Yamaha 150 vmax Carb Problems

[nicswet7]

Hi there

I wonder if someone on here can help.

I have a 1998 150 vmax carburettor and have had a couple of problems.

I was out on Tuesday morning and noticed the engine was running very rough between around 800 to 1400 rpms. I suspected that there may have been some dirt/gum in carbs from the winter storage period so sprayed some cleaner into them to try to sort that out. I then went to take the boat for a run to try to clear them through. I brought the boat up onto the plane and ran for a little while at around 4-5000 rpms and it went well. It was still rough around 800 to 1400 rpms but as soon as i was over the 1400rpms it seemed to run as normal. However as we came off the plane the engine died. I could restart it but I didn’t have sufficient power to put it in gear and keep it running. I then took it into the local marine mechanic yesterday morning who took the carbs off and cleaned them through. This seemed to resolve the issue however he was concerned that there may be a further electrical problem. I would also add that I have a Yamaha 10 micron fuel filter installed and I replaced the element around 3 weeks ago.

The boat ran fine for most of yesterday and we went out for a little evening cruise. After around an hour, I dropped the other guys off at the pontoon. When I came to restart the boat to take it back to my mooring there was nothing – the engine wouldn’t start, tilt and there were no gauges. It was as if everything was dead. I have had this problem once before and found it to be the 20A fuse blown on the port side of the engine so I immediately changed this fuse but this didn't solve the problem. I also went through all of the other fuses but this didn’t resolve the problem - there was still nothing. During this time the other electrics on the boat all worked fine however – sounder, nav lights and bilge pump so presumed it couldn’t be the battery. About 30 mins later after moving the boat to a temporary dock with our tender I tried the key and the engine started, tilted and all gauges worked and the engine ran fine.

I’m wondering whether anybody has any ideas on what this could be? Could something be overheating?

Thank you in advance for your help

Nic

[rodbolt17]

sounds like a battery cable/connection problem.

[nicswet7]

Thanks for your reply. I have just cleaned all the contacts and the engine seems to be back to normal. I was worried one of the components on the engine may be faulty. Could it be a bad regulator or Cdi unit? Would there be any other signs if this was the case?

[TownsendsFJR1300]

I can't speak abbout the CDI, BUT if your going to let the engine sit for more than a month, I would strongly suggest running a fuel stabilizer (Seafoam) or Yamaha now makes a stabilizer too, on a REGULAR BASIS.

Yamaha "Ringfree" is an excellent fuel additive that cleans the top end of 2 and 4 strokes (kinda expensive but worth it). Its much cheaper in the end vs paying a mechainic, getting stuck, towed, etc.

Fuel breaks down very quickly (especially with ethonol) and will varnish up your carbs VERY quickly, even if you run the engine dry (some fuel remains in the bowl and gums up especially the low speed jets((very, very small orifices)).

[nicswet7]

Thanks for your reply. I have been using star tron in the fuel for the last 2 years as it had read good reviews. Would you say that ring free is better?

I don't know whether anyone else would be able comment on the electric issue? Does the fact that it is now back running ok point to a bad connection rather than any other component failure?

[rodbolt17]

get bad CDI units or ign coils out of your head.
just quit.

[TownsendsFJR1300]

Thanks for your reply. I have been using star tron in the fuel for the last 2 years as it had read good reviews. Would you say that ring free is better?

I don't know whether anyone else would be able comment on the electric issue? Does the fact that it is now back running ok point to a bad connection rather than any other component failure?

I'm not familiar with Startron BUT if you had to have the carbs cleaned while using it, IMHO, it's NOT WORKING. The yamaha Ringfree is NOT a fuel STABILIZER but a cleaner.


I have had good results with "Gas Shok" for a stabilizer but currently use "K100MG" as I have a 50 gallon built in tank, the tank is close to 20 years old and I was getting some moisture (from time) in the tank. The K100 is not cheap but does indeed work extremly well (especiaslly for large built in tanks). I state this as when mixed with fuel and water, it literally keeps the MIX together (the water DOES NOT SEPARATE) and is eventually burned off. Since using that and NON ethonol fuel, my fuel is now super clear/fresh. I know Startron cannot do the above (my local MC shop showed me several different mixes including Startron, water separated as well).

I use K100MG: K100 Fuel Treatment A little goes a long way. With such a large tank and a fuel sipping F150, I can run an entire day on 5 gallons. I bought a case of 4 several years ago and still have a full bottle and a half left.

As for the electrics, if you found corrosion/loose connections (cleaned/tighened) and its running fine, I wouldn't read anything more into it and just run it, your likely ok. If it acts up, go from there.

If you don't go with K100 or Seafoam, go with something else but Startron (unless you like keeping your mechanic busy). As stated earlier, Yamaha supposedly came out with their own stabilizer (supposed to be somewhat Yamaha expensive) but I've found their products to actually work...

Good luck and please post your results..

[nicswet7]

Great thanks again for all your posts. I think I've narrowed down the electrical problem to a bad isolator switch - didn't think these things could be an issue but apparently moisture can get inside them. It's the original perko model so is now 15 years old. I'll have to look into a better model switch.

I will look into the fuel treatment and see your point re the star tron. I'm based in the uk so finding k100 may be struggle so will try the ring free. I'm convinced having read your posts and having done some research that it was an issue with the low speed jet.

[TownsendsFJR1300]

Great thanks again for all your posts. I think I've narrowed down the electrical problem to a bad isolator switch - didn't think these things could be an issue but apparently moisture can get inside them. It's the original perko model so is now 15 years old. I'll have to look into a better model switch.

I will look into the fuel treatment and see your point re the star tron. I'm based in the uk so finding k100 may be struggle so will try the ring free. I'm convinced having read your posts and having done some research that it was an issue with the low speed jet.

Yep, any switchable contacts, especially in the marine enviroment can turn green and corrode, especially over time. That switch served its purpose for 15 years.