Sticky/Clogged Injector maybe ?

Hello gurus ,

Ok so 3 weeks ago we had the boat out and it seemed to run perfect as usual . Fast forward to Saturday as soon as I started it I knew something was off . It was missing real bad and shaking like it needed a tune up and also down on power we didn't do any towing just drove to a friends place and hung out and drove back to the ramp at the end of the day. So instead of going out Sunday we stayed home and I found the dist cap was really corroded so I decided new cap, rotor, plugs, and wires was in order . Well they didn't have the wires so I did everything else including a new fuel filter. yesterday we dropped the boat in and it was nice a smooth running again so we thought we were good to go . Once we idled out of the 5mph zone and throttled up I could tell it was much smoother but still down on power . So we anchored in a cove fairly close to the launch and spent the day swimming and getting sun burnt .lol. While the family was out swimming I fiddled with the engine to see if I could figure out what the heck was going on . This is where I found something a little off . I decided to just grab the injectors while it was idling and you can really feel them opening and closing as the signal pulsed to each one . Except one of the injectors I could barely feel that one opening and closing . It felt like it was getting the signal but the either it was frozen and trying to open and close or maybe had blockage keeping it from opening and closing . I know this is a really unscientific way to diagnose a sticky injector but maybe its the reason it runs smooth at idle but down on power under load. I'm going to slap the noid light on the injector plug and make sure its getting signal which I think it is . I have a set of injectors from a very low hour salvaged boat of the same vintage that look identical so I think I will try to sneak a new one in that hole and see what happens . What do you gurus think what else can I do. Give it to me straight guys I can handle it. 😆

sounds like you found the issue. likely not opening all the way up at higher RPM. check the wire on the problematic injector for corrosion or nicks in the coating.

Before you go messing with injectors, put a fuel pressure gauge on and check your fuel pressure. Could be a bad fuel pump. Unless your boat has sat for 3-4 years unused, injectors typically dont go bad or get stopped up unless your rubber fuel line is deteriorating.

Thanks for the replies guys !! My fuel system is pretty clean and there was nothing in the fuel filter that I could find . Im going to swap the injector this afternoon and take it our again this weekend and see what it feels like .

So Replaced the injector and cleaned the spark arrestor and the boat runs much better but still not right just yet. I am embarrassed to say that I cant even remember the last time I cleaned the arrestor it was terrible. Going to check into an antisiphon valve issue and find a fuel pressure gauge to hook up and do some testing .

You said you replaced the plugs, cap, rotor but no the wires. Read the resistance of the wires and make sure they are all within a certain resistance of each other. If you find one with higher resistance than most of the others that may point to an issue as well. Also pull the plugs and read the tips... might show you if a cylinder isn't firing, too rich/lean, or oil fouled.

I agree to check fuel pressure as well. I think you're on the right track, but there's a few more things you can check without spending money that may pinpoint the issue.

Out of curiosity was your cap a crab cap design with the plug wires coming out 2 sides vs on top. If it’s the crab cap design they are notorious for shorting out internally. Even new ones out of the box are sometimes bad. Just a thought as well.

The problem is now figured out I don't know how I didn't notice this as the issue when I tuned it up as I am a bit embarrassed to even admit it .
The dang ole exhaust manifolds were leaking on the plug and wire and causing to run like crap intermittently. I ordered new manifold as they are rotten and very old. When I went to replace them I found even worse issue which I think is more the culprit then the manifolds. CRACK HEADS ..(Insert crying rolling around pounding the ground emoji.)

The crack is right above where the plug wire that was getting saturated is and I have a feeling got worse over the winter then it was last summer. Now to decide if a band aid is in order to save my family's summer or full rebuild.

Originally Posted by TTyler89

Out of curiosity was your cap a crab cap design with the plug wires coming out 2 sides vs on top. If it’s the crab cap design they are notorious for shorting out internally. Even new ones out of the box are sometimes bad. Just a thought as well.

Wires come out the top of the cap.

Wasn't just the manifolds that rotted out from that brackish delta water but also the vortec cylinder heads these boats come with as well. ( Vortec Heads are thin) Corroded right through the head castings. Luckily a friend had a sweet set he was going to get rid of and he hooked me up with them. Swapped them out and looked at the cylinder walls which looked surprisingly good and put it back together. Everything was fine except after few trips it starting idling rough and smelling like excessive fuel. From what I can gather the only thing really regulating the mixture is the MAP sensor so I am trying to find one. I swear I remember a car sensor that was the exact same but cant for the life of me remember what car it was off of.