100hp merc outboards

[MAXX40X]

Greetings
I have a question that is probably going to open a can of worms. Never the less, hang on;
Here we go. In the opinion (yeah I know) In the opinion of the most seasoned boaters on this forum running Merc outboards, and or experienced marine mechanics? what would be the best all-around 100hp Merc, between the years1974 to 1976 with tilt/trim. This motor will be pushing an aluminum hull 18? Starcraft SS. Primarily, the boat will be used for fishing, and occasionally pulling a tube. I guess its not that hard of a question; but since I don?t know that much about outboards, it?s a real hair-puller for me.
Thank you for your time.

 

[Barnacle_Bill]

Re: 100hp merc outboards

The one that was taken care of the best.

 

[Faztbullet]

Re: 100hp merc outboards

First of all I would look for something in the 1980 year and above as it has a better ignition system ... and as bhile posted

 

[MAXX40X]

Re: 100hp merc outboards

The one that was taken care of the best.

What I have now is a 1992 100hp Merc 2+2 tilt/trim. Built a stand, Pulled the motor, and started reading /asking questions about this motor. Seams the consensus is a love-it/hate-it, relationship. In any event, I ran a compression check yesterday with my trusty Snap off, er Snap On compression gauge; #s are as follows 135-135-134-135. I ran the check twice, with my gauge; And then ran it a third time with my buddy?s gauge. Same numbers. That told me a lot. (1) the guy I bought the boat from said the motor was a good one; true story; (2) there are still honest men among us.
It seams that everyone wants to pull the oil injection unit, and run pre mix. I understand lean condition/smoked motor. ( I have built a few motors in my day; 2 stroke and 4 stroke ; NOT BOAT MOTORS). And here again, there are thousands of opinions. I guess I am looking for the peace of mind of never hearing this motor grind to a halt 4 miles from any safe harbor.
It is also believed that this motor has a soft lower unit. ie: don?t tune it; the lower unit wont take the added stress.
I only want to do what is best for the motor. I don?t wanna be working on it every time I get it on the water.
Thanks for any and all response.

 

[sschefer]

Keep that 92' !!!

Keep that 92' !!!

The motor you have is a good motor. Yes the L/U's are small but they will still take a lot of abuse. Replacing a L/U is easy and they are relatively inexpensive compared to a maintaining an older inline.

The oil systems on the motors of this era are very reliable. Your's is specially nice since the tank sits on the engine and is not adding extra hoses and a pressure system to make it work. Replacing the oil pump is a 20 minute job and it's rare for the crankshaft gear to fail.

Here's something to put in your back pocket. A little outside the box if you will. If you premix your fuel and then for some reason you need to drain your tank, you can't filter it and burn it in your car. You're pretty much stuck with a bunch of lawnmower gas.. Stop by and I'll give you 20 gals if you want it.

The most common problem with these engines is with the mechanical injectors on cylinders 3 & 4. Most folks don't know they are there and that there is a filter sitting behind the oil tank. A half hour maintenance and a dose of Quicksilver Quickclean or a annual pre-season Sea Foam tuneup will keep the injectors clean. Change the filter pre-season when you change the fuel filter.

Annual pre-season prep for your motor should be about 4 hours labor and under 200.00 in parts.

It's pretty hard to beat that and compared to the cost of buying an older motor with a lot of "No Longer Available", (NLA) parts. I think you would be making a huge mistake if you went to an older motor.

 

[MAXX40X]

Re: Keep that 92' !!!

Re: Keep that 92' !!!

The motor you have is a good motor. Yes the L/U's are small but they will still take a lot of abuse. Replacing a L/U is easy and they are relatively inexpensive compared to a maintaining an older inline.

The oil systems on the motors of this era are very reliable. Your's is specially nice since the tank sits on the engine and is not adding extra hoses and a pressure system to make it work. Replacing the oil pump is a 20 minute job and it's rare for the crankshaft gear to fail.

Here's something to put in your back pocket. A little outside the box if you will. If you premix your fuel and then for some reason you need to drain your tank, you can't filter it and burn it in your car. You're pretty much stuck with a bunch of lawnmower gas.. Stop by and I'll give you 20 gals if you want it.

The most common problem with these engines is with the mechanical injectors on cylinders 3 & 4. Most folks don't know they are there and that there is a filter sitting behind the oil tank. A half hour maintenance and a dose of Quicksilver Quickclean or a annual pre-season Sea Foam tuneup will keep the injectors clean. Change the filter pre-season when you change the fuel filter.

Annual pre-season prep for your motor should be about 4 hours labor and under 200.00 in parts.

It's pretty hard to beat that and compared to the cost of buying an older motor with a lot of "No Longer Available", (NLA) parts. I think you would be making a huge mistake if you went to an older motor.

Ok; I am going to keep the motor; I was thinking it would be cool to have the same year motor / boat ,1976. and I was thinking of a (100hp Tower of Power) and if I can find one of that year, that needs work;(obviously) I will put it aside for this long Ohio winter and rebuild it. I have just heard and read so many horror stories in regard to the 2+2 motors. I also know most of those story?s are due to neglect/abuse/ inexperienced shade tree mechanics etc?
Then again, if something does come up with the 2+2 , I know you boys on this forum will be there; shirt sleeves rolled up and ready to help/assist/and answer all questions stupid or not. The only other question I will hinder you with at this time is this. What prop (money not being the limiting factor) should I run with my combination? 18? Starcraft SS/ 1992 100hp 2+2 = fishing/putting along/ occasionally pulling a tube.
Thank you again for the response.
You guys are awesome

 

[sschefer]

Re: 100hp merc outboards

Run a 17p 3 blade or a 16p 4 blade. I've run nearly the same configuration as you. Top speed will be about 35 mph and RPM's wll be right.

 

[Dave1027]

Re: Keep that 92' !!!

Re: Keep that 92' !!!

The only other question I will hinder you with at this time is this. What prop (money not being the limiting factor) should I run with my combination? 18? Starcraft SS/ 1992 100hp 2+2 = fishing/putting along/ occasionally pulling a tube.

To answer that we'd need to know your current prop size and WOT RPM.

 

[sschefer]

Re: Keep that 92' !!!

Re: Keep that 92' !!!

To answer that we'd need to know your current prop size and WOT RPM.

I agree but since I have the same boat and had the same motor I felt pretty well qualified to answer. Max RPM is 5800 but HP starts to fall off at around 5200. The hull design is also restrictive with it's deep V and long keel. Smooth riding but not very fast. 35 is about tops with that motor so don't go spending a hunk of money on props for 1 or 2 mph, it just isn't worth it.

 

[Dave1027]

Re: 100hp merc outboards

I was typing my reply when you posted. If you had the same setup then you ought to know.

 

[79Merc80]

Re: 100hp merc outboards

I'm a little confused. Everything I have seen says that the 100hp was made in 1963, 64, 65, 68, and 69 as an inline 6 and then again starting in 88 as the inline 4 2+2. The only option would be is a 90 or a 115. Also, the 88 and up 100hp is close to the same propshaft power as the older 115.

Just some food for thought

 

[sschefer]

Re: 100hp merc outboards

I was typing my reply when you posted. If you had the same setup then you ought to know.

LOL... Stuff happens... This is one of the very few areas that I am well versed.

 

[MAXX40X]

Re: 100hp merc outboards

LOL... Stuff happens... This is one of the very few areas that I am well versed.

Well versed is exactly what I need at this point. I have never had the boat and current motor in the water. My objective is to have a dependable fishing/pleasure craft; that said, the hull has been completely stripped/ media blasted and ready for further modification. I have vary little money in boat/motor/traler; (I did hear the motor run;sounded good)and knew total/proper restoration on both boat and motor was/is labor intensive. Money isn?t an issue. I will do this once, and do it right. I am retired, and needed another project now that i have sold my motorcycle shop; and have always loved boats; and I really like the lines of this 18?Starcraft SS. Speed isn?t what I wanted. Had that been the case I would have bought a big block I/O; that isn?t what I wanted.
In any event, thank all of you for the response; ohhh yeah. There will be more questions.
Thank you again.