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engine doesn't go pass 3000 rpm under load

Did this happen recently and suddenly or was there a gradual loss of rpm/power over time?

More info from you might help someone here assist you in figuring out what's happening. Things like:

Have you had the outboard long or is it a recent purchase?

List any work done prior to the problem occuring.

List anything you've done trying to correct this issue.

Have you experienced the engine misfiring at all?

When was the last time the spark plugs were checked/gapped/replaced?

Do you run a water separator for the fuel system? If so when did you last drain/service it?

How old is the fuel filter? Your best guess will do. They are $12 and still available from www.boats.net

Does the fuel primer bulb stay hard?

It usually requires a helper but have you tried squeezing the primer bulb while trying to accelerate under load?

Do you regularly drain your carburetors and check for contaminates/water?

Have you ever had overheating issues or poor waterpump flow (weak pisser stream)?

Do you have the service manual?

Please add anything else that comes to mind. Sometimes it's the little things that can help you find a solution and my list is by no means comprehensive.
 
Thanks for the response. William01: Always have fresh fuel.
jgmo: I had this motors from 1997. Had no problems other then regular maintenance issues. Once ethanol came into play that is when problems started. So had to run ethanol until they came out with non-ethanol fuel. But while running ethanol fuel i would run seafoam. I have overhauled the carbs twice and even replaced 2 which ran ok. But recently while out on the water as i was throttling up one engine would only go up to 3000 rpm and when i would return the throttle it would die out. But what is funny is that the engine runs fine under 3000 rpm. I replaced the fuel filter, spark plugs and even swapped out the #3/4 fuel pump with the same results. I'm about to re overhaul carbs again and start over. Compression and spark is good. Engine not burning oil which is a good thing. Or could it be the air/fuel mixture is off on carb 3/4? I do run a fuel/water separator and fuel in tank is water free. I have no overheating issues, the pisser is weak while flushing, but pretty strong in the water. In Hawaii we do have problems with salt build up and scaling. I replace the thermostat and waterpump yearly. Plugs are replaced yearly. I do have a service manual. The only thing that i haven't check is the timing but it idles smooth. I want to run this engine to the ground before replacing LOL. FYI, I run twin BF90's and it's only starboard engine that is driving me NUTZ! LOL Also I haven't checked the fuel pump pressure or if there is a way.
 
Dang! See, I knew someone would have a better list of things....I just didn't know it would be you!

It sounds like you've really taken good care of those outboards and you know WAY more about them than I ever will.
They're 2 years older than my Dodge Gen 1 Durango and it's OLD!

I think you're probably on the right track for this looking into the carbs. As you probably already know, the balance for them is pretty important for full power and smooth operation. You didn't mention balancing them but I'm guessing that you do.

The running ok up to 3k and then falling out and dying during decel thing sure makes me think fuel delivery but I suppose it could be something else. Do you know what sort of engine protection is built into the CDI?

The nice thing about having a good runner right next to it is that you can swap things you are suspicious of like ignition coils or the CDI.

But I don't think I would change the plan to address the carbs first. Especially since you're probably getting pretty good at cleaning them.

Please let us know how it goes for you.
 
Hahaha the funny thing about this whole story is that when i bought the boat (2nd owner) I stripped the motor down to the block. As former mechanic i wanted to see what these motors were all about. BUT, I haven't seriously turned wrench for many many many years. LOL
As far as balancing the carbs, I never did that or told to do that. Not even when I worked on cars. So it's good to know. I have a strong assumption that you are correct and it all has to do with fuel pressure. Either clogged jet, port or some S#$t. Too bad boats.net doesn't carry new carbs. But I got my hands on 2 other engines (same size and year) which i can refurbish parts that are dis continued. I will keep ya posted. Aloha
 
jgmo said:
Dang! See, I knew someone would have a better list of things....I just didn't know it would be you!

It sounds like you've really taken good care of those outboards and you know WAY more about them than I ever will.
They're 2 years older than my Dodge Gen 1 Durango and it's OLD!

I think you're probably on the right track for this looking into the carbs. As you probably already know, the balance for them is pretty important for full power and smooth operation. You didn't mention balancing them but I'm guessing that you do.

The running ok up to 3k and then falling out and dying during decel thing sure makes me think fuel delivery but I suppose it could be something else. Do you know what sort of engine protection is built into the CDI?

The nice thing about having a good runner right next to it is that you can swap things you are suspicious of like ignition coils or the CDI.

But I don't think I would change the plan to address the carbs first. Especially since you're probably getting pretty good at cleaning them.

Please let us know how it goes for you.
Click to expand...
Ok update on engine problems. Honda 90 hp has 4 carbs. 1-4 top to bottom. While overhauling the carb, found that #1 carb float needle was closed shut. So no fuel going into carb #1. Also noticed all the float levels on both engines were off. After overhauling carbs and adjusting float levels I field tested the boat and tada, problem solved. I also checked compression and all cylinders were in specs. So it makes sense to overhaul and take your time. What is really surprising is that the engine is 1997 model and burn 1.5 gallons an hour both engines together. Its good to adjust air/fuel mixture by checking the spark plugs. Start with 2 1/2 turns and +/- 1/4 turns if running rich or lean.
 
Alright! Good news!
Thanks for the update and explanation of the steps you took.
Hope you have a great boating season.
 
Find the incased high speed fuel pump location,open it and clean/replace the filter and screen,look for and clean any ethanol scale.
See if that helps.
 
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