Whats holdin me back?!?! UPDATE!

[JDSkier91]

I checked the timing today and it was a little off. We adjusted it, but I have not had a chance to take her out on the lake yet to see what the top end is like. The thing is… I am having another problem. Every time I start the engine on a cold start it fires right up, idles well, but after 2min it just shuts off very sudden, it does not putter. It just turns off. After that, it will not get going again unless I let her sit for a few minutes. I repeat the cycle a few times and then it will run fine the rest of the day. I don’t know if this is related to my lack of power, but fixing the timing did not fix this issue. 

[Mike Harry]

Compression and bleed down test next? Possible transmission problem? That what I would check next and in that order. But that's just me. Are you sure the Carb is getting to wide open throttle?

[JDSkier91]

I have never done a compression and bleed down test... but I can prob figure that out. Trans seems fine. I put a marine carb on order.

[Mike Harry]

Easy to do, and you can "borrow" the tool from auto zone or any of the likes. basically you pull a spark plug and spin the motor over to see what your compression is.... then leave it sit and see if the number goes down (if you have leak down)

This will tell you if you have good compression and will also tell you if your rings or valves are not holding properly. If you dont have any compression...... sadly you can skip the leakdown test cause that aint good.

I see you ordered a new carb, but have you ever went to the carb you have and made sure the throttle is opening all the way? someone may have adjusted something (on the cable or if it has been replaced) incorrectly so the butterflies are not opening fully.

with the motor NOT running, push your throttle lever all the way forward. Then take a look at the carb linkage. See if you can push the throttle linkage open further by hand. If it wont move at all you may need to pull the cable off of the linkage to check it, but in either case, if the linkage goes further forward than your cable is pushing it, then you dont have wide open throttle and that could be your problem.

[JDSkier91]

I'll try the compression check this weekend. As far as the carb goes... I can not get it to go over 3000rpm under load but if i take it out of gear I can rev the engine to 4500rpm. I will still check the linkage when I check the compression.

[daveo]

Before you spend to much money check your fuel lines all the way back to the tank, remove fuel/water separator housing and clean. also check the elbow and anti siphon valve on top of the tank (small elbow with spring and ballbearing ) It may not be the problem but it sounds alot like the prob i had. there was debris in the anti siphon valve restricting the fuel flow. mine would start right up and die as soon as it burned the fuel that was in the line. Like I said may not be the problem but its always good to rule out the small things first.


                          daveo

[RonT]

I re-read your posts, you are describing 2 different symtoms, dying after 2 mins then runs "fine" issue & lack of power under load as the other. Electrical & fuel issues can cause both, mechanical issues doubtfull. If you could list a known history of the performance and what you have done or replaced I will forward an opinion. Feel free to call, its got to be easier than the dual vanos timing problem I'm working on today.  RonT 985-542-4336

[JDSkier91]

Gongchuan, I checked the compression, everything seems fine there. They were all 125-135, so I think that’s good. Right?
Thanks daveo, I’ll give that a try. I like the idea of not spending to much money… I feel like I have already replaced half the engine.
As for where the engine is at…
Last summer when I got the boat I remember it going around 40mph. Then I had a tick for awhile, turned out to be a collapsed lifter. So over the winter I replaced all the lifters. So far this year for one reason or another replaced the following:
New starter
New impeller
New fuel filter, oil filter, and oil (also have been using Valvtect Ethanol treatment in gas)
New oil pressure sensor
New neutral safety switch
New fuel pump
New fuel line (from pump to carb)
New carb (as of this past weekend)
New igniton switch, coil, spark plugs and spark plug wires (also this past weekend)

When I say the engine ran ‘’fine” I was referring to it sounding fine when it was not under a heavy load. It would run smooth and not backfire.The boat seemed to struggle getting up to speed with 3 people on the boat pulling a tub with 150lbs on it. If I took it up to 3000rpms it would start to backfire a little. It would do the same if I gunned it from idle. It also occasionally backfires when trying to start it.
We thought it might have a timing problem so we checked the timing. Moved around the timing and the dwell, neither helped (if anything made it worse, so we put them back). Now it seems like the problem is getting worse. I can not drive the boat at all. It starts up, sounds fine then shuts off after 20sec to a minute. If I let it sit a few minutes, it will crank back up, but soon dies again. If I try to start it right after it dies, then it won’t start.  It seems like it is cranking slower now too, even with a new starter and fully charged battery.
Specs
91 AS Advance,351 W Indmar, Holly 4160 Marine carb(new), Prestolite breakerless marine distributor, Prop:  OJ 13x13 4blade legend

[Mike Harry]

Don't replace it just because I say this but the ruff running and backfire might be the coil?.....

[JDSkier91]

Yeah, but we put on a new coil.

[Mike Harry]

My bad, I was called out EARLY this morning and half asleep when I went through your last post....... now I see.