170 rebuild first start - wet! (Update: now dry)

[Collector Inspector]

A quick video showing the red high-temp RTV sealing the outside of the head. This motor starts, idles, runs very well in the bin. In and out of gear without having to rev it up a bit like the other FNR gearbox motors I have. Very smooth running overall.

Next up, sea trials...

It runs.

Does not leak water.

Use it as is.

Even if a dribble on the outside not an issue as you have indicated that the cylinder fire seal is functional.

It is old...put it on a transom and do some laps of whatever aye?

You stress too much and we do not judge anyway.

B

[andrew]

Thanks Charles, good to know the cylinder might be salvageable over the longer term, with a small haricut.

Bruce, yes a fun project for sure, look forward to putting around with a mythical 170 model.

Now onto my next 170 question topic: spark plugs. The 170 takes 14mm diameter plugs with 19mm reach, medium heat range.

The owner's manual states Champion N3 or N4 plug should be used, which I don't have access to (current versions from Champion appear to be N3C and N4C). Suitable alternatives suggested on a couple spark plug websites are NGK B8ES and B7ES, respectively, the 8 being slightly cooler than the 7.

Any suggestions on whether to look for cooler (8) or hotter (7) plug for the 170 in general, and for a patched up cylinder like mine in particular? Thinking cooler may be the way to go at first.

Also, the 170 manual inconsistently states both 0.035” (9mm) and 0.025” (6mm) gaps to be used. Is one of these more correct and/or should I be somewhere in the middle?

[Charles uk]

If you read the manual carefully it will probably say if you have the mk 3 wipac CDI (White one) 35 thou & the mk4 CDI 25 thou.

Those gaps are 0.9mm & 0.6mm.

[andrew]

Under the Spark Plug section it specifies 0.035" and under the laying up section it specifies 0.025". Very confusing. No mention of difference depending ignition.

My outstanding questions for input please:
1) Correct gap for this motor. It's got a MK4 so 25 thou?
2) Better to use a cooler or hotter plug (though not much difference expected between the NGK 7 and 8 heat range)
3) Resistor spark plugs, prefer to avoid them but hard to find non-resistor types. Assume OK with CD ignition absent other options? Ran fine in test tank but not yet tried under normal operating conditions.

thanks again!