Re: 90h.p. mercury 3 cyln.
Rocky,<br />I must be one of the apparently extremely rare happy owners of a 90hp 3cyl Merc. I have the utmost respect for JB's opinions and his wide knowledge of outboards but I disagree with his opinion on this motor, JB's comments are based on his personal experiences and so are mine. This motor has been in production since 1987 which is rather a long time for a "lousy" motor to be on the market, if you read some of the past posts on this board and other boards you will find some very positive opinions, both from experienced techs and owners, some with upwards of a 1000hrs operation. <br /><br />I have been around boats for nearly 50 yrs and owned my own boats for 30 yrs powered both by OMC and Merc motors, IMHO my 2000 90hp Merc is the best outboard I have owned. That does not deny the fact that the motor seems to need a bit of fine tuning to get the best operation, this seems to be because of incorrect setup and adjustments during installation. As djohns19 suggested read the past posts and and you will find a lot of good advice to eliminate most of your problems.<br /><br />When new, my motor had some of the problems you are experiencing, it would stall at idle and sometimes be sluggish starting, I borrowed a manual and went through the link & sync procedure, with the following observations of my own and advice from posts on this board.<br /># carb idle mixture screw settings are absolutely critical that they are set with boat in the water, if done in a test tank, the settings will be lean in the water (hard starting - poor idle)<br /># correct clearance between roller on carb linkage and cam on throttle arm is essential (on 2000 model this is .005 to .020) this varies between models with some older versions clearance being double the above settings ( I have seen motors supposedly correctly setup to go, with clearances of 1/8") There is only a primary pickup on the throttle so the motor goes straight from idle to main jets this can be responsible for the bogging during acceleration.<br /># the motors run extremely cool and sometimes need a thermostat change to a higher operating temperature to operate smoothly in colder climates (something I have no experience with! Because of where I live).<br /># the motors seem to need about 40 to 50 hrs running before they are run in and will require adjustments to idle speed and mixture settings during this period for good results, once they are run in, the settings don't generally require further tweaking. Carb mixture screws are very sensitive, 1/8 of a turn richer or leaner can make a major difference to idle.<br /><br />After doing these checks and adjustments, I now have a motor that starts first turn of the key (hot or cold), a smooth idle and very good acceleration to planing speed, the only brief hesitation is during the first acceleration of the day to planing speed which follows a 1/2 mile of no wake at 1200 rpm through a resticted area from the ramp on a cold motor, the motor will accelerate cleanly and very rapidly from idle to WOT (5300 - 5400 rpm) for rest of the day. The motor will be 3 yrs old in August and just continues to run better all the time and consistently returns fuel consumption figures of around 6 to 7 miles per gallon on a 17' half cabin f/glass boat with a total loaded weight of 2,600lb.<br />Sorry about the long winded post but I feel a lot of the critisism of the motor is due to poor / incorrect setup, there are a lot of 75 & 90 3cyl Mercs in my area but you never see any traded on other motors or for sale without a boat, and the owners I speak to are quite satisfied after they have done some fine tuning.<br />regards Bob
<br /><br />Moving this to Outboard Engine Forum.