Help! unable to maintain power
 

Last run of the year last summer and I started having trouble w starboard engine. Starts fine. Idles fine. Run both engines upto 2800 rpm and goes on plane. Go up to 300 rpms and motor stutters for a second and drops to 2500 rpms. comes back up to 3000 then drops to 2500. If I throttle more and go to 3500 the lag gets worse and still drops to about 2500 and takes longer to hit again and get back upto 3500. If I go w more throttle I could get it to stahl. When I run it on the hose I can tell anything is wrong. I replaced the cap and rotor and coil becasue they were 8 years old and did the other motor earlier in the year because the coil died. Checked fuel filter and it was totally clean. Swapped fuel pumps. I did those things but was never able to get on the water again to see if anything happened. Its mid winter and thought I would see what the wonderful world of OSO would have to say. Btw It ran fine the day before. All gauges reading normal

Sure sounds like fuel starvation to me Pete.... were you able t monitor fuel pressure?? Are you carbed or efi ?

ya like phragle said we need more info on the engines, sounds like a fuel issue or timing not advancing

I had 2 similar issues.
1. My secondaries got contamination in them and boat would run great until the secondaries were opened.
2. Ground wire loose/broke (inside shrouding) on my ignition box.

They are carbed 600 cu in. MSD ignition. Fuel pressure stays steady.

How old are the plugs ? might want to swap ignition boxes and see if the problem follows.

Plugs are 7 years old. Irridium plugs. My next 2 thoughts are to swap boxes and carbs (one thing at a time of course) but I wanted to see if there is something I haven't thought of yet.

I'm thinking the carb is flooding, needs cleaning

Im gald you said that. I did look at the float/fuel level through the sight glass. It was normal when not running. But does that mean anything? Also, would it most likely be the secondary float or primary?

It runs fine at idle and up to around 2800, then issues start, so I would look at secondaries. F-2 has a good point with the boxes

What carb model?

Holley 850 cfm 4150

What kind of AFR's are you seeing at WOT, I figured you were running dominators with 600 inch engines

I really cant tell ya.

Swapping boxes might be the easiest, but wonder if a carb swap would fix

Don't forget the dist swap also if there's anything left under the cap. Im not sure what you mean here.

I had just filed the tanks and they were very low on fuel as I was about to do a poker run. The thing is about the gas is the other motor has been fine and both motors ran pretty hard for about 30 min on the new fuel. Then the next day after a long idle to start the poker run is when this all started.

I forget exactly what intakes I have Dart as I recall. Cant tell you the cam. These were built by Goodwin performance in WI. The guy that built the engines in pure platinumII

long idle on 7 yr old plugs, you may have some fouled out, the plugs need to be changed in both engines

MSD distributors have a bad habit of corroding badly under the cap.

Well I have a new cap. But is there something under the rotor I should look at?

look for excessive corrosion.....

Aluminum heads. And Im not changing my plugs till I have to. I dont think I can without taking off the headers and Im not doing that. I mean I looked under the rotor when it was off and the springs looked rusty but IDK.

it Did not look like this. http://69camaro.nextmill.net/photos/distissue/dist3.jpg

I dont get this statement. If your having a problem and your plugs and cap were all 7 to 8 years old why wouldn't you do a complete tune up to both engines. Plugs, wires, cap, rotor, and all fuel filters/ separators. It's a good bit of simple work but it solves alot of little issues on old worn out parts. I only have to maintain one engine in my boat but if it needs maintenance I do it not just half of it at a time. IMO I would start with a full maintenance tune up and this way both engines have full tubes up at the same time intervals. Good luck I hope you get it sorted out.

i agree with others on here,,,,sounds like fuel issue........

i had a similiar issue on my 34 sea ray..boat would run fine 3000 rpm, then the port motor would start losting power
if i gave it more throttle it would stall out...but would idle forever
i think there was issue with tank...garbage...old...etc...


sway carbs coils new fuel pump,,new fuel line..
never figure it out .
sold boat......

I've also had the exact same problem in the past on a 454 mag. Ended up that I developed a soft spot in the fuel hose feeding that engine. You couldn't detect it by just feeling the hose for soft spots. Ended up finding out by hooking a portable fuel tank to the engine that had the issue, ran it up to WOT and problem was gone. Ran a new fuel line to the engine and problem solved. Still was very difficult to find the soft spot that was collapsing on the old hose after it was replaced.