Engine high speed RPM problem

Note: This site contains eBay affiliate links for which SeaDooForum.com may be compensated
Status
Not open for further replies.
fzandome

fzandome

Active Member
Have not been here a while as the boat was working great until this first trip of the year. Boat work great first couple of days then, at around 4500 RPM, the left engine started hunting between 3500 and 4500 RPM. Went back to the dock, off loaded the pacs and took it out on a test run, it worked fine. The next time out, at around 7000 RPM on the right engine, the left engine did not want to go to full RPM, (stayed around 6500) and started hunting again, about a 2000 RPM spread this time, then finally died. I was able to start it back up and same situation about 4-5 times. Eng worked fine at a "no wake" speed. Scratch my head, had a beer, and went out again. This time, again all was well. Going on a two week lake vacation in july and would like to have this resolved before I go. Intermittent problems are such a PITA, especially when you have bored little ones, if you know what I mean Thoughts.....
 
Unplug the rectifier the next time it happens. If it clears up, replace it.


Repairing and selling iPads, iPhones and Mini iPads.
 
Yep... if you have a bad regulator... the whacky voltage can play havoc on the ignition unit.


BUT.... since one engine is OK... I'm going to assume that your carbs need some love. AND... if that's the case... don't keep running the boat. Running a 2-stroke lean will be the death of the engine.
 
I thought it might be a carb problem initially, Since time is of essence, I'm ordering a rectifier and maybe a couple of carb kits unless I can find somebody to do them for me. Does anybody out there still do these things (carbs)? Can ship overnight. Edit.... decided to buy the kits and do it myself... Wish me luck
 
Last edited by a moderator:
I'm having about the same problem except on mine I also have a hard start on the starboard side. Had the carbs cleaned 2 yrs ago but, a mechanic told me a carb can go bad within 6 months after cleaning if the lines have not been changed or the ethanol in the gas.
The hard start could be my rotary valve. Good luck because I know exactly what your going through.
 
Have a potential problem with the boat. I remove the left carbs and noticed one of the 2mm small oil lines was broken off the rear. I'm assuming this happen a while ago. What am I look at here. Last time I ran the boat all seem OK except for the RPM hunting on this engine. Question is what do these small lines feed to what can I expect to repair.comments.
 
Last edited by a moderator:
Oh no, that's your oil injector line! Basically, you were running that carb and intake on straight fuel with no oil going to the motor.

It will require teardown and inspection to determine the extent of damage, what's left for compression after that happened?
 
Are these the oil injectors.... darn looks like a compression check tomorrow. expensive carb job if there is a problem. Hopefully it broke when I was poking around down there.. We will see
 
Last edited by a moderator:
fzandome said:
No it's not the main oil injector line... much much smaller.. about 1/8 inch.About 6 inches long. There are two going into two different directions. Only can see them when the carbs are out. They were brittle. Are these the oil injectors....
Click to expand...

Standby, I have the carbs off of my boat with the intakes exposed showing the oil injector lines and nozzles I will go and take a picture of that for you.
 
Ok, here's a picture of my intakes with the carbs off that show the brass oil injectors just inside the intakes and if you look closely you will see the outside of the injector body with the tiny oil line attached to it that runs down and over to the pump (both painted white)
Injector lines.jpg
 
Just did a compression test. Registering 150 psi.... the line must have broke when I was taking the carb out. Thank God. Would have ticked me off spending all that money on those carb kits and having to deal with an an engine problem. Boat is to old for that kind of expense. However I think all lines should be replace soon. Old boats cheap... repairing old boats expense.
 
fzandome said:
Just did a compression test. Registering 150 psi.... the line must have broke when I was taking the carb out. Thank God. Would have ticked me off spending all that money on those carb kits and having to deal with an an engine problem. Boat is to old for that kind of expense. However I think all lines should be replace soon. Old boats cheap... repairing old boats expense.
Click to expand...

Oh that's good news I'm happy your motor wasn't damaged on account of that line! I'm going to go ahead and replace those oil lines on mine while it's that far apart, I'm installing a Mercury spin on style fuel / water separator filter on the main line and have all new fuel lines installed so hopefully I won't have to get back into that area for a few years or more now.
 
Where did you get the fuel lines. There is a smash of them. Have to buy it by the yard to do the whole boat
 
I bought mine locally from an O'Reilly Auto parts store they sell fuel injection grade alcohol resistant line in 25' rolls, also got two feet of the 1/4" line for the carbs. By the time I ran all the lines to the selector switch and back I used a good bit of that roll up.
 
Yep, sounds like a fuel system issue, and be sure those rubber oil lines aren't broken, they do rot over a period of time. 3/32 ID tygon F-4040-A is the stuff you want for those oil lines.

Good idea, installing a Mercury style spin on fuel/water separator. Those things are the very best solution available for stopping any trash from moving into your pump and carbs.
 
Since I'm on a deadline to get the carbs in, I think I'll replace the lines, both fuel and oil to the first connectors off the carbs. That way I don't need to get "in there" for the replacement... I do have a question on the oil tank, The oil sensor grommet is leaking and I don't see any grommets in the parts listings for that. Any "fixes". I just keep the level low. When you really get to looking at those lines, there is a lot of them, especially for the two eng boats...

If the oil lines are 3/8 inch, what size are the fuel.
 
I think those oil lines may be 5/16 instead of 3/8 but don't quote me on that. The small rubber lines from the oil pump are the 3/32 id Tygon mentioned above. They're actually metric, and 3/8" may be too large. I believe the fuel lines should be 1/4", some fuel lines on my 951 boat are 5/16", I have both sizes on there.

Those oil tank grommets are available, not sure from where. I'm not sure if mine leaks or not, keep less than 1/2 tank of oil in tank in case a leak develops, don't want to open the bilge and find $80 of contaminated oil pooled up and about to be sucked out to sea.

While you're in there doing this work don't forget to pay attention to the oil pump cable adjustment, the lever needs to be in the correct position at idle position, so after all cable adjustments are complete then last thing go back and double check the oil pump cable adjustment, I check/adjust the oil pump control cable before initial startup and again after final idle adjustment.
 
I want to add for clarification, I think you will find the larger oil tank lines are 5/16" id and IMO it's not necessary to use Tygon F-4040-A for those, a clear vinyl tubing from the likes of Home Depot should be sufficient and should last a good while. I would use the Tygon for the small 3/32 id lines.

I could be completely wrong on some of this, just sharing what I think I know. The 3/8" id tubing is not found anywhere on my boat, the 5/16 id tubing is what I recall using. And the smaller fuel lines I used were 1/4" id, but my boat has the 951 motor, so I'm assuming BRP used those same size id's on the others (impossible to locate metric, sizes to be exact).

Don't ask me why we cannot easily locate metric size tubing these days, life's puzzles are never ending.
 
Ok having a problem. rebuilt and installed the first set of carbs and it started about three times. and then it would not start any more. Thinking i screwed something up, I disconnect the inlet fuel line and turned over the engine and no fuel. the manual does not address this at all. I don't see a fuel pump so what drives the fuel. Now I thinking this was the original problem.... Help please as I don't want to rip out the carbs again to verify I put them together correctly.... I was VERY carful when I did them.. One at a time, everything laid out (parts)as it come apart. Pop check etc. By the way, this job sucks, especially for a old stiff guy.

Edit

Noticed there was no fuel in the fuel filter.

Other question. Since the other Rt hand carb is out and the lines unplugged is this a problem.. are they interconnected somehow.

Also notice with I sucked on the inlet fuel line, there was no fuel and no resistance. Does the other carb lines need to be blocked or installed on the carburetor.

This must had fuel initially to start but is not being feed with it now...
 
Last edited by a moderator:
fzandome said:
Other question. Since the other Rt hand carb is out and the lines unplugged is this a problem.. are they interconnected somehow.

Also notice with I sucked on the inlet fuel line, there was no fuel and no resistance. Does the other carb lines need to be blocked or installed on the carburetor.

This must had fuel initially to start but is not being feed with it now...
Click to expand...

Yes, many of these are equipped with the fuel pump mounted on the carb so if yours is this way it certainly can't draw fuel out of the fuel tank if you cannot either.

My opinion is you need to block off that other fuel line, you're probably sucking air from there! Remove your fuel tank gas cap and blow into the fuel line to find out where the air is going, you should hear a gurgling sound in the bottom of your fuel tank as the air is forced up through the fuel pickup similar to a fish tank.
 
Also, don't forget to confirm the oil injection pump lever adjustment is made correctly, a rough adjustment to get it in the ball park and then final check once the idle speed adjustments are set up where you want them.
 
Just in case check your fuel selector valve by the helm that's always an out of sight out of mind possibility but those two selectors should isolate the off /main / reserve draw for each engine as they each have their own.

Check the fuel tank vent line make sure it's not pinched and don't be afraid to take that selector valve out of the boat and make sure it's still flowing fuel through the ports they are known to fail and be obstructed.
 
Last edited by a moderator:
Took the carb out and verified it was put together correctly by using the other carb as a model... All was OK. Also found a fuel pump check in the manual. Blowing and sucking various inlet/outlet lines and it was OK per the manual.. Have both carbs rebuilt now and will put both in in tomorrow. If I still have a fuel flow problem, I'll let you know for more guidance. If the fuel flows with both carbs in, that means they are interconnect some how... although I don't see that in the fuel schematic. wish me luck
 
Status
Not open for further replies.

Similar threads

Ploppy69
1997 Seadoo XP High RPM-but struggles to plane out.
Replies
1
Views
64
tobytd
tobytd
H
1997 Seadoo Challenger 1800 (787s)- Dies Midrange
Replies
2
Views
402
Hunter77ah
H
C
2008 RXT-X rpm bouncing/performance issue
Replies
3
Views
325
cbn70
C
P
Sportster Le Di RPM loss with ANY left steering.
Replies
0
Views
335
PSBeachBum
P
T
Something jammed and bogging engine - need help!
Replies
1
Views
304
etemplet
etemplet
Back
Top