1998 150 CARB. V-MAX LOSS OF POWER

[MITCH WELCH]

Outboard: 1998 carb. 150 VMAX. Problem: Engine starts and runs fine for about 8-12 miles and than it will surge a couple of times and back down from 5900 RPM's to 5100 RPM's. It seems to run fine at 5100 RPM's (after those couple initial surges), but will not climb back to 5900 RPM's for the rest of the fishing day. So far, these same symptoms have happend like clockwork on the last 4 fishing trips. My mechanic has replaced the stator trigger and key switch. Also, he's checked the compression, plugs, and gas. I've cleaned the filter and replaced the plugs. He said the engine computer would be the next step ($1000.) I've already put about $500. into trying to find the problem. Another $1000. would be pretty expensive, especially if it does not work. Any ideas or suggestions would be greatly appreciated. Thanks.

 

[12Footer]

Re: 1998 150 CARB. V-MAX LOSS OF POWER

It only does this when something gets warmed-up good? It souinds like a coil, but it could be tank not venting,fuel pump,or debris in a carb. Does it run hotter than normal, or have a noticeable miss when this symptom occurs? Does the primer bulb collapse?

 

[manowar]

Re: 1998 150 CARB. V-MAX LOSS OF POWER

I know its along shot but are you mixing oil and fuel correctly other wise i agree with 12footer

 

[MITCH WELCH]

Re: 1998 150 CARB. V-MAX LOSS OF POWER

12Footer - Do not know if engine is running hotter than normal (warning buzzer does not come on). Yes engine does surge (or miss) when symptoms occur. I'll be running down the lake just fine at 5900 RPM's and all the sudded the outboard will surge a couple of times and RPM's will reduce to 5100 RPM's. It'll stay that way for the rest of the day, but on the next trip she'll run fine for 8-12 miles and than the same thing happens again. Do not know if primer bulb is collapsed or not. I'll check out your suggestions. If you come up with any other ideas - please let me know. I'm taking the boat back to the mechanic Monday. Does it sound like it could need a new computer? Thanks. Also, manowar - as far as I can tell the gas/oil ratio is correct. Thanks 12Footer and manowar.

 

[petryshyn]

Re: 1998 150 CARB. V-MAX LOSS OF POWER

I like 12footer's idea about the coils. How does it idle once the loss of power occurs?

 

[MITCH WELCH]

Re: 1998 150 CARB. V-MAX LOSS OF POWER

Petryshyn - the engine idles fine. Once the engine has made a couple of initial surges and backs down to 5100 RPM's everything is fine except she will not get back to 5900 the rest of the day. If someone did'nt know better they'd think that's the way the engine is suppose to run. 12Footer had some excellent ideas, but I'm still looking for more if anyone can think of anything else. Thanks petryshyn.

 

[petryshyn]

Re: 1998 150 CARB. V-MAX LOSS OF POWER

If it idles good, I'd put it in gear and very slowly, slowly, slowly accelerate. If one cylinder is dropping out under load only, you should feel drop out at this time. Coils and High tension wires will do that.<br />I not familiar with this engine. Does it have an electronic advance, or still the conventional moveable pickup coil? Before I'd purchase a computer, I'd visit my local electronics shop and buy a can of freeze spray. (if you can't find freeze spray, an ice pack will work)When the drop in HP occurs, pop the hood and cool down the computer with the spray.(empty the whole darn can on it) If this rectifies the problem, you'll know what to do. . .

 

[MITCH WELCH]

Re: 1998 150 CARB. V-MAX LOSS OF POWER

Thanks everyone for the great suggestions. There is still time for more..... I'm going to have each of the ones already mentioned checked out on Monday. If anyone else comes up with anything between now and Sunday night please don't hesitate to throw them in the mix. Once again, thanks for the help!

