4hp Nissan OB Won't Start

[foggysail]

Another thing to consider if you don't already have enough. The size of your engine leads me to believe it has an attached fuel tank. Floating around in that tank is a fuel filter which if dirty will prevent fuel from ever getting into the combustion chamber.

Another place to look for a filter if you can get at it is attached to the fuel line somewhere between the proper and the carburetor.

[SV Sea Monkey]

Thank you all for the continued input. Here's my plan for the weekend:

1. Confirm the carb is (still) the (only) problem by checking fuel flow to the carb (pull the fuel line off and look) and to the cylinder (check if spark plug is wet after trying to start).
2. Rule out other problems by trying raw fuel in the cylinder or using starter fluid (perchance: why no starting fluid?). If this doesn't work, I'll see if I can borrow a compression tester and spark tester from the local auto parts store. I have tried the "farmer's check" for both and have a visible spark and my thumb blows off the hole.
3. Assuming it is a carb problem (and only a carb problem), I'll try cleaning/soaking again (and find the hidden third jet), then reassembly with a carb rebuild kit. Aviation fuel is an option but a bit harder for me to get. I think a have some old guitar strings around here somewhere, and I'll try to get a rebuild kit before the weekend.
4. Once I get it running, clean all fuel filters and change the oil, particularly if I use aviation fuel.

I am learning a lot about this outboard (all time well spent), but I suspect I may want to upgrade to a larger outboard next year anyway--so I'm trying to minimize effort and expense on this one. We have a 10' AB RIB (hypalon with double fiberglass floor--got a great deal on Craig's List), and our plans include cruising the U.S. east coast for one year, leaving next summer. I'll be happy with the small OB if I can coax the dinghy onto a plane in flat water with 3 people on board. If not, I'll want to upgrade anyway. Will the 4hp push the dinghy onto a plane? I've heard that I may be able to upgrade the carb and get to 6hp--not sure if that's true or if even that would be enough. If I'm going to upgrade the carb, now would be the time.

By the way, I owe you all a beer at the SSCA Gam or the boat show in Annapolis. Anyone planning on being there?

[Paul L]

You're asking too much of those 4 horses. It will not plane a rib like you have and 3 people. My 9.8 won't handle 3 people on a plane.

[SV Sea Monkey]

Originally Posted by Paul L

You're asking too much of those 4 horses. It will not plane a rib like you have and 3 people. My 9.8 won't handle 3 people on a plane.

I was afraid of that. I recall 20 years ago that a 9.9 would plane two of us with dive gear, or three in really flat water--but that was on a slightly smaller, lighter boat. I was hoping someone would tell me that these new-tangled 4-stroke outboards could do magic. Sounds like converting to 6 (if that's even possible) won't cut it either, even with anti-cavitation "wings". So now I need to decide how much time/money to put into this one before selling it. Anyone want a non-working Nissan 4hp 4-stroke outboard?

[foggysail]

Originally Posted by Paul L

You're asking too much of those 4 horses. It will not plane a rib like you have and 3 people. My 9.8 won't handle 3 people on a plane.

I agree although I though his problem is that he cannot get the engine to start?????

[Therapy]

Originally Posted by SV Sea Monkey

Anyone want a non-working Nissan 4hp 4-stroke outboard?

I'll take it. It will be perfect for my Gheenoe.

Just give it to someone in November that is headed south and I will pick it up anywhere in east, central FL whenever they get there.

[MarkSF]

All the carb parts, including jets, are available here :

2003 M4C Tohatsu Outboard CARBURETOR Diagram and Parts

or you could just change the entire carb, for $172.

[MarkSF]

Make sure your rebuild includes checking, or replacing, the fuel pump diaphragms - 26 and 27 in the above diagram.

[SV Sea Monkey]

Originally Posted by foggysail

I agree although I though his problem is that he cannot get the engine to start?????

Yes, my original post was asking for advice on getting the engine started. I wanted to get it started so I could see if it was adequate for the dinghy (it sounds like it won't be). I'm hesitant to put a lot more effort or money into it since I'll probably sell it anyway and get a larger one--but this one will be worth a lot more working than broken. At this point I'm still planning to follow all the good advice I got here, but meanwhile I will be on the lookout for a good deal on a larger outboard. I'll also prioritize other projects ahead of the outboard for now.

So at this point I have a non-working 4hp outboard that I can continue to work on as time allows, a good 10' RIB with oars, and an 8' zodiac PVC inflatable that's still in good shape but just wasn't big enough. I'm planning to sell the smaller inflatable and the 4hp outboard, but I'll try to get the outboard working first. I'll start another thread in Classifieds in case anyone wants to make an offer.

Thank you to everyone who chimed in on this thread with helpful advice. I'll let you know if/when I get it running.

[SV Sea Monkey]

Got it working. Thanks to all for the advice. I went ahead and ordered the 6hp carb instead of messing around with the 4hp. The new carb, fresh gas, and about 30 pulls did it. Now it starts on one pull and gets me on a plane in flat water easily. I have yet to try it with the rest of the crew, but we'll stick with this one for a while, at least. When we make it down south and want to do some distant snorkeling we may consider a larger outboard.