Pontoon Boat & Deck Boat Forum

Recently bought a pontoon that has a 90hp Mercury 6 cylinder motor on it. It is a older motor. This thing will not hardly start for nothing. When it does start it does not want to idle most of the time and when you try to go in reverse it dies. Will post pics of the controls of the motor and the engine. Well today went to load it up and pull it home from the water and it backfired trying to start it and then it caught on fire. By the grace of god we had sense enough to react and there was no damage that we can find inside the engine except the very bottom gas line. We think it was cracked and leaking and that was the cause. We could see a dribble of gas ever now and then in the water from the bottom area of engine. There is a few scorched wires but nothing melted and the wires are just minor surface scorch. Now the question is can I just take water hose and spray the fire extinguisher gunk off of the inside of the engine without the water damaging anything and just let it air dry for a day or two before I hook the ear muffs and try to see what its problem is. Could it have been the gas line sucking air causing it not to run correctly? Sorry for the long story but trying to get some advice. No one around here wants to work on it since it is a Mercury. Told me I would be better off just putting a different engine on it.

Leaking gas line could of been the problem. If it was sucking air that would cause the engine not to run

Thank you. Now can I just spray water into the engine area to remove the fire extinguisher residue? Not pressure wash or any pressure like that. Just normal garden hose pressure. Should it be fine as long as I make sure it does not get into the carbs? Please reply soon.

If this was a dry chemical extinguisher you should have rinsed it off as soon as possible so it doesn't destroy (corrode) every electrical thing it touches. When you say "inside the engine" I assume you mean under the cover. Just put some sandwich bags or something over the carb intake to keep water out. Next, don't even try to start that motor until you replace the fuel line you saw and then check/ replace on the rest of the fuel lines. Also get yourself a new fuel pump (look on Amazon.com) as that may also be your starting/running problem. They are not expensive and not hard to change. Also, since it sounds like you don't know a lot about the motor, I recommend replacing the water pump unless you know for a fact that it was recently changed.
Hope this helps.

Thanks so much. We have replaced the fuel line and I have blowed majority of the dry chemical stuff out from it with air but some is still there. We were blessed. Can not find any damage at all to anything in the engine area except a few scorched wires. You are correct. We know nothing about the motor except it ran fine when the previous owner shown us before it was bought 2 weeks ago. Maybe he had it doctored up to run just to sell. You know there is people out there that will tell you anything! Thanks again for your advice, It is greatly appreciated!

The serial number to the engine is A936319
I have looked everywhere online and I cant seem to find rebuild kits for the carbs. Can anyone lead me to them? It will be greatly appreciated!

One last question if anyone knows, Does my carb setup suppose to have the 3 shutter choke assembly. I have attached a pic. Not great, the best I could do. The break down online of this motor does not show it as a part to be ordered if needed. Someone told me it should have that or a breather over the carbs. Please someone let me know if you know.

Certainly not saying this fine group can't help, but here is another source for help.

Outboard Troubleshooter group on Facebook.
https://www.facebook.com/groups/682633021881857/

They're a closed group, but let me in! I've noticed threads on older, smaller horsepower engines.

Good luck.

On older 2 stroke engines, the best thing anyone can do if it's running erratically is (1) change the spark plugs, (2) change the fuel filters, (3) change the fuel line if it's suspected to be old and (4) change the fuel pump rubber membrane. 90/10 gasoline is really tough on old motors, so you want to make sure your fuel is completely fresh--preferably 100% gasoline.

The carbs. usually don't require a full carb. kit. Most of them are just dirty and can be cleaned by disassembling and spraying with carb. cleaner. If you tear any gaskets, the kit would be needed.

I have one of the first Yamaha 115 hp V-4's, and I can remove, clean, reassemble and reinstall the carbs. in 1 hour flat. Not much of a job, really.

Before I would invest my time or money on an old motor I'd check where the cylinder compression is at on all cylinders. Just because it ran great before you bought does not mean a thing with an old motor...

teecro wrote:Before I would invest my time or money on an old motor I'd check where the cylinder compression is at on all cylinders. Just because it ran great before you bought does not mean a thing with an old motor...

...and that is some EXCELLENT advice.

RonKMiller wrote:

teecro wrote:Before I would invest my time or money on an old motor I'd check where the cylinder compression is at on all cylinders. Just because it ran great before you bought does not mean a thing with an old motor...

...and that is some EXCELLENT advice.

LoL yes it is... My Father was a Crew Chief in the USAF and he used to comment on the complexities of the B29 Radial engines. Engines that ran fine up to the point of being shutdown would have to be removed at on the next ignition as they would have something vital wrong with them...

Got the engine all cleaned up and replaced the fuel line and plugs and it seems to be better at starting but it still does not want to stay running at idle. Will try and check compression. About done with it. There is not much more to do. Oh well.

evartsboy73 wrote:Got the engine all cleaned up and replaced the fuel line and plugs and it seems to be better at starting but it still does not want to stay running at idle. Will try and check compression. About done with it. There is not much more to do. Oh well.

If it was running fine before you bought it weeks ago what has changed since then? Could you have added some dirty fuel, gotten the fuel/oil mixture wrong, plugged fuel filter, fuel pump or otherwise restricted fuel system? Since you know nothing of its history get a compression reading so your not chasing strays when the problem could be loss of compression.