulb, had problematic bulbs before, but does not sound like it.
Stator is sounding more likely, did you do both a DVA test and an OHms test.
If either are out of spec, replace.
Also check your bias circuit, if that is faulty you will have endless trouble, while busy on the bias circuit remove any timing boxes that are conne cted to it, and just to be sure, disconnect the cut off wires from both switch boxes

[flabum1017]

If your'r thinking it's the carbs, pull the carb drain plugs and look at them, if they have a gummy residue on them, the rest of the carbs look the same way inside. Gummed up carbs can give your symptoms.

Have you checked the spark with a spark tester?