• Welcome to Jetboaters.net!

    We are delighted you have found your way to the best Jet Boaters Forum on the internet! Please consider Signing Up so that you can enjoy all the features and offers on the forum. We have members with boats from all the major manufacturers including Yamaha, Seadoo, Scarab and Chaparral. We don't email you SPAM, and the site is totally non-commercial. So what's to lose? IT IS FREE!

    Membership allows you to ask questions (no matter how mundane), meet up with other jet boaters, see full images (not just thumbnails), browse the member map and qualifies you for members only discounts offered by vendors who run specials for our members only! (It also gets rid of this banner!)

    free hit counter

Rotax 250- Engine miss, fuel pump issue

Drothgeb

Member
Messages
2
Reaction score
0
Points
10
Boat Make
Other
Year
2021
Boat Model
Other
Boat Length
22
First time posting here, hope you guys can help.

So I’ve got a 2021 custom built bass boat with a Rotax 250 hp in it. I took it out last week week, and was getting surging and a bad miss. In checking the codes, I was getting P300, P301.

First thing I checked was the plugs, they looked good. But I changed the location of the plugs and coils to see if it made a difference, same thing. After that I inspected and switched the injectors around to see if that made a difference, still got the same codes. But, I don’t have a BUDS to erase the previous codes.

After all of that seemed to check out, I checked the fuel pump pressure. Per what I could find in the service manual I found online, it should be 56-60psi. In checking it with the engine off though, I only had 36-38psi. Since the symptoms seemed to match low fuel pressure, I bought a new OEM pump. But now after installing it, I still see 36-38psi.

Obviously, something else is going on here. Battery is full, so that shouldn’t be a factor. I’m pretty experienced at working on gas and diesel engines, outboards too. But no experience working on a Rotax. I considered buying a BUDS. But considering the cost for the device and license, I’d rather not. Anyone have any ideas?
 
since you have the 250hp, I assume you have the external intercooler. at least in the older seadoo's they could start leaking and cause symptoms similar to what you're describing. just disconnect and remove the intercooler, if there is any water in there, that's you're issue. you could also pressure test the intercooler to confirm.
 
I pulled the outlet hose off the intercooler, and it’s all dry.

I also checked the voltage at the fuel pump plug, it’s 12.7 volts. So I’m still wondering why my fuel pressure is 20 psi low with 2 different pumps?
 
i don't know enough about fuel pumps and pressure to offer you assistance, hopefully someone more knowledgeable than me will chime in. you mentioned you moved the plugs and wires around, did you try replacing the plugs with new ones? these motors are pretty sensitive to spark plugs and might be a cheap option to try.
 
Back
Top