Some Mercruiser 170 assistance please

[TMania]

I own a 1986 Marathon, had extensive work done to the engine by a mechanic, but unsure of a few things.
1) Im a boat illiterate, so please bear with me, Im used to a rowboat.
2) Whats WOT stand for ?
3) What is the optimal speed/rpm for a 170 mercruiser ? (prefer rpm please)
4) Last question, after being out on the water for a few hours, and turning down to idle speed, the engine stall, sometimes, befor she stalls, she sounds like she's misfiring, stalls, but starts back up again, usually this happens after she reaches operating temperature, besides carburator needing rebuild, what else could cause this problem ? Thanks

 

[IVAZ]

Re: Some Mercruiser 170 assistance please

2- Wide Open Throttle
3- Is this a 4 cylinder engine?
4- Could also be fuel filters.

 

[IVAZ]

Re: Some Mercruiser 170 assistance please

If it is a 4 cylinder you have the Merc 470. WOT rpm range is 4200-4600.

 

[TMania]

Re: Some Mercruiser 170 assistance please

Thanks Ivaz, yes it is a 4 cyl. I appreciate your response, I wasn't sure of the rpm range cause I never ran the boat over 1800 rpm's, so didn't wanna blow anything up. due to the age and unfamiliarization, of this boat, I purchased it last august, and did a complete tune up.

 

[life_aquatic]

Re: Some Mercruiser 170 assistance please

No expert here, but I have an 89 170, on a 22 ft walk around cuddy. By myself with pretty full fuel I think I was getting about 4200 rpm at WOT (I could be off a couple hundred rpm, but it was definitely over 4000). This had me going about 30mph according to GPS. I felt like a very comfortable cruising speed of about 25 mph with the rpm maybe between 3200-3500.
I just got the boat last fall and had a pretty decent tuneup - carb rebuild, dist. cap, spark plugs and wire. My only issue has been that sometimes it will stall when I'm going from forward to reverse in delicate docking maneuvers, in front of a crowd of people sitting on a restaurant patio.

 

[TMania]

Re: Some Mercruiser 170 assistance please

I think 1 of the reasons I kept the boat around 1800 rpm's was due to the oil pressure rising, not exactly sure what the pressure was last time I took it out, but, you figure seeing that pressure rising isn't a good thing, I believe that was the reason I kept it around 1800 rpm's.

 

[IVAZ]

Re: Some Mercruiser 170 assistance please

I think 1 of the reasons I kept the boat around 1800 rpm's was due to the oil pressure rising, not exactly sure what the pressure was last time I took it out, but, you figure seeing that pressure rising isn't a good thing, I believe that was the reason I kept it around 1800 rpm's.

Actually it is a good thing. RPMs increasing an oil psi dropping, that?s where the concern should be.