1992 C115TLRQ Miss

[LJ Bassmaster]

I am attempting to diagnose a problem that I have been having off and on that has been occurring on a more frequent note. I am having an extreme miss when driving down the lake, above 3500rpms to WOT. It occurs very randomly and goes away if I come off plane to an idle. Then I can occur as normal until it does it again. The boat runs as strong as it does when I bought it. I know its either fuel or spark, but haven't had much time to really put into it. Thanks! -LJ

[99yam40]

you need to be testing when the problem occurs to see what is happening.
all we can do is guess if it is spark or fuel related.

That said most motors end up fuel related
have you checked fuel pump

[LJ Bassmaster]

Tested the CDI and coils according to the clymers manual, all within spec. Haven't checked the fuel pump as of yet.

[TownsendsFJR1300]

Back to basic's, when were NEW spark plugs installed?

I had a similar issue on my 4 stroke (hestitation and the RPM dropping at 5300 down to 4800 or so). New plugs ONLY, fixed it, back to 5900 WOT..

Your symptoms sound like plugs... Easier to fire at idle, harder at higher RPM's, ESPECIALLY if WORN and the gaps OPEN UP from wear (misfire big time)..



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[LJ Bassmaster]

I replace plugs every few months for good measure. They have been in for about a month, I have replaced them since the issue began. I have replaced the fuel pump and it cured the cold start issue on the muffs, I have not had a chance to lake test the boat yet.

[LJ Bassmaster]

The same problem occured again, however this time the alarm in the control box went off, not long after that, I noticed an extremely weak water stream out the engine, does the motor kill power if it is overheating? New waterpump going in soon...

[TownsendsFJR1300]

Some engines drop RPM's when they over heat. IDK if yours does-probably...

How old is the water pump?

And get the entire kit, NOT just the impeller...

[LJ Bassmaster]

Waterpump was replaced when the lower unit was replaced in January with an SEI replacement

[TownsendsFJR1300]

I'm assuming your in fresh water operating in a lake so salt build up in the head isn't likely.

With the pisser slowing, the alarm going off, the WP is the first thing I'd be checking. IMO, get a genuine OEM kit.

Is there much / any silt/ sand in the lake that could get sucked in the engine?


Also, is the engine carbed or FIed?



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[99yam40]

Does this rig not have gauges that shows what is happening?
being a C115
only alarm would be overheat.

weak stream should point you to water pump or PRV maybe
check stats or replace them also