 

[MITCH WELCH]

Re: 1998 150 CARB. V-MAX LOSS OF POWER

Boat went to the mechanic yesterday. He feels the bottom carberator is blocked somewhere in the jets. He blew it out with air. I went to the lake to test run it. It still does not run right. The symptoms changed a little. It ran for about 8 miles great, than it started surging and backed down from 5900 RPM's to 5100 again. This time it just kept surging between 5100 and 5200 (possibly a partial block vice a complete block?). Before it just surged a couple of times and would not go above 5100, but did not surge anymore. Mechanic feels there could be trash getting picked up around the float ball? I'm taking it back tomorrow and he's going to soak it for a day and we'll try it again. Anyone got any ideas on how to get the trash out (if that's the problem). If this does not work I'll have to by a new carb. At least we're of the computer now. Help?

 

[petryshyn]

Re: 1998 150 CARB. V-MAX LOSS OF POWER

can't see having to buy a new carb.....if in fact the carb is getting plugged, install a fine fuel filter in line till the grime is purged (little skeptical though...)will this engine derate if overheating?<br />

Happy boating!!

 

[MITCH WELCH]

Re: 1998 150 CARB. V-MAX LOSS OF POWER

schematic, what do you mean by derate? Have not had a problem with the engine overheating on the lake. I'm not sure which # plug was not firing when the mechanic tested it. It was the bottom, left, plug. When he unplugged the other plug wires on the left side of the engine the plug did fire (I guess it was just to weak to tell when all plugs wires were attached). Once he switched off carb's the bottom left plug fired like it was suppose to. He then blew the carb. out with air and re-attached it to its orginal location and the plug fired. Assumed problem was fixed and took it for test ride (read symptoms above). Of course the original symptoms came back or I assume it's the original symptoms since engine started surging again. Thanks schematic.

 

[OBMD]

Re: 1998 150 CARB. V-MAX LOSS OF POWER

Have your mechanic do the Yamaha flowtest on the carb.If he does not know about the flowtest, then have him call his RTA's at Yamaha Service. Debris is stuck behind the inlet needle seat. It is not removable, so tech will have to back blow untl debris is removed.

 

[rlouns]

Re: 1998 150 CARB. V-MAX LOSS OF POWER

I would also check the wires going to the coils or coming from the pick-up. I had one going to my #2 coil breaking down (it was actually the wire breaking in to) and I did not find it until the wire came out of the rubber boot at the connector where it had broken.

 

[Dunk]

Re: 1998 150 CARB. V-MAX LOSS OF POWER

Has anyone checked the Rev Limiter on that engine. 5900 sounds little on the wild side for that carbed yam 150. They are rated at 5500 max and put out their best power at 52-5300. I've never seen one live very long running them over 5500.<br /><br /> If it's not the rev limiter trying to kick in then I'd be worried about lean condition existing at those high rpms. The jets are only so big and made to fead the engine at the rated rpms. At 5900 she's pulling more air than the jets can supply fuel. Leaned out like that she could be running too hot of combustion chamber temps. That surging could very well be preignition from heat and carbon. If you haven't been staying up with using a carbon remover the rings may be carboned up and not disapating heat. This causes them to swell and grab the cylinder walls. Running lean out on top of this will destroy the engine in short order.<br /><br /> I would get another prop with 2" more pitch and bring that engine down into it's right rpm range. Even before that I''d run healthy dose of Seafoam or Merc Power Tune through her, both are excellent carbon removers. I'd do this even if you've been running Yam's ring free on a steady diet.

 

[MITCH WELCH]

Re: 1998 150 CARB. V-MAX LOSS OF POWER

OBMD - Mechanic did the flowtest on the carb. He said it appears some trash is stuck in the carb., but he can't get it out. He let it soak in carb. cleaner all day and back blew it, but no luck. It looks like I'm stuck buying a new carb. Would you recommend a new or used one? I can get a used one for half the price.<br />DUNK - I know the book says the 150 carb. V-Max is designed to run at 5500, but he dealer I bought the boat engine from said 5900 was fine for that specific engine. Also, I have a friend with the same exact moter that also runs 5900 - 6000. Additionally, my mechanic says 5900 fine? Now you've got me confused - I don't know what to think. Anyone else got any input into the correct RPM range for the engine? I use a 25" pitch yamaha prop on a 185ZX Skeeter.