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Author Topic:   New Mercury Break-In
cjmarlin posted 10-28-2002 03:56 PM ET (US)   Profile for cjmarlin   Send Email to cjmarlin  
I have the 90-HP 2-stroke Mercury on the new 170-Montauk. When I first got it, the engine seemed to smoke quite a bit. The dealer told me this is not unusual, that it had special break-in oil and that it would stop when fully broken in. I have broken the engine in following the owner's manual and have refilled the oil tanks at least four or five times. When I have not started in a week or so, it still seems to smoke too much. Another issue is that I have not been able to get the engine (according to the tach) to ever run above 5000 RPM. The engine came with the standard Mercury prop. I am taking the boat to the dealer for winter storage and will ask about the engine smoke and inability to get more RPM. Before I do, I would appreciate any input anyone has on these subjects so I am armed with some data before I talk with him.
thebone12 posted 10-28-2002 04:08 PM ET (US)     Profile for thebone12  Send Email to thebone12     
It's a two stroke, sounds normal with the smoke, and the RPM could also be normal depending on the prop!
baybug posted 10-28-2002 04:14 PM ET (US)     Profile for baybug  Send Email to baybug     
Smoke sounds like a Merc. As for the RPMs, your prop is pitched too high. I would assume that you don't have as much of a hole shot as you would expect. Drop 2-inches in pitch which in theory will increase your RPM.
newt posted 10-28-2002 04:18 PM ET (US)     Profile for newt  Send Email to newt     
What prop are you using? I have a 21-inch Merc aluminum prop and my Merc 90 2s swings it more than 5500 RPM.

Special break in oil? Mine came with standard Merc oil, but I used pre-mix gas in addition to the oil injection, and it did smoke quite a bit during break in. Are you running straight gas in the tanks now?

The smoke on startup is normal, but you should be getting more rpms.

Again,what prop do you have?

cjmarlin posted 10-28-2002 05:22 PM ET (US)     Profile for cjmarlin  Send Email to cjmarlin     
My prop size is 12 3/4 by 21". You are right about the break-in oil. It was mixed with the gas during the first few tanks, not a special oil in the oil reservior. I have run straight gas at least 5 tanks since then. When WOT on clear water when I get near 5000 RPM it seems like the prop is slipping or something holding back. But it won't go past 5000. Also, just want to say how much - as a new powerboater - I have been helped by everyone. I should have read everything on this site before I ever bought my boat - it would have been a great help - in rigging it right away. I am an experienced boater (sailor)who looked at many boats before I changed to a Whaler.
thebone12 posted 10-28-2002 05:38 PM ET (US)     Profile for thebone12  Send Email to thebone12     
You may also have the motor trimmed down too far.
Tom W Clark posted 10-28-2002 05:46 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

If you are new to small powerboats I am wondering if you are familiar with the benefits of the power trim your motor has.

Generally, trimming the motor out will lift the bow of the hull and allow more air to slip under the hull and help lift it and reduce the amount of water in contact with the hull. This will reduce resistance and allow the boat to go faster and the motor to increase rpm's.

The difference between having the motor trimmed all the way in and all the way out can result in a difference of several hundred rpm's.

Were you able to measure your boat speed with a GPS when you were running at wide open throttle? If so how fast was your boat going? How much weight was on board when you were operating the boat at full power?

Tom W Clark posted 10-28-2002 05:57 PM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     

I'm sorry. I just reread you post more thoroughly. You have the new MT 170? If newt is getting 5500 rpm with the same motor and propeller on his Classic Montauk then I think you are doing very well to be getting 5000 rpm on the new MT 170.

newt's boat weighs maybe 950 pounds vs. 1440 pounds for you boat. I suspect you have too tall a pitch prop. Try a 19" pitch or maybe even a 17" pitch prop.

Clark Roberts posted 10-28-2002 06:01 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
cj, your engine's auto oiling pump has two postions (designated with scribe marks-see maint manual or your dealer) and after break-in you should move or have moved, the pump lever position to the lowest oiling rate position... Happy Whalin'.. Clark.. SCN
Barry posted 10-28-2002 06:06 PM ET (US)     Profile for Barry  Send Email to Barry     
You might check the throttle linkage to make sure you are really getting 100% when the throttle is all the way forward.
jimh posted 10-29-2002 09:33 AM ET (US)     Profile for jimh  Send Email to jimh     
[Changed topic--was "Performance Problems"--jimh]
jimh posted 10-29-2002 09:39 AM ET (US)     Profile for jimh  Send Email to jimh     
According to Whaler's test data (see , a 170-Montauk with the 90-HP 2-stroke can hit 43.7 MPH.

I'd read the owner's manual cover to cover and see what they say about break in procedures, throttle linkage, oil injection calibration, etc. And I'd get the dealer involved before I started changing anything on a new engine.

Matthew posted 10-29-2002 12:44 PM ET (US)     Profile for Matthew  Send Email to Matthew     
I have the same boat, outboard and prop, and turn the same rpms as you (maybe just a nudge over 5000) I think we both are very close to max performance with our present set up.

I wasn't aware of the 2 positions on the auto-oiling pump and should adjust this--Thanks Clark!


newt posted 10-29-2002 12:53 PM ET (US)     Profile for newt  Send Email to newt     
Clark, could you elaborate on the oil pump setting? Do you know if the '03 mercs have it, because my owners manual doesn't even mention it!

Maybe I should buy the service manual.

Clark Roberts posted 10-29-2002 02:46 PM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Newt, get or look at a service manual and it is a simple proceedure... Note: I haven't looked at a 2003 so can't be sure they haven't changed to a single setting... but I've had a dozen at least of these 3cyl 70-90hp Mercs to 2000 year model and all have the two settings. If you look at the oil actuating rod (from the throttle linkage) you will see that it simply rotates a small disc attached to the oil pump outlet. This disc (or disk if you prefer) will have two (or three) scribe marks on it and the stationary pump body has an index mark for alignment... Normal oil flow is obtained with left most scribe mark aligned with the index. It's much more simple than it sounds, really! I just have trouble explaining it. I'm looking at a picture of it right now on page 38-2 of Merc service manual for 87 through 93 70-100hp 3 & 4 cyl Mercs/Mariners. A service manual is a good ivestment no matter what engine you have and dealer has them for around 20-40 bucks... etc...etc...etc.. Happy Whalin'... Clark.. Spruce Creek Navy
Wild Turkey posted 10-29-2002 02:56 PM ET (US)     Profile for Wild Turkey  Send Email to Wild Turkey     

I agree with Tom W. Clark - too tall prop pitch.

I have no clue why dealers are providing this prop with the new Montauk 170/Mercury 90HP 2-stroke setup.

It seems that people (on this forum) know more about Boston Whalers than the dealers.

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