verado 300 problem

[century]

hi all , having a problem with a new to me verado 300, starts and runs on the button but when you give it full trottle it falls back to about 3000 revs ? i can coax it up to 4800 revs slowly , but if you put trottle down fast it slows down ?? not familiar with this engine so would greatly appreciate any info 🙏 its sitting on a shearwater 860 , which we just got this week . only 140hrs on it

[mhill]

I’d start with the fuel, then get it plugged in to a diagnostic machine & then start with plugs & coils packs.
Though fuel quality & good tech with diagnostic equipment is the key.

[smallribber]

I suspect it is the ECU holding it back for some reason. Clogged fuel filter would be a good place to start and potentially very easy

[Matt]

3K rev limit is guardian mode. I don't have the Verado service manual (I only have an optimax one to hand) here for the list of things that trigger it - but I would expect either a warning to come up on smartcraft, or you need to get it plugged in to a DDT.

I wouldn't run it until you know what the issue is - some of the causes of the 3K limit could cause damage if you keep pushing it - although equally likely it's just a sensor or loose connection. Specifically, if I have guardian mode trigger I'd only run it enough, gently, to get back home safely and not run it again until diagnosed.

Did you buy the boat & engine together from Bembridge Marine (they make the shearwaters?). Jim that runs it has a really good reputation - while he won't be able to plug a DDT (wires are not long enough to reach), if it all came from him I'd give him a call - he's a Mercury dealer too.

And certainly any local mercury dealer will have a DDT - you'll pay a bit for them to plug it in, but since the actual DDT units cost thousands, it's only fair. Unless you are super keen - in which case, I can give you a link to a US place where you can buy your own.