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Author Topic:   Mercury 75 HP 4-Stroke

Barney posted 11-09-2003 06:50 PM ET (US)
We don't hear much about these engines.
While on the water today, I talked to a Department of Marine Resources law enforcement officer for about 30 minutes. Friendly conversation, he said my 11 foot Whaler looked a little small but nice. I wasn't in trouble. :)
On his heavy aluminum law enforcement boat was a 75 HP 4-Stroke Mercury. Basically the same as the 90 HP version. The engine had 850 hours on it and was just 1-1/2 years old. No problems and he loves it.
Jim
Barney posted 11-09-2003 07:24 PM ET (US)
I forgot, the oils, crankcase and lower unit, are changed every 120 hours.
Dick posted 11-09-2003 08:28 PM ET (US)
Barney
Interesting that you brought the Merc 75 4 stroke subject up.

I had a 16 Vetura with a Merc 75 4 stroke come in for winterization and storage last week. My outboard tech pulled the cowling and all numbers on the engine indicated that it was a 90, ran the serial number thru Merc and confirmed it was a 90.
No reason to change the HP on the cowling as the boat is rated for 115. The owner is out of town so I haven't been able to talk to him. My guess is that someone at the dealership screwed up and he got a great deal.
Dick
Moe posted 11-09-2003 08:40 PM ET (US)
What's the difference between a 75 and a 90? With the same block, bore and stroke, there's no reason the 75 torque curve couldn't be equal to that of the 90, up to some point where they want to cut the horsepower.
It wouldn't make sense from a manufacturing logistics standpoint, but if the 75 used smaller bore carbs and milder cams, it could even have MORE torque at lower rpms, than the 90, other things equal. But from an economic standpoint, I'd guess they use the same carbs and cams.
Cut back on ignition timing in the ECM at higher rpms?
--
Moe
John O posted 11-09-2003 08:44 PM ET (US)
Barney, I suspect the reason that we do not see much on the Mercury 75hp 4 stroke is the same as the Mercury 75hp 2 stroke which I purchased this spring. Before purchasing the 75hp 2 stroke I seached this site for previous posts on a 75hp 2 stroke and found few. I guess that in most cases when buying new, the 90hp is not that much more money and folks buy up. This was the case for me when pricing new 2 strokes. I assume the price difference in the 4 strokes are close as well.
In my case I bought a left over 2001 while shopping for a 90hp 2 stroke and saved a significant amount of money over current year models which were 2003's
Barney posted 11-09-2003 09:07 PM ET (US)
It had a different sound than my 90 HP 4-Stroke. But I know it's pretty close. The hours put on that engine with no problems say something about the reliability. Jim

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Author	Topic: Mercury 75 HP 4-Stroke
Barney	posted 11-09-2003 06:50 PM ET (US) We don't hear much about these engines. While on the water today, I talked to a Department of Marine Resources law enforcement officer for about 30 minutes. Friendly conversation, he said my 11 foot Whaler looked a little small but nice. I wasn't in trouble. :) On his heavy aluminum law enforcement boat was a 75 HP 4-Stroke Mercury. Basically the same as the 90 HP version. The engine had 850 hours on it and was just 1-1/2 years old. No problems and he loves it. Jim
Barney	posted 11-09-2003 07:24 PM ET (US) I forgot, the oils, crankcase and lower unit, are changed every 120 hours.
Dick	posted 11-09-2003 08:28 PM ET (US) Barney Interesting that you brought the Merc 75 4 stroke subject up. I had a 16 Vetura with a Merc 75 4 stroke come in for winterization and storage last week. My outboard tech pulled the cowling and all numbers on the engine indicated that it was a 90, ran the serial number thru Merc and confirmed it was a 90. No reason to change the HP on the cowling as the boat is rated for 115. The owner is out of town so I haven't been able to talk to him. My guess is that someone at the dealership screwed up and he got a great deal. Dick
Moe	posted 11-09-2003 08:40 PM ET (US) What's the difference between a 75 and a 90? With the same block, bore and stroke, there's no reason the 75 torque curve couldn't be equal to that of the 90, up to some point where they want to cut the horsepower. It wouldn't make sense from a manufacturing logistics standpoint, but if the 75 used smaller bore carbs and milder cams, it could even have MORE torque at lower rpms, than the 90, other things equal. But from an economic standpoint, I'd guess they use the same carbs and cams. Cut back on ignition timing in the ECM at higher rpms? -- Moe
John O	posted 11-09-2003 08:44 PM ET (US) Barney, I suspect the reason that we do not see much on the Mercury 75hp 4 stroke is the same as the Mercury 75hp 2 stroke which I purchased this spring. Before purchasing the 75hp 2 stroke I seached this site for previous posts on a 75hp 2 stroke and found few. I guess that in most cases when buying new, the 90hp is not that much more money and folks buy up. This was the case for me when pricing new 2 strokes. I assume the price difference in the 4 strokes are close as well. In my case I bought a left over 2001 while shopping for a 90hp 2 stroke and saved a significant amount of money over current year models which were 2003's
Barney	posted 11-09-2003 09:07 PM ET (US) It had a different sound than my 90 HP 4-Stroke. But I know it's pretty close. The hours put on that engine with no problems say something about the reliability. Jim