Do I need new exhaust manifolds?

forget about the exhaust manifolds, they have nothing to do with this...

when was the last time you ran the boat fine? what work has been done on it since?

Tom,

You say it runs good on the trailer, are you able to get it above idle in neutral? Manifolds could not do this. Could your throttle/trans linkage be messed up?

have you varified that the throttle cable is actually moving at the carb while your underway? have you changed props?

Seems really wierd it doesn't increase any,

Well, the last time it ran perfectly was right before the RWP impeller went a couple seasons ago. After that,I couldn't get it to run properly. After the impeller was replaced, cleaned chunks of impeller out of my t stat housing, and some came out of the exhaust manifold plugs when I drained them too.    I swore it was a carb issue, but after the carb had been checked out by a holley carb guru (not a ski boat carb guru, but he has done a few ski boat carbs with no issues), and I learned a LOT about carbs by trying to see what the issue was if it was carb related. Nothing after looking at the carb many times tells me it is a carb issue, but i could be worng.

It would run, but cut out after it got on plane. Sometimes it would take a while and I could ski behind it, other times it wouldn't let me ski.

I did a compression test with the original heads on it, and it looked fine. I thought maybe I had an intake manifold air leak, so while I was at it, i got the edelbrock performer, and while i was at it, got a set of gt40p heads that were fully rebuilt by a trusted machine shop. I figured with the original head gaskets, that might have been the issue. So I put new top end on it, all gaskets, the newly refurbed heads, the perfomer carb, tested the fuel pump and it works and does not let gas past the first membrane so that is fine apparently.

While testing and redoing the top end of the motor, I saw the fuel line was original from the tank to the fuel water separator. When i replaced that, i found what i believe to be my issue of the motor cutting out. There was crap in the fitting right off the top of the tank. I wish i would have found that a long time ago. i bet the boat would have been fixed with that alone.   who would have known? but I hear I am not the only one to spend a lot of parts only to find it was very cheap fix even with the new gas hose.

it runs great out of the water, but bogs and dies in gear on the lake.

Yeah, I looked at it tons of times last year. I am positive the firing order is right. I even tried a couple different alternate firing orders, but none would work well on the trailer besides what it is using now.

oops yes, 500. Even if it had 5000, with the new top end that probably wouldn't be an issue, at least with the good compression I have on it.

My compression did go up with the new heads and gaskets, but not a lot. it was fine before the head swap.

I will be bringing the CC down home here from the cottage so i can work on it. if i can't figure it out, I will take it to the mechanic, but I HATE to do that. And I would hate it if it was something stupid that they charged me a lot of $$ for. For em time is still more plentiful than $$$.

I'm hoping to have this boat at the green lake reunion for my first time there.

if it were distributor related, it wouldn't rev and run like a top on the trailer, right?

horkn wrote: It would run, but cut out after it got on plane. Sometimes it would take a while and I could ski behind it, other times it wouldn't let me ski. .

This is where trouble shooting over the internet gets tricky, you have to give us consistent information. You originally said it won't rev above idle in gear, but now you say it gets you on plane for a little while and then dies.

Try a new coil. Is there a balast resistor inline?

This is the plate hotboat is talking about, is this what you have in place

That plate is exactly what I have.

Mine is a summit brand.

I wish I had someone in the area with a known perfectly set carb to try out.

It sort of does sound like it runs out of gas when powering up out of the hole on acceleration to me, but IIRC,I now have the float set pretty high so I was trying to eliminate that as an issue. I think if I set it any higher, it would spill gas out of the tube. I tried adjusting this in the water too when I had an issue, and I was not able to get the floats set in any position to get it to power out of the hole properly.

The accelerator pump does spray gas when activated. I have no clue if the cc of the pump is the right amount, but it ran with this carb before it was checked out. i doubt the accelerator pump was even messed with.

If I were to buy a brand new holley 600 cfm marine carb, would it literally be bolt on and not need adjustment? I really don't want to throw a good chunk of money at the boat, but I want to get it running finally.

I would rather buy a used known nice one due to cost, but even if the fuel line inlet was a tad different, that is not a big deal to me.

Anyone know of someone selling a nice used carb?

Fuel Pump OK?

horkn wrote: the fuel pump pumps well, although i have yet to put a psi gauge on it. It does suck up fuel quickly from the feed hose,

OK couple comments. First don't spend any money on a carb, adjust what you have. Secondly just because you checked the fuel pump for a leak past the diaphram only verifies it's not leaking and does not say anything about the amount of fuel pressure it suppliers. So assuming the fuel pump is ok is a bit risky in my book.

So sollutions for the problem, couple of basic checks are require and all can be done in the drive, but first, check the anti-siphon valve at teh fuel tank make sure it's clear, next get a fuel pressure gauge disconnect the fuel line at the carb and crank the engine over a couple times to verify you are getting 5 lbs of pressure. Next you need a timing light and need to verify that the timeing is set between 8-10 BTDC, next you have to verify the mechanical advance is working properly, crank the motor up to 2500-3000k and verify your getting upper 20's to low 30's of total advance. Once all that is verified it leaves the carb.

What needs to be check at the carb is the accel pump, disconnect the cable at teh carb slowly move the carb's throttle open watching for a stream of gas to squirt into both primary barrels for the entire range of the throttle's travel. If the stream starts half way throught travel that's not good and it needs adjusted, there is a little screw/nut adjustment by the diaphram the needs adjust until you get a full stream of gas for the entire stroke of the throttle.

Now if the float is too low then it's going to lean out the carb and usually backfire through the carb, now if it's too high then it bogs down the motor.

Basicly your problem is ignition timing related not enough advance over the rpm range or a fuel delivery problem. So do the easy stuff first, fuel pressure and timing verification, then move forward to teh carb.

What type of ignition system to do you have? points. electromic, conversion?

engine bogging down under load causes,

Flooding
Retarded timing
lean setting
no fuel pressure
no fuel volume
bad accel pump
bad coil
bad module

just because it's sucking up gas doesn't mean it has enough pressure to lift the needle off of the seat in the carb so get the gauge and double check.

take a buddy with you to drive or watch the carb, lift the engine cover remove the arrestor but some power to it and look and see if fuel is being sucked from the front of the primary barrels, it should only be coming from anular ports in the center of the barrels. Take some carb cleaner or starting fluid, once you are going and the throttle is opended up and it's bogging down spray some of it accross the top of the carb's primary barrels if it takes off your not getting enough gas if it boggs down more then your flooding it and the float might be too high or your mechanical aadvance isn't working in the distributor. Your correct on how to check for total advance BTW. It's easier if you have an adjustable style timing light to verify it otherwise you have to take a guess as the scale on the block doesn't usually go high enough.

You have point in it now the module was removed when you replace the conversion with the points. Now since you have re-installed the points did you set the dwell? you can get close by setting the gap but it can be an art getting it exactly right with that method so a dwell meter is your best friend in this case. You'll want to go back and readjust timing if you have to change the dwell, set the dwell at 28-32 degrees.

If it is way off you'll want to readjust everything, timing idle air mixture screw, idle too as these will change with changes to the dwell and timing.