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Author Topic:   Mercury 90-HP Four-stroke

kline posted 11-21-2006 10:41 AM ET (US)
I am in the process of buying [ a 2005 Mercury 90-HP Four-stroke] and would like some feeback on the engine's performance.Thanks,
Steve
Barney posted 11-21-2006 08:22 PM ET (US)
Steve, You may have to do a search for alot of info on that outboard. Some have carbs some have EFI. But in general if it's EFI it will be an ok. If it has carbs, which I don't think it will, take a pass. Jim
bigjohn1 posted 11-21-2006 08:56 PM ET (US)
If it has EFI, buy it with confidence and enjoy. If it has carbs, there is a chance you will have carb problems from them gumming up. If you lived in hot weather and boated year-round, the carbs would likely be less problematic.
kline posted 11-21-2006 08:56 PM ET (US)
Barney,
Thanks for your reply. It is an EFI.
Steve
jimh posted 11-22-2006 07:48 AM ET (US)
There have been several reports of chronic problems with the carburetors in the Mercury 90-HP four-stroke outboard motor, however, I do not recall any complaints about the fuel-injected version of the engine.
edfish posted 11-24-2006 02:24 AM ET (US)
I find this thread very interesting in that I own twin 70-HP Mercury (by Yamaha) four-stroke outboards. They are model-year 2000 with carburetors. In the over 3,500 hours that I have run them, I have not ever had a problem with the carburetors, or anything else, except for the gasket recall early on. I will admit that my engines do not sit for very long in the Winter and never in the Summer.
I always use a fuel additive like Mercury Power Tune, Sta-bil, or Lucas top end oil and cleaner in the fuel.The Lucas is nice in that it really makes them run sooo smoothe.
I have a Mercury water separator fuel filter that I change several times a year. Very cheap insurance in my opinion.
Actually, I just remembered that I need either a new rectifier or stator on the starbord engine. I have not had time to test for what I need yet, so I just rely on the other engine and have no problem keeping my group 30 AGM batteries at their peak.
I love those engines and they have brought me home in many very nasty situations.
I know that you are talking 90-HP, but they are the same block [as my engine], as far as I know. I would not worry [about] either one of the fuel types, carburetor or EFI.
Good luck and the best to all.
Ed Tavas. F/V Friendship. 1972 21' Outrage
bigjohn1 posted 11-24-2006 05:24 AM ET (US)
edfish: The topic of Merc 90 4-stroke carb problems comes up from time to time here. Several have chimed in saying they have experienced carb problems. While I have not been collecting any hard data regarding geographic region and useage pattern, the majority of the problematic engines seem to come from the following situations:
1. Owners with short boating seasons and long winterization periods.
2. Owners who left un-stabilized fuel in their engines for the winter layup.
3. Owners who run straight gas with no additives.
It is my belief that Mercury fitted this particular engine with tiny jets in the carbs to attain the 3-star emision standard and this fact seems to make the engine very sensitive.
While I don't personally own this engine, we have a huge Merc dealer locally and many, many local boats have this engine without problems. It must be said though that we have a year-round warm boating season. I make this observation from discussion with boaters I encounter at the local marinas when launching the recovering and from talking with my local Mercury mechanic. I know of only one such engine with these carb problems and this was on a boat which was stored outside and uncovered for many months at a time between uses.
I personally think any owner of this engine who follows your advice will absolutely minimize any problems with the Mercury 90hp 4-stroke (with carbs). That said, if the boat lives up north with a 3-month boating season, all bets are off.
jimh posted 11-24-2006 09:07 AM ET (US)
It is hard to draw an accurate impression of the overall utility of a particular motor based on a collection of anecdotal reports about it, and, the impression can be especially inaccurate when you accept that notion that people who have had problems are more likely to post complaints than people who have not had problems are likely to post spontaneous citations of satisfaction. But even given that allowance, there have been quite a few mentions of problems with the carburetors on four-stroke motors in the 90-HP range, and particularly so with the Mercury motor, and I think there have been enough to be worthy of mentioning them.
I agree that the problems cited may be related to a pattern of use where the motor has been left in non-use for long periods.
There has been a great deal of discussion in the past about the general benefit of an electronic fuel injection (EFI) system as compared to a carburetor system. My conclusion is that the principal benefits of EFI are:
--the fuel system is not directly vented to the atmosphere and therefore it is not prone to problems due to fuel evaporation as occurs in a carburetor.
--in colder weather conditions a sophisticated EFI system can produce enhanced starting and running during the period of engine warm-up as compared to very simple carburetor systems.
Proponents of EFI have tried to ascribe many other advantages to them as compared to a carburetor, however, in situations where a boat is likely to be run, i.e., at sea level and in moderate temperatures, I do not believe there is a huge difference in performance.

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Author	Topic: Mercury 90-HP Four-stroke
kline	posted 11-21-2006 10:41 AM ET (US) I am in the process of buying [ a 2005 Mercury 90-HP Four-stroke] and would like some feeback on the engine's performance.Thanks, Steve
Barney	posted 11-21-2006 08:22 PM ET (US) Steve, You may have to do a search for alot of info on that outboard. Some have carbs some have EFI. But in general if it's EFI it will be an ok. If it has carbs, which I don't think it will, take a pass. Jim
bigjohn1	posted 11-21-2006 08:56 PM ET (US) If it has EFI, buy it with confidence and enjoy. If it has carbs, there is a chance you will have carb problems from them gumming up. If you lived in hot weather and boated year-round, the carbs would likely be less problematic.
kline	posted 11-21-2006 08:56 PM ET (US) Barney, Thanks for your reply. It is an EFI. Steve
jimh	posted 11-22-2006 07:48 AM ET (US) There have been several reports of chronic problems with the carburetors in the Mercury 90-HP four-stroke outboard motor, however, I do not recall any complaints about the fuel-injected version of the engine.
edfish	posted 11-24-2006 02:24 AM ET (US) I find this thread very interesting in that I own twin 70-HP Mercury (by Yamaha) four-stroke outboards. They are model-year 2000 with carburetors. In the over 3,500 hours that I have run them, I have not ever had a problem with the carburetors, or anything else, except for the gasket recall early on. I will admit that my engines do not sit for very long in the Winter and never in the Summer. I always use a fuel additive like Mercury Power Tune, Sta-bil, or Lucas top end oil and cleaner in the fuel.The Lucas is nice in that it really makes them run sooo smoothe. I have a Mercury water separator fuel filter that I change several times a year. Very cheap insurance in my opinion. Actually, I just remembered that I need either a new rectifier or stator on the starbord engine. I have not had time to test for what I need yet, so I just rely on the other engine and have no problem keeping my group 30 AGM batteries at their peak. I love those engines and they have brought me home in many very nasty situations. I know that you are talking 90-HP, but they are the same block [as my engine], as far as I know. I would not worry [about] either one of the fuel types, carburetor or EFI. Good luck and the best to all. Ed Tavas. F/V Friendship. 1972 21' Outrage
bigjohn1	posted 11-24-2006 05:24 AM ET (US) edfish: The topic of Merc 90 4-stroke carb problems comes up from time to time here. Several have chimed in saying they have experienced carb problems. While I have not been collecting any hard data regarding geographic region and useage pattern, the majority of the problematic engines seem to come from the following situations: 1. Owners with short boating seasons and long winterization periods. 2. Owners who left un-stabilized fuel in their engines for the winter layup. 3. Owners who run straight gas with no additives. It is my belief that Mercury fitted this particular engine with tiny jets in the carbs to attain the 3-star emision standard and this fact seems to make the engine very sensitive. While I don't personally own this engine, we have a huge Merc dealer locally and many, many local boats have this engine without problems. It must be said though that we have a year-round warm boating season. I make this observation from discussion with boaters I encounter at the local marinas when launching the recovering and from talking with my local Mercury mechanic. I know of only one such engine with these carb problems and this was on a boat which was stored outside and uncovered for many months at a time between uses. I personally think any owner of this engine who follows your advice will absolutely minimize any problems with the Mercury 90hp 4-stroke (with carbs). That said, if the boat lives up north with a 3-month boating season, all bets are off.
jimh	posted 11-24-2006 09:07 AM ET (US) It is hard to draw an accurate impression of the overall utility of a particular motor based on a collection of anecdotal reports about it, and, the impression can be especially inaccurate when you accept that notion that people who have had problems are more likely to post complaints than people who have not had problems are likely to post spontaneous citations of satisfaction. But even given that allowance, there have been quite a few mentions of problems with the carburetors on four-stroke motors in the 90-HP range, and particularly so with the Mercury motor, and I think there have been enough to be worthy of mentioning them. I agree that the problems cited may be related to a pattern of use where the motor has been left in non-use for long periods. There has been a great deal of discussion in the past about the general benefit of an electronic fuel injection (EFI) system as compared to a carburetor system. My conclusion is that the principal benefits of EFI are: --the fuel system is not directly vented to the atmosphere and therefore it is not prone to problems due to fuel evaporation as occurs in a carburetor. --in colder weather conditions a sophisticated EFI system can produce enhanced starting and running during the period of engine warm-up as compared to very simple carburetor systems. Proponents of EFI have tried to ascribe many other advantages to them as compared to a carburetor, however, in situations where a boat is likely to be run, i.e., at sea level and in moderate temperatures, I do not believe there is a huge difference in performance.