repowering with a 2003 Mercury Saltwater

[y not]

Am thinking of replacing a 1981 115hp johnson with a 2003 90hp merc 3 cyl 2 stroke. Any opinions if this is enough? It is going on back of 16'6" grp cuddy. I am told the 90 hp is measured at the prop as opposed to the Johnson measured at the head. Is this true? If so, it should be a good option I think.

 

[bryanredfish]

Re: repowering with a 2003 Mercury Saltwater

I have the 2002 Merc. 90. It's a great, surprisingly powerful engine. It runs a little rough at idle, but starts with ease, is relatively easy on gas (if you don't go WOT all hte time). It's been my impression that the 3 cyl. 90's have been among the most "bullet proof" engines out there.<br /><br />I bought mine new in 2002 because of the simplicity of design, and the past history of the motors. <br /><br />It is a very noisy engine, however!<br /><br />Good luck.

 

[Hooty]

Re: repowering with a 2003 Mercury Saltwater

You're givin' up 20+ hp. That's a bunch.<br /><br />c/6<br />Hooty

 

[y not]

Re: repowering with a 2003 Mercury Saltwater

Hooty, thats why I am asking. If the old johno is at the head verses the merc at the prop is there really that much differance? 2 local dealers say it is about the same maybe a little more power from a new 90hp.(one was a johnson the other a mercury dealer) They both suggest repowering with a 90 to achieve the same performance I already have, but I am not sure they are just not trying to sell me a new motor.

 

[Bob Kimber]

Re: repowering with a 2003 Mercury Saltwater

Y Not,<br /><br />Depending what sort of boat use you have in mind, I think you would be quite happy with the 90 merc. I run one on an old 17 ft half cabin Haines Hunter (79 model) 22 degree deep V which takes a few horses to go well, speed as tested using an aluminium 17" pitch prop verified by GPS is 28 mph @ 4300 rpm, WOT is 39mph @ 5300 rpm, I cruise around 4200 to 4400 rpm, quite good fuel use, around 19 litre for a trip of 30 miles to my favorite fishing spot at cruising speed or faster with some WOT.<br /><br />This engine replaced an inline six 90 merc and puts out a lot more power (WOT up by 6 mph) cruise at 4200 up by same, fuel usage down by about 33%. From about 4800 it really gets up and goes, passengers need to hang on.<br /><br />The motor does need some fine tuning (very sensitive to minor mixture changes on carbs)to suit individual boats to achieve a smooth idle, but once setup right will start first turn of the key, idle well and go well. I feel that it puts out more than 90hp after comparing it to similar boat and motor combinations I have been in over the years, as regarding noise, I feel it is better than most with only one particular noise band from about 4500 to 4700 rpm, it is surprisingly quiet at idle and up to 3800, increases slightly at the point previously mentioned and sounds great from 4800 to WOT.<br /><br />I think it would be more than adequate compared to the old Johnson and it is not a heavy motor at approx 140 kg (308lb), it has a lot more torque and 300cc more capacity than the 90 yamaha.<br /><br />regards<br />Bob

 

[y not]

Re: repowering with a 2003 Mercury Saltwater

Boating Bob, Thanks for the feedback especially from a fellow australian who will know of my boat.<br />It is a 1985 Cruise Craft Reef Raider 16'6" cuddy. Took out a 17 foot haines on the weekend with a merc 90 and was very surprised as it is a heavier boat with a deeper vee than mine. (650 kg with a 20 deg vee) It was very quiet at idle and only a little noisey in the high 4000,s. The dealer is suggesting a 18P prop which he says should give about the low 40,s mph at wot and about 25mph at 4000rpm which sounds good to me if accurate.

 

[y not]

Re: repowering with a 2003 Mercury Saltwater

What an improvement<br />5300 at wot & 42 mph<br />4000 cruises at 25 mph throughing a 18p stainless and a hell f a lot lighter then the old Johnson I had. Not noisey at all idles well and starts easily. **** good, quick and quality job by my local mercuray dealer. Woohooooo am looking forward to lots of happy hours

 

[Bob Kimber]

Re: repowering with a 2003 Mercury Saltwater

Y not,<br /><br />Good to hear about your new motor, I think you will be happy with it, you didn't mention if it was a new motor out of the box or a traded one. If it is new, you won't see top performance till you have done about 50hrs, these motors seem to take a while to run in. The 18p SS prop is approx the same as a 19p aluminium prop in performance, what load was in your boat on the test run? Mine loaded for fishing with full tanks, eskys, gear and passengers (estimated weight 2700lb - 1228kg) is just a little low in rpm at WOT with the 18p ss (5150) and too high with the 16P ss (5750) so the 17p aluminium performed the best at 5300 fully loaded and a full length bimini top (from windscreen to transom).<br /><br />Mine is a 2000 model and continues to get better as it accrues hours, there are quite a few 75 and 90 hp mercs (same motor) in this area including the original 1988 models (the first models) still running strong with no major problems noted apart from normal wear and tear and servicing<br /><br />Bob

 

[y not]

Re: repowering with a 2003 Mercury Saltwater

Bob, It is brand new out of the box 0 hours running.<br /><br />Those figures given were the "on water test" with the dealer trying to get the right prop size selected.<br /><br />Load was two up with full fishing gear and fuel. The boat was loaded as I was just coming to the end of a 2 week camping/fishing trip around the Jumpinpin area whjen the old Johnson started to play up.<br /><br />it bogged down a little coming home carring all the camping gear and 4 people it dropped to about 5000 rpm wot. But, as that load is a rarity not the norm I think thats ok.<br /><br />Trevor