RARE Merc Short Shaft (16in) 150hp inline six

[CAPTAINRICH67]

HI...This is my first time posting on this site. I came across a Merc 150hp with a 16inch shaft. I am in California and nobody out here seems to know much about it. I came on an old glastron. Wrong motor for this boat. Needs to be on a small speed boat. So...I replaced the motor with a 140 evinrude 4. Does anyone know about these short shaft Mercs? It runs good..had the carbs rebuilt and good 119-120 compression.

[milkdud]

show a picture. Im gonna send you a pm. conrad

[milkdud]

worth depends on several things. Most 150's from that era pushed 150 psi per hole. If yours has high dome pistons in it, it is probably a bit tired.

look fwd to seeing pics thanks
conrad

[MercNuts]

The compression numbers you posted are very low for an inline Mercury. There are a number of things that can cause this including weak battery, inacurate guage, poor testing technicque or bad starter. It is good that they are uniform but if they are accurate and that low then the motor is extremely tired and will need to be rebuilt. It could indicate that it has been run hot damaging the rings or egg shaping the cyinders or just worn out from long use or poor oil or oil ratio. Some times the rings can get all stuck from oil over the years too and this can sometimes be fixed with sprays through the carbs without pulling it down. A leakdown test would tell you more.

These engines have never been described as 16 inch. The were called 15 inch for the transom height they were intended for or either simply as shortshsaft.

Unless you have a mechanic who works cheap changing your driveshaft as you mention in your other post on this engine is not the best option. It is not a good home project for someone who is not trained in gearcase repair and who does not have special tools. There are members on this board who can cut your driveshaft down in the standard length gearcase without removing it where it will bolt up to the 15 inch engine and that should not cost much over about 100 dollars plus the shipping.

It looks like your post here is worded different from when I read it a little while ago. Either my memory is bbad on what it said or it has been edited. As a little friendly advice if you are trolling around trying to find a buyer for it without registering it and putting it in the right forum it will start you off bad with the moderators here and you will see your posts start to vanish or may not even be able to get back in here in the future. I have seen it more than once.

[CAPTAINRICH67]

Hello Bama...
Thanks for the info. That is all appreciated. Not really sure what you meant by my post here being edited or different from when you read it a little while ago. I just got turned on to this site today, and have never posted to it before. I posted one in the tech section and one in this forum. Both, have not been changed or edited. Not really sure why you think there is a problem with my post. I want to learn as much about this engine, as I was told it was quite collectable. Maybe someday, after I get it all in one piece and sure it runs well...I will sell it. As for now...I would like to gain knowledge. Isn't that what forums like this are for?

[CAPTAINRICH67]

Thanks Milkdud....that helps. I was told that 120 was good compression...but that is for motors that are a lot less high performance. Being low in compression makes sense, as it has trouble starting and idling at low rpm. Once it is going, it screams. Seems like bad rings...and it may be a tired motor as I don't know the full history. Btw...I tried to post a pic today. Had trouble w/ it. I'll try again..or I can email one to ya if you are really interested in what the motor looks like.

[CAPTAINRICH67]

ok...just found out why you thought I edited my posting. Truth is that 'the admin' for this site, changed my post without my knowledge. My first post had asked if anyone knew what this engine was worth. I guess you can't do that. Not really sure why. But....it's their rules, so...anyway....no worries.

[MercNuts]

ok...just found out why you thought I edited my posting. Truth is that 'the admin' for this site, changed my post without my knowledge. My first post had asked if anyone knew what this engine was worth. I guess you can't do that. Not really sure why. But....it's their rules, so...anyway....no worries.

The reason is simple and it happens all the time here. When you start asking about value it implies that you are thinking about selling. The rules of this site are that if you wish to sell something here you have to be either be a regular participant first having 100 posts or more or register as a Team Member. If you go into one of the for sale forums these requiremtns are listed at the top. Almost every week somebody puts a post up about what is my boat or motor worth and gets offers to buy it which is going around the rules. A friend was told in a PM from a moderator that value posts are moved to the Buy and Sell Marketplace section or either removed based on a members status. According to the PM, recently another similar post was on the General Boating Discussion Forum here for a simlar motor and the motor sold so basically the newbie member got a free sale here and has not been back here since.

Tell the truth. Have you had any offers or interest in buying this from members here since you made the post? If the answer is yes then there is your reason.

[Mark Poole ModVP]

A boat that a 20 inch motor goes on will actually measure approx. 21 inches if measured ON the transom. That dimension turns into 20 inches when an outboard, with its angled transom bracket, is bolted to the boat. If you were installing a 15 inch motor on a boat and the cav plate were going to be even with the bottom then the transom would measure approx. 16 inches. However, a motor such as a 15 inch inline six merc would be installed on a 20 inch transom boat such as an Allison Craft and a racing (surfacing) prop used.

[gem56]

do you still have the short shaft mercury ?