Bogging at High Speed

[oregonfish]

I've used the search on this topic about a thousand times. Lots of people with similar problems, but nobody ever posts the fix.<br />I've got a 1985 Mariner 40hp (Yamaha) SN 40EL 420664. The thing runs like a champ...Until a couple of weeks ago. After a few hours of fishing, I was heading back to the dock for the day. I opened it up to get back. Just after hitting top RPM's it started bogging down and choking out as if it were running out of gas. If I rev'd it up using the throttle only, it would run fine for another 60-90 seconds. Took the cowling off, and that made no difference. Pumped the primer ball, and that made no difference either. <br />Went home and got a can of Deep Creep and did the cylanders (couldn't figure out how to get at the carb throats). Checked compression; good at 120 x2. Took the fuel pump off. While doing this, I noticed that one of the two bolts holding the pump to the powerhead was not very tight. I thought this might be it. Other than that, the pump looked to be in good shape. No holes or tears in the diaphragms and check valves worked great. <br />Looked at the manual and figured out how to Deep Creep the carbs. Took it back out to the lake, and sprayed away. Let it sit for half an hour, and started it up. Got a good amount of smoke and then she took off fine. After this, I changed the plugs for good measure. <br />Worked for the rest of that night and all of the next(another three hours). Then last night, it worked for the first two hours at all speed ranges. After stopping for about 40 minutes to pull out some prize crappie, I took of for the dock again and, wham! Same thing. I sprayed some more Deep Creep into the carbs and it smoked the place up a bit and then ran fine for the next 5 min at WOT. By then it was dark. <br />So, it has no pattern, other than it usually starts at WOT. It does it hot or cold. Day or Night. <br />PLEASE HELP!!!!!!!

 

[oregonfish]

Re: Bogging at High Speed

Forgot to mention, I've also changed the ball and hose, and yes, the tank is vented!

 

[LubeDude]

Re: Bogging at High Speed

when was the last time you changed the impeller?<br /><br />The engine will act like that if it starts to overheat, as the pistons will expand and it will start to drag down.

 

[oregonfish]

Re: Bogging at High Speed

LubeDude, thanks for the response.<br />The boat is new to me as of last October. I have to order the impeller as the shops in my area want to charge twice as much as the online shops do for less parts. The wierd part is that it seems to do it if I've been running for 5 minutes or if it's been running for 3 hrs. Does this line up with the impeller? Also, it will still run at low RPM's fine.

 

[Vlad D Impeller]

Re: Bogging at High Speed

Try taking the carbs off and cleaning them, i suspect that a small bit of dirt is the culprit there.

 

[oregonfish]

Re: Bogging at High Speed

Carbs even after 2 doses of deep creep???

 

[oregonfish]

Re: Bogging at High Speed

Any other possibilities? Anyone?

 

[roscoe]

Re: Bogging at High Speed

Deep Creep and other solvents will not clean out chunks of rust or other debris that can not be disolved. Also, spraying thru the carb throat will not get into the carb internals. <br /><br />Its kind of like pouring a bucket of water into the basement floor drain in an effort to flush out a sink drain on the second floor.<br /><br />Hurrry, the crappies are waiting.

 

[horsefly38425]

Re: Bogging at High Speed

checked for anything in tank /or water in carb bowl if it pi-ser works imp. is ok

 

[LubeDude]

Re: Bogging at High Speed

Rosco is correct, you have to take them apart to really clean them.<br /><br />Say, what part of southern ORYGUN are you located? Im over by CoosBay. Lakeside, Ten Mile Lakes.

 

[oregonfish]

Re: Bogging at High Speed

I don't want to hear that carb talk!!! It took all of my courage to pull the lower unit and check the condition of the impeller.LOL Is a carb cleaning a tough job? I'm willing to give it a go, I just don't want to screw anything up! And it's hard to commit to doing it when I took it out again last night and it worked great! <br /><br />LubeDude, I'm in Ashland. Right on the California border. <br /><br />Thanks for the replys. Let me know if you all think a rookie should tear up the carbs!

 

[oregonfish]

Re: Bogging at High Speed

Had another thought: The top carb has no throttle stop screw. Should both carbs have this screw even though they're linked? AND, would a rich throttle stop setting cause my problem? I've noticed a little fouling on the plugs a couple of times when it has done this.<br />Any help is welcome!!!

 

[tengals123]

Re: Bogging at High Speed

im in the process of doing my 3X carbs on my 68 merc. WOW!, yes it's a big job, but once into it you learn heaps about your motor.<br />cheers, BTW it may be heaps easier on your mariner.cheers

 

[oregonfish]

Re: Bogging at High Speed

Originally posted by oregonfish:<br /> Had another thought: The top carb has no throttle stop screw. Should both carbs have this screw even though they're linked? AND, would a rich throttle stop setting cause my problem? I've noticed a little fouling on the plugs a couple of times when it has done this.<br />Any help is welcome!!!

Any ideas?

 

[oregonfish]

Re: Bogging at High Speed

OK, maybe I found it. The spring that is attached to the electric choke was all bent and streatched. When I used the e-choke, the shutters never opened all the way(only about 1/3) If I used the knob, I could only get them to open all the way if I slammed the knob back in, which I never do on the water. I also noticed some gas leaking out of the carb throats around the silencer/flame arester. Could this be it. Weather's too nasty to go out and test it. Anybody want to make a guess?

 

[LubeDude]

Re: Bogging at High Speed

Originally posted by oregonfish:<br /> <br />LubeDude, I'm in Ashland. Right on the California border. <br /><br />

I have fished Imigrant Lake a couple of times, good Bass, and good sized crappy also.

 

[oregonfish]

Re: Bogging at High Speed

That is my spot! Been fishing there forever. Bass are hit and miss, but the crappie are always there.<br />Any ideas on my choke sticking? Could this cause flooding, fouling, and then bogging?

 

[oregonfish]

Re: Bogging at High Speed

Update!!!<br />OK, So you need the choke to open ALL the way in order to go w.o.t. Took it out on Monday, and it works better than it has since I got it. I almost wonder if the rpm's aren't too high now. I'm looking for a good used tach to stop guessing. <br />Thanks for all the help! I guess I learned alot throughout this process. Now I want to rebuild the carbs just to see if I can do it!