View Full Version : 92 Prostar 190 with 351 running rough question

92 190 PS
04-27-2013, 05:32 PM
92 Prostar with a 351 HO that I'm getting out for the first time this spring. Worked on it yesterday changing fluids and running in driveway and everything was great. Ran it for 15 minutes or so to get it up to temperature and again when I was done and everything worked well.

Today before changing plugs and doing a couple more finishing touches it is not running well. Starts quickly and runs as long as you give it gas. If you try to hold any RPM or idle it won't stay running. Pulled the fuel filter in the tank (On the end of the fuel line) and cleaned it. Changed the plugs and still no progress.

Looking for the next things I should check?

04-27-2013, 07:28 PM
Still running the original mechanical fuel pump?

Maybe the diaphragm let go ...... Any exhaust details? Whitish smoke?

92 190 PS
04-27-2013, 10:44 PM
Yes still the original fuel pump. Any simple way to check the diaphragm?

As for smoke, don't notice anything out of the ordinary.

04-28-2013, 12:15 AM
Start with the basics:

New plugs are good....gapped correctly?
Points or electronic ignition?
What is the age and condition of the distributor cap and rotor?
Same goes for the spark plug wires.
What is the idle speed set at?
Is your electric choke fully open after about a minute?
How much old fuel in the tank and was it treated when you winterized?
Is timing correct?
Has the carb ever been rebuilt? Is it a 4160 or a 4010?

Once you get through that, I would look for a vacuum leak. Spray carb cleaner around the base of the carb with the engine running (use caution here as it's flammable). If your engine speeds up with the carb cleaner, you found your leak.

That should keep you busy for a while:rolleyes:

04-28-2013, 01:03 PM

92 190 PS
04-29-2013, 09:49 AM
Just an update for anyone that has similar issues in the future.

Pulled the fuel filter out of the bowl on the fuel pump and replaced it. Pulled the two inlet tubes off the carb and flushed them. Sprayed some carb cleaner in through the carb a couple of times.

Re installed everything and now the boat runs great again. Guessing there was some dirt in the lines somewhere. Hoping to run the fuel I have in the boat ASAP and start with a fresh tank for spring.

05-27-2014, 04:14 PM
Realize I am responding to an old post but having the same issue on my 92. Got it out for first run after winter and ran great all weekend, that is until the last run of the day. At that point the boat started to lose speed and RPM and forced me to come to a stop. It never died and when I would accelerate again, all was good and it would run but then randomly lose all speed and come to a stop. Initial start-up was fine and idle was fine, though admittedly as the day went out, I noticed cold start each time we went out would require me to give it some gas in order to stay running.

I have read on here about spark plug changes, fuel pumps, etc. I did winterize it and treated the gas. Tried to run most of that old gas out before refueling. Did not do a tune-up this spring as I had done that last year.

Any thoughts based on this? I know there are many things to begin analyzing and I am not mechanically inclined. Boat does have perfect pass and therefore has the dial to set the right tension for the throttle cable. I did loosen that prior to last outing because I was noticing that unless I keep my hand on the throttle, I progressively lose speed as the throttle comes back toward idle. So I did wonder if that adjustment had anything to do with it.

05-27-2014, 04:23 PM
My quick thought is that the mechanical fuel pump is starting to go ... they lose pressure at high rpms and don't seem to affect idle at all ... I had one that was going bad and the kids could kneeboard (20 mph) .... but I could not slalom because the engine would starve for fuel ....

Mechanical fuel pump easy to get (skidim.com) and my best guess ....

05-27-2014, 08:59 PM
Um...fuel filter out of the bowl on the fuel pump? Gonna have to go look at mine. Fuel filter in the tank? Man, I gotta start spending more time back on this forum.

05-29-2014, 12:51 AM
I wonder if given it is the first run of the season and I had some old gas with stabil in it and then I added new gas if I might be dealing with some issues there. Thoughts on adding the Startron product to the tank http://www.starbrite.com/category/marine to reduce the phase separation I might be experiencing which in turn could be causing the issue>

07-14-2014, 10:52 AM
So I was out again this weekend and having the same issue. Only thing I did in between runs was to siphon out all of the old gas and replace with all new and some of the fuel enzyme treatment.

Fires right up, runs smooth in idle, cruises at around 20 fine. But you hit the throttle to take off and she backs off and sits down, sometimes dies. I can pull kids on a tube, but that's about it.

I am pretty sure it has to do with old fuel. First run of the year was as good as ever for two days, but then this issue started happening. Has to be a fuel related issue. So would the next step to be replace the fuel filter, then progress to fuel pump, then start thinking it could be the carb?

I will take the advice of changing the filter and spraying carb cleaner in and hope for the best. What do you do on that, take the flame arrestor off and spray directly in while running?

The difficult thing is that I have to trail to a lake, so testing is more difficult. Only way to know is to put the boat under load, which I am not going to do in my driveway. Anyone know if a marina with a shop can test under load with high throttle?

Any other initial suggestions would be welcomed.

07-14-2014, 10:55 AM
I am still thinking fuel pump (if you have a carb version) then that would be the old crank driven low pressure fuel pump that would act like you mention now ... poor high rpm performance yet ok at low speeds.

07-14-2014, 11:27 AM
OK, I appreciate the input. Yes, this is on a 92 with the carb.

Is this the right one? Any tips on the install? Something a novice can do?


07-14-2014, 11:31 AM
Easy to do .. minimal fuel spillage (but as always be careful anytime with fuel) low pressure so no real issues .. just remove lines, remove from block, and put the new one into the block and re-attach the lines - 20 minute job.

I hope that does it for you ... I did the same on my old 93 190 with 351 ... it would run fine for kneeboarding, but could not handle the slalom or barefootin ... replaced the pump and all was well.

I hope that does it ... really hard to troubleshoot via Internet symptoms but I would bet a rum and coke on it. Peace.

07-14-2014, 11:41 AM
Great...I am going to move forward on the pump. Just one other thing, with input on this being related to distributor and replacing the cap. Wouldn't you guess that if I am getting no issues with spark that it is more likely somewhere else? I think first thought is to do the tune-up, but given the high rpm issues, everything says it's the pump. I have the rubber flexible fuel lines, so I guess skidim also recommends picking up the metal version.

07-14-2014, 12:13 PM
Do these old mechanical fuel pumps act intermittent? For example, might it run fine at higher RPM's then bog and act underpowered at various times?

07-14-2014, 12:15 PM
No, since the problem started, I cannot get the high RPMs at all. It backs me down and if I keep pushing it will die.

07-14-2014, 12:29 PM
I had this same type problem with my 93 this spring. I ended up replacing plugs, plug wires, distributor/ rotor, fuel pump, filter and rebuilt the carb. Still gave me issues. Pulled the anti-siphon/check valve on top of the gas tank and there was debris. Cleaned it out and have been running solid since.

Dino Don
07-14-2014, 12:37 PM
Do these old mechanical fuel pumps act intermittent? For example, might it run fine at higher RPM's then bog and act underpowered at various times?

Interesting discussion: my 87, which I purchased new, 650 or so hours and is still running the same pump. Guess I may be fortunate to say that but also it may go out at any time. Doing a handicap skiing event for a rehab hospital this weekend might need to think about it??

07-14-2014, 12:39 PM
OK, that is intriguing given you did all of things recommended. So is this check valve something you get to by pulling out the back seat and it attached where the fuel tank is hooked up? How do I get to it?

Looks like another string on this here:

07-14-2014, 12:44 PM
Have you confirmed that you accelerator pump is functioning? Simply remove the flame arrestor and, with the engine off, have someone go to wide open throttle and see if you get good fuel streams on both sides of the primary (front) side of the carb.

07-14-2014, 01:10 PM
Yea you have to remove your back seat. The anti siphon is on top of the fuel tank. A 90 deg elbow with a ball check valve. It is where the fuel line comes out of the tank. Its not hard to check, honestly should have been one of the first things on my list.

07-15-2014, 09:47 AM
Interesting, my 92 doesn't have such anti siphon/check valve. I can look down and see gas by unscrewing the cap. Just a straight hose that connects with the tank. I will check the accelerator pump and if that is good, I have to think it is fuel pump related.

07-15-2014, 11:15 AM
Lots of good advice, but I think Peter is on the mark. Make sure you are getting a steady stream of fuel out of the primary squirters in the carb then work backwards from there.
I chased down a bunch of gremlins when I first bought my '92 PS 205. Though a little different from what you are experiencing, I traced my worst issue back to a failing coil. I had replaced all filters, rebuilt the original carb, new plugs, Ignitor II conversion, etc.. but it would start conking out after running for about 45-60 minutes. I was convinced it was fuel related but was getting a healthy squirt of gas when I checked on the water. Put my hand on the coil and nearly burned my skin off. Put ice on the hot coil and it ran perfect again. Replaced coil and never had an issue since.

Best performance/function upgrade I did was replace that stock carb with a 4160 marine carb. A little tuning and it was like night and day with idling, holeshot and general hassle-free running improved greatly.

Good luck & I'm sure you will solve it.

Worthing skier
07-15-2014, 05:45 PM

Had a very similar running problem ,
ended up being the power valve,
Has the engine spat back through the carb reticently on a throttle opening ?
as this will split the power valve .


07-15-2014, 10:10 PM

I ran the test and yes, the carb opens up and I am getting the expected squirts of gas on both side on the front side, below the choke plate. Back side of carb does not open, but it is not supposed to when not running I expect, correct?

07-16-2014, 01:44 PM
Can anyone comment on how I get to the fuel filter to check and see if it is clogged? Searched the forum but didn't find anything so searched google and found this. I am sure it is not difficult, I am just a novice and not even sure how to get to it.


07-16-2014, 02:11 PM

I ran the test and yes, the carb opens up and I am getting the expected squirts of gas on both side on the front side, below the choke plate. Back side of carb does not open, but it is not supposed to when not running I expect, correct?

OK, so the accelerator pump and nozzles are working. Correct on the secondary side of the carb not opening unless under load and about 3/4 throttle. Even if a person is crazy enough to go to WOT in the driveway they won't open. The engine needs to get down to about 6" of vacuum before the secondaries open. As stated earlier, they can be opened manually.

07-30-2014, 05:00 PM
Ended up not being a fuel issue at all. Figured out that the choke plate was not opening fully when under load, thus not getting air. Engine was backing me off the throttle, which was good so I didn't overheat.

Had to replace the linkage and pin, but still not sure why it was happening in the first place.

09-03-2014, 10:21 AM
Well, unfortunately it wasn't the choke plate and I am still having the issue.

I have done the following:

Pulled out anti-siphon valve to check for clog and it's fine
Replaced the spark plugs
Checked the bowl in the fuel pump and changed the fuel filter

I was planning to take it out and run a direct line from a 5 gal can to the pump to see if I can isolate the issue. Thinking if it does the same thing then it is not something behind the fuel pump causing the issue.

Replacing the coil and replacing the fuel pump seem to be the next logical options.

09-03-2014, 11:18 AM
How fast can you get the boat before it starts backing off and how long does it take before it starts backing off? Do you know if the secondaries on the carb are opening under load? Probably best to take a second person to verify so you don't sling yourself out of the boat at speed.

09-03-2014, 11:43 AM
Have you checked to confirm the secondaries are opening? This could also be a distributor advance issue.

08-08-2017, 11:21 PM
You know you seem pretty intelligent from your reply. I have a 93 prostar 351 velvet 1;1 My manual that came with the boat says Timing 10 btdc I have 1300 hours on it and I thought I would throw a light on it. It was at 6 with no major difference in the way it runs. So What is it 10 or 6 ? Its idling not rough, but almost a rich blub not rhythmic that I can feel when we are idling in a cove. I leaned it out ( New Carb by the way 4160) and can almost eliminate it, but my right mixture screw doesn't have much affect on the idle. Thoughts ? As a matter of fact I can close it down and the engine still runs. How could metering blocks be dirty in one year to make it not respond ? Thoughts? Plugs only have 20 hours on them, New plug wires, last years cap and rotor button which I will turn over and dust it with some paper. Its annoying as I am an aircraft mechanic and picky. Too lean ? Stretched timing chain? heart shaped valves, Hell I don't know so I am asking you. My name is Al