'94 70hp cuts on wot and rough sea

[papadakn]

Seems a bit strange but although the engine idles ok and runs stable on mid range rpm, when riding waves or turning hard it cuts only to pick up 3-4 seconds later.

I have: replaced fuel line and bulb, cleaned the fuel filters, opened and cleaned the carbs and replaced the fuel pump with no luck. Any ideas?

[99yam40]

you need to find out if it is loosing spark when that happens or if it is fuel related

[papadakn]

How can i test it? In the sea it's not possible to open the cowling, when on land the engine does not misbehave. It idles fine and revs up nicely. Under load it starts misbehaving

[99yam40]

might run a cable from motor to where you can monitor the input and output voltages of CDI to see if they are going away when problem shows up.

Also might move harness around where it goes to motor while running to see if that will cause motor to mess up

[mackwrench]

Does it matter what fuel level is it? I'd look at fuel tank pick up....The symptoms you describe are fuel related....the ingition system does'nt know if the boat is taking rough seas or turning.....If tank pick up pulls some air, it'll take 3/4 seconds to "re-prime" itself....Get a small portable tank and run it, see if theres a difference

[99yam40]

lines,pump, and carbs will not run out of fuel that fast

[axolotl98]

I would bet its electrical, something is not grounding properly and with the choppy sea, it loses momentarily contact.

[papadakn]

Does it matter what fuel level is it? I'd look at fuel tank pick up....The symptoms you describe are fuel related....the ingition system does'nt know if the boat is taking rough seas or turning.....If tank pick up pulls some air, it'll take 3/4 seconds to "re-prime" itself....Get a small portable tank and run it, see if theres a difference

No, fuel level does not affect the issue. I was thinking that maybe the carb bowls do not fill up with fuel and the cylinders are left without fuel but again, it doesn't make much sense. Today i also changed the spark plugs without noticeable improvement.

Is it the cdi that regulates the spark on the spark plugs?

[99yam40]

charge coils produce the voltage, CDI stores it, and pulsar coils tell CDI when to send it on to the plug coils you need to test to see what you have and what you do not

Key switch and kill switch ground the voltage so the spark is not making it to plugs when they are turned to off. if the wire in harness goes to ground at switches or in the harness there is no spark to plugs

[axolotl98]

Any update on the issue?

[papadakn]

Unfortunately no. I used the boat during last weekend, with the known issues. I didn't have the chance to further check it or have it inspected by a marine engine spe******t.

I have a hunch that it is fuel related. When i find some time i will open the carbs and change the needles, floats and gaskets. If it is not solved, then it has to be electrical.

[99yam40]

It is a lot easier to test what you can and if nothing wrong is found, then work on the things you can not test

[Bilge Rat]

Check all the battery connections, both ends motor and battery.
Is the battery strapped down?
If you have a battery disconnect switch check those connections, are those leads secure so they don't flap around.

[papadakn]

No it's not strapped down, it's in the same place where it has been the last 35 years

How could it be the battery? I think that after the motor starts, it produces it's own electricity and works fine even if the battery is disconnected.

[papadakn]

How can i check that all 3 cylinders work correctly when idling? Removing plugs from cyl 1&3 didnt produce much bogging as when i removed cyl 2 plug...