Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercruiser

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

I went through this exact evolution in 2007. I had the 470s on my 25' Kingfish (in '83 a Kingfish was a Sailfish with an I/O) and the time had come to repower. I wanted to go with twin sixes too but found out the same thing you did. They would not fit without a lot of mods. I had contacted Grady back around 1995 and had spoken with them about suggetions for repower. The gentleman I spoke with then said that in his opinion the 260 HP models were "kind of doggy" but the ones powered with a 454 were very nice. I thought long and hard about the twin 135s and found that many of the older Bertrams repower with these motors, as a matter of fact my neighbor repowered his 26' with these motors. They seem to run them with a four bladed prop, you would find info about the twin 135 repower on a classic Bertram site. I spoke with the tech that was going to do my repower at length and his opinion was the 135s would work but you would be running them at high rpms all the time. Makes sense to me as I was running 340hp and you 360, 270 horse seems to me to be a large decline in HP. I started to think about a single and in the end went with a 496 Mercruiser/Bravo 1 and am VERY happy with the result. It fit with a minor modification to the front of the motor box. I have run this package a few seasons now and like everything about it. If you are happy with your boat as I was I think the repower is worth it. I enjoy the HP, I don't think I would have been happy with the twin 135s but my repower did cost more than $10,000 too. Many suggested I purchase a newer used boat and go with that but everything I looked at in the price range had at least ten year old outboards, many older. I liked my I/O and wanted new power not someones elses problems. This was before the ecconomy took the big dive so prices were different then but that was my experience at that point. Of course my repower at this point in time might cost less also.

$10,000 is pretty reasonable but how much more would the the package cost with new drives too? Are you going to do the work or have it done? When they did mine I had to have the transom redone so have that checked well before you make your decision.

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

If you can fix for $10k and can handle having what basically will be a displacement hull due to the lack of power to get up on plane, go for it. When I was looking for a Sailfish back in 1994 I sea trialed a few 260 HP boats but found that they struggled to get up and go.

I ended up buying a 1988 Sailfish 330 HP OMC King Cobra 460 CI. It was ok but still was like a concrete mixer to get moving. It delivered a fuel economy of about 1.2-1.4 NMPG. Max speed about 30 Knots.

In 2001 faced with a variety of maintenance issues and the fact the the motor was basically an orphan as far as parts availability, I sprang for a Mercrusier 496CI 375 hp Bravo III. It wasn't cheap probably better than $25K installed with props today but well worth it if you love your boat and plan on keeping it a minimum of five years.
The results were fuel economy of 1.8 NMPG at 20 knots and the ability to blow off the Formulas and twin outboard Grady Sailfishs when they try to race by you heading for the harbor.

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

I fished many days on Lake Ontario as a first mate in college on a 1983 Trophy Pro with a single 260 OMC. The boat was a real dog esp with 6 people on board and could be downright scary in a following sea. Numerous blown outdrives as well trying to push a heavy Grady Hull with a single screw. There were many captains running 23-25' Sea Rays as well with single 260 mercruisers experiencing the same outdrive issues as the OMC. The Bravo drive has cured the issues that the Alpha drive had in handling the rigors of a big heavy boat. I see many 28-30' daycruisers at my marina on Lake Ontario with single Bravo drives, so I have no doubt that a repower to a big displacent 350+HP V8 would work fine in your boat.

That being said, My dad purchased a new 1986 Sailfish with twin 470's and I am still running that boat witht the original engines, likely 2500 hours on each now, mainly trolling. So, I understand that everyone has their own opinions on the 470's, they are far from perfect, but your boat is setup for them, new blocks and many parts are still available, why not repower with rebuilt 470 blocks and keep it easy on yourself?

To me the biggest selling point is the security of having twin engines versus being locked into a single and being stuck many miles from shore...

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

upgrady I too enjoyed my 470s and looked into replacing with the same engines etc. I had done most of my own work on them over the years and knew them well but I had tired of the process. In addition after 23 years in salt water I wanted to have new "everything" front to back, Motors drives and intermediate housings. After looking into it I went with the modern single and I have to say I really enjoy the new technology and the lack of issues. Perhaps the largest inprovement for me is the shifting with the Bravo compared to the Alpha. In the end I just figured that the 470/alpha platform was develped in the late 70s and I was interesed newer tech. For me it was the right choice for others perhaps not.

If the OP goes with the 135s I would like to hear performance numbers etc. When I was thinking about it several people mentioned the rating system is more conserveative now then back in the 70s. Perhaps the 170hp to 135hp difference per motor is not really 35hp but something less. Mine is the 375 hp 8.1L but it feels like I have added more than 35hp to the boat. Granted I have one less drive in the water and I think the weight is about the same as before. The 8.1L feels lighter and the boat rides more on top than before. I did enjoy the 470s for years - it was just time to replace and reap the rewards of 30 years of developement.

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

Jeff,

Good information... I am certain that I will need to be making similar decisions in the near future. Although I am only putting 70ish hours per year on each engine and only need to run about 8 miles to begin fishing on any given day, the hours and age will catch up with me soon... So, if I may ask, there were only minor mods needed to the doghouse to fit the V8 in place of the twin 470's? I would be interested in seeing photos of the mods if you have them available for posting.

Thanks,
Hans

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

Hans - The boat is under cover for the winter but at some point I will get out there and try to get a couple of pictures. On the dog house the only obvious mod was I lost the rod holder rack that is recessed in the front center of the dog house. The intake on the motor would not clear. They cut out the center area out of the front of the box and put a Starboard panel there. Looks fine and not cobbled together. The other mod was the in the deck area forward under the dog house. They needed an inch more room from front to back. They removed the wood trim piece, that rings the motor well area, at the front and cut the deck out and reinstalled the wood piece with a spacer on the side pieces. They did not need to change the dog house at all as the extra inch was available, just had to remove some deck. This past spring I removed the cup holders in the dog house and installed a couple of gunnel mount rod holders in their place as I missed the factory rod holders. I don't use them for trolling but like to put rods there when I am getting on the boat and running to the fishing area. I am going to redo the wood panel on the rear of the cockpit this spring and need to get some sort of holder for my pliers etc. as I used to keep those in that center rack too. I just need to find a place where I won't be running my knee into it. All in all the motor fit fine in the space available. I'll try to get some pictures for you.

I take you point about liking the 470s. I did too but in the end I figured it would be like looking to repower an outbaord powered boat with some rebuilt late 70s motors. Everybody has different ideas but the big block has worked well for me.

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

Great Stuff there! My 87 254 was originally powered with the 260 but had just been repowered with the 300 when I got her. The 300 is no speed demon but it will maintain a good plane at a conservative power setting. The 496/375 would be my choice for the best upgrade. Building up a couple of 180 replacement engines would be my next choice. If I already had 135's I would cetainly use them. 8)

Ken

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

Ken yours was one of the motors I looked at too. What are the particulars of performance with the 300? Best cruise and GPH etc.

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

Out of curiosity, why are the "470s" non rebuidable? My understanding is they are basically 1/2 of a Ford 460 block, using stock Ford pistons, rings, heads, etc. If your block and crank are reusable, they should be able to be rebuilt, and for a lot less than $10,000. I also had a 25' Kingfisher with twin "470s", and I loved those engines. Good power, economical and dependable, all in a small package. Just my opinions, Mike.

rwbaran said:

Need advise please
I need to replace the twin 180 hp.4cyl. mercruiser motors (non rebuildable) the alpha drives are in good shape,I researched mercruiser 190 hp. V6's dimensions and found that major modifications would have to be done and would not be feasable. The only mercruiser that will fit is the 135 hp.tks 4cyl. Has anyone done this before,if so what was the performance?
Grady White offered (single engine package) a 260 hp. mercruiser for trophy pro and sailfish models which are similar in weight, since I will be using two 135 hp. motors for a total of 270 hp. I think the performance will be similar to that of a single 260 hp. 25 foot grady. Can anyone who owns a single 260 hp. grady tell me the performance of their boat?
I checked the price of installing a gil bracket and two outboards and found the sum to be in excess of $30,000.
The price of installing two 135 hp. mercruisers (utilizing original alpha drives) is less than $10,000 total.
I would appriciate any information or advice, thanks guys

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Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

My 254 with the 300hp 350 Mercruiser/Bravo II seems to cruise best for me at around 3200-3400 rpm. Speed at this power setting is usually around 22-24 mph with an average fuel burn of around 6 gph. My boat weighs in at about 5500# empty weight. The little 350 is a very sweet running engine with adequate power and pretty good fuel economy. Does anyone know of any boats running the Mercrusier with the Cummins diesel engine. 8)

Ken

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

That is very thrifty. I tend to cruise at the same RPM range but run about 26 knots. Of course I am using more fuel too. That engine of yours seems to be a nice combination with your 25.

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

I have a 1988 sailfish 254 that i repowered with twin mercruiser 3.0 mpi with alpha drives. Performance is rather good she will cruise at 23kts at 3600 rpm with 4 people onboard with 120 gals of fuel top is around 33kts at 4650 rpm. The drives are 2.0 ratio with 14x19 4 blade props it jumps on plane quicker than it did with the mercruiser 470

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

rn571975 said:

I have a 1988 sailfish 254 that i repowered with twin mercruiser 3.0 mpi with alpha drives. Performance is rather good she will cruise at 23kts at 3600 rpm with 4 people onboard with 120 gals of fuel top is around 33kts at 4650 rpm. The drives are 2.0 ratio with 14x19 4 blade props it jumps on plane quicker than it did with the mercruiser 470

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Sounds good, do you have any fuel numbers for WOT and cruise?

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

With the mpi engines fuel she burns around 10 gph an hour at wot 23gph I am very pleased with the engines they have just over 300 hrs on them now and not aminautes trouble out of them

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

My 254 with the 300hp 350 Mercruiser/Bravo II seems to cruise best for me at around 3200-3400 rpm. Speed at this power setting is usually around 22-24 mph with an average fuel burn of around 6 gph. My boat weighs in at about 5500# empty weight. The little 350 is a very sweet running
engine with adequate power and pretty go
od fuel economy. Does anyone know of any boats running the Mercrusier with the Cummins diesel eng



Just wondering what size prop your running?

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

jbf8728, How's it going? Just happened to notice this oldie but goodie post had awakened. Us inboard/outboard types are the exception these days. I am running a pretty good size prop with my MPI 350. It is an 18-3/4" diameter X 19 or 19 1/4" pitch. I have never exceeded 4800 rpm but it still has a good bit of throttle left at that power setting. I rarely ever exceed 3400 rpm which gives the 22 to 24 mph speeds. 8)

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

Hello Jumpnjacks. