Re: 1986 merc 170
you are talking about a mercruiser 470 170 hp. 4 cylinder, internal water cooling. i know it well. i have 2 boats - one with this motor and one with a 4.3 205 hp.
some people love them , some hate them, i feel indifferent so ill just run through a few comparisons with the 4.3 v6 the engine that basically replaced it.
start with power... usable power
the 170 hp 470 is alot more "torquey" the the 4.3. its not even close actually. in similar boats the 470/170 will usually go faster because the weight is the factor. the 470 is aluminum so its much lighter. to be honest in overall performance i would give the edge to the 470, but it may be dependant on what boat you are putting it in
reliability is a toss up - the 470 has some design flaws right out of the box - the charging system being one of them. the old style stator and voltage regulator is prone to failure and pricy to fix. a simple 300 dollar alternator kit will remedy the situation tho. the other problem is over heating on the 470. it runs cool because of the freshwater cooling and heat exchanger, but should it get hot there will be big trouble because the block is aluminum and head is iron. other than that the 470 is fairly solid. its a quite peppy light engine that has a sweet system making it pretty much saltwater ready.
its main drawbacks.. its no longer produced, so prices for parts can get a little bit out of hand if the demand is full effect. you pretty much have to use ebay to get your parts and you never know what condition they are going to be in and what they will cost you. that is honestly the biggest advantage of the 4.3 over the 470.
the 4.3 is quite a serviceable engine in its own right.. parts are cheap and easy to get for all variations, all shops can work on them. but they are not without their problems either. they have a gauntlet of ignition issues and are more finicky than the 470. when i got rid of my 470 in favor of a remanned 4.3lx i thought i would gain reliability but that is not the case. i like the 470, but i dont love it. if its a choice for me to make again i would go with a 350 everytime. price is an issue, but not much of one really. you will spend it anyway
If you have to ask that question it is best to stay away from one. On the other hand if you are very mechanically inclined and not afraid to do major work, like replacing head gaskets, and cam seals depending on the condition of the engine and the boat, and a significant $discount$ (vs say a 4.3) it might be OK. Buyer beware!
