I am looking into buying twin 90 four stroke engines but I would need to troll with them I have heard that they are quiet, but as quiet as a 9.9 2 stroke a trolling speed?

How important is it to have counter rotating props? I have heard that it is harder to control the boat without counter rotating props

Thanks for the replys

You probably will end up trolling too fast, even on a single 90. The reason is that your props are probably optimized for top end, say, 19-21" pitch (guess). So, if you are idling at 800 RPM, with 2:1 lower-end gearing, and knocking off 50% for slip, your real-world minimum trolling speed is 4 MPH, probably faster than you want to be going.

A 9.9 kicker usually carries a 9" pitch prop, with more slip, for a minimum trolling speed of maybe 1 MPH.

Regards.

Mike

I have a 115HP Merc 4 stroke and a 9.9 Merc Bigfoot 4 stroke... I troll with the 115 in the Ocean all the time, and it works great.. but I think its too fast for the rivers.. just my .02

Just another question for anybody who cares. What is the niose level for a 90 or bigger 4 stroke at trolling speed compared to a small two stroke?

I troll with my Honda 90 on my 21' aluminum workboat exclusively and love it! I run a lower pitch prop and can easily putt along at 1.5 knots @ 550 rpm. Cannot hear the engine running and uses basically no fuel. I also rigged a secondary throttle cable with a fine-tune knob (instead of a lever) that allows me to tweak the rpm up or down in 10 rpm increments. I love not having to own or mess with a kicker motor.

What pitch prop?

Mike, it's a 13.75" dia x 15" pitch 3 blade aluminum heavy load prop (Propco # LM57-15SP) usually used on heavier workboats or house barges. I also have a neat 4 blade alum from them (QRJ-T LM58-17SP) for better cruising speed (30 knots @ 5000 rpm instead of 25) if I'm not going to be doing any trolling and not loading the boat too heavy (it's a heavy boat to begin with).

Thanks!

I'm trying to figure out how much slip various prop/RPM/boat combinations provide.

My 20' boat idles at 800 RPM, 19" pitch prop, 2:1 ratio, and I get about 3+ MPH with the trim all the way down. That's about 50% slip.

Regards.

Mike
Woodinville