8-cyl outboard problems

Well here is what I have right now, and I will provide more info. when I get it later on.

My fire dept. had a boat donated to us from a bank, we live on the Ohio river so we need a good boat. The thing is, since we have had this boat we've put about $10,000 in it to rebuild the motor and a new paint job. Well the motor still isn't' running correctly. I will have to find out what all was done to it but I do know its still not right. I believe the boat is around 22'-24'. We had an electric fuel pump installed on it because the mechanic said it was starved of fuel. Well after still not running right for year, some of us decided to start messing with it ourselves because we've spent all of this money on a "free" boat. We recently change all the plugs and took the electric fuel pump of.

When trying to start the boat it smokes like crazy, and when it actually starts and you have the gas 3/4 throttle it will idle up really high then back down and back up again for about 20 minutes. We took it out when it started to run pretty good and after it kept taking off and slowing down (while the shifter was full throttle) it finally took off and we ran 41-43 for about 20 minutes. It started up fine if we shut it off but still wouldn't take off fine. One week later we took it out again and it ran like crap again do the same thing all ovre again.


Sorry I don't have all of the details yet but I am working on getting them. I was just wondering if I could get a few pointers to look into for now. We really can't afford to take to more mechanics with our budget.

Thanks.


Oh yeah, it also seems like it should be putting out a stonger stream of water when it actually runs. I'm guessing impellar but will that make it run bad? It is a steady stream coming out, but the other guy on the boat with me said his Johnson 70 has a stronger stream.

Re: 8-cyl outboard problems

Sounds like the carbs need a good bath and new kits. The V8s are great motors but if you treat them like a V6 you'll have nothing but problems. First you need to find a mechanic that's familiar with a V8 outboard.

The V8s came with an electric pump but it was a primer pump, not a constant run pump. Do not use a squeeze bulb on a V8. No 90* or bulkhead fittings. Nothing that is or can be a fuel restriction. 3/8" ID Marine fuel line only.

Use only Champion plugs and fresh 87 octane fuel.

The overboard stream will not be as strong as a 70 hp. They're different motors. Have your buddy bring his 70 in and park it beside the V8. You'll notice the difference.

We'll assume the carbs were cleaned and a complete water pump was installed when the motor was rebuilt. If not, do so now. When you order the carb kits (OE only) order 8 needle & seats for a crossflow and use them, not the needle & seat in the looper carb kit. Once you see the two side by side you'll see why.

Do not set it up like a V6. Depending on which model you have you'll target at least 6200 rpm. If you only turn it 5500, take it off and get a 200 or 225. No sense carring around all that weight if you aren't going to take advantage of the technology.

Do not - ever - run the motor under a load with the airbox cover off. Never.

Look at the set up. The AV plate must be at least 1/2" above the bottom. The actual correct location depends on the prop. Remember a 20" V8 is actually 23". A 25" model is actually 28".

Exactly what year model is the motor?

Re: 8-cyl outboard problems

Its a 275hp, I don't have the exact year but it is between 85-88. Can I order a rebuild kit with the 8 needle and seat with it? If so where is the best place to get them? I have to run this by the dept. before I can order but hopefully they will let me.

Thanks for your input.

Also, what is the diffenerence int he NGK and the champion spark plugs? We just put new ngk's in it.

Re: 8-cyl outboard problems

The NGK's are probably hotter. I'd get them out and put the champions back in before we have piston issues. If it were mine I'd usle the QL77JC4's. You can use the NGKs but I'd richen up the high speed and the mid range jets.

You'll probably get the carb kits from a dealer. Any Evinrude or Johnson dealer will probably have them in stock.

Being a 275 it's probably a small bore which was made from 1985 to 87. The target rpm on that one will be 6000-6200 with an average load.

The fuel delivery system is critical. Make sure everything is absolutely right.

Re: 8-cyl outboard problems

Well we called Johnson and gave them what we thought is the model number (BE2751XC). They said they believe it is an '85 model. Instead of going back through the records that our treasurer has, is there anyway that I can open the carb up to see if we need new needles and seats? Also the RPM gauge isn't working so I am going to have to look into that too. If i can get in there and just clean the carb out for the time being to see if that will help I would like to do that. We don't have another meeting til Sept. 8th to vote and see if we can get everything for it.

Re: 8-cyl outboard problems

It's probably 275TXCO which is a 1985 25" 275.

Usually a dead give away on carbs is the plug in the bottom of the carb bowl. Pull it and see if the end of it in the bowl is clean or dirty. The way you describe the way it runs I'd suspect carb issues.

Remember, the carb not only feeds the motor fuel but oil (lifeblood) too. Not enough fuel = not enough oil. Oil keeps pistons happy.

Re: 8-cyl outboard problems

If it's an 85 to 87 it'll have 2 power packs, one on each side behind the flywheel. Here's another tip - the V8s are not wired like a V6 where the pack on the port side is connected to the port coils and the starboard pack runs the starboard coils. In otherwords V6 packs are wired side to side.

The V8 packs are wired top 4 and bottom 4. One pack will run the top 4 cylinders, the other pack runs the bottom 4. You'd be surprised how many times someone looks at the wiring and thinks it's wrong because it's wired top 4 & bottom 4. That usually gets straigtened out when the new pistons are put in.

Re: 8-cyl outboard problems

Ok, thanks for the pointers. When I get home from work tonight I'll head to the firhouse and check out the carb situation. Also, the boat has an oil tank in the back to mix fuel and oil but the mechanic that rebuilt it unhooked it and said it would be better to mix ourselves in the tank so we know it is right. Do you believe this statement? Another member and myself had talked about trying to hook it back up.


Just kinda for reference....do you know about how fast the boat should run? Is 43 about where it should be? I have a 19.5ft with I/O 305 and it runs 46-47 with 8 people. It seems like the fireboat should be faster than 41-43 with 2 people in it.

Re: 8-cyl outboard problems

Personally I wouldn't have an outboard without oil injection. just make sure it has the newer style 4 wire pumps. For the moment there's nothing wrong with running pre-mix.

The speed all depends on what rpm it's getting and the set up. First we have to make sure it's running right.

Update: 8-cyl outboard problems

Update: 8-cyl outboard problems

Well, yesterday after work, we checked the plugs and they were clean. I didn't know this, but last week they took all of them plugs out to make sure all the carbs were getting gas and everything seemed to check out fine. I talked to a couple of the guys who were dealing with the boat work in the beginning (about a 1 to 1 1/2 years ago). They said that it wasn't rebuilt, it is a brand new long block on it, so there shouldn't be any problems with that. Also, last night we took the gas can out of our small boat and hooked it up instead of using the gas in the tank to see if it would run any better. We aren't 100% sure that its not getting air somehow in the lines. Well it did the same spittin, sputterin, and coughin as usual. After it started to run and idle fine, 2 guys took it to the river and it ran worse than it ever has. We may end up taking it to the Johnson dealership to have them diagnose the problem because we don't have anyone who has ever worked much on outboards especially this large. The treasurer also said that we have over 12,000 in everything we've done to it and the boat running would probably on be worth a few grand. Thanks for your help and if you can think of anything else to test and see what it is, I am open for anything. Oh yeah, I traced the wires to the power packs and they are wire up to 4 on top and 4 on bottom.

Re: Update: 8-cyl outboard problems

Re: Update: 8-cyl outboard problems

Clean the carbs.

There is no such thing as a "long block" in the outboard world. It probably has a new powerhead (which does not include new carbs or ignition) and even if the carbs were cleaned 1 1/2 years ago they're probably due again.