Power pack on Johnson 175

[gradyrod]

engine has a high speed very brief loss of power (cuts out momentarily then comes right back in about 1 second) that I cannot get rid of. I replaced the optical sensor but that didn't help (1998 175hp Johnson Ocean Runner carb). I guess the only thing left is the power pack replacement. Anyone familiar with how this job goes? Is it a simple bolt on replacement, or do I need to time the engine after replacing the power pack?

Thanks for any advice!

Rod
1985 Fisherman 204

 

[BobP]

Hi tension coils good?

I did the power pack plug and play job, don't recall having to do any timing checks. I had a 150, there were two power packs I recall, one for each bank, My 200 Johnson had one power pack for both heads, located in the middle up there. Did that one more than once.

You may have a loose/corroded ground, that's what I found with the power pack after blowng $125 onm a new one, the wire in the jacket corroded internally (OMC used bare copper - cheap bastards).

I remember tapping around with a big scredriver handle and when I hit the the powr pack the RPM perked up for a while. U may want to tap around and see what happens.

I say you have a bad ground or otherwise bad connection/wire somewhere, I had to strip the entire harness and check each wire, ran new ground wires. also had corrosion in T&T control box causing intermittant operation.

 

[sfc2113]

Not that this is your issue but thought.
I might add something to look at here, Friend had the same problem on 1997 150 He had the power pack replaced and did not fix. It still happened at high rpm

He took it to 3 other marinas in Wildwood, NJ, they told him he prob may have had a bad pack installed. Replaced it again after fighting with the marina that installed it. No luck. Last Marina he took it to somewhere in cape may, the mech took it for a ride, told him it was his prop cavitating bent blade and out of bal? replaced it and been running for 2 yrs no prob.

 

[BobP]

Good point-

Did the motor missfire or just speed up a bit (to the ear) on RPM ?

If the motor doesn't have a rev limiter cutout, motor shouldn't miss a beat for a prop spin. But instead act more like getting sea weed wrapped on a prop.

 

[gradyrod]

engine missing

first of all thanks everyone for some great ideas! i am especially wary of replacing the pwer pack now that i read about the guy who replaced it twice and it didn't help him!

as for the exact problem: I motor along at about 3200 to 3500 rpm and all is smooth. good strong acceleration, holds speed nicely, then once in a while the engine will just cut out for a fraction of a second then come right back to smooth running at the same 3200 or so rpm.

regarding the cavitation, can anyone tell me how badly a prop has to be dinged in order for this slippage to take place? remember, my engine drops revs, not increase revs before returning to normal running.

thanks again!

Rod

 

[sfc2113]

I did not get to see his prop, but the stuff he drives his boats thru , I would not be suprised that is was pretty dinged up. He said was not looking healthy. And one of the blades was slightly bent. Not noticeable untile they put it on a spinner or balancer or whatever it's called. I was on the boat when it was happening and rmps went up before it started missing.When he backed off on the throttle like around 3-4k rmp it ran fine. Boat still moved at around 30knots at that rpm, but he was not happy with that.
The cavation thing may be a shot in the dark to try first, get your prop checked and balanced. He gave over 600$ in troubleshooting labor and parts to the marina that replaced the power pack. They did not charge him for the second one.

Like BobP said also, a bad ground can cause all kinds of weird trouble.

I would clean up all the ground wires and make sure they have good continuity to the engine block and Batt Neg
And if you have dual batt switch, Take a look at that too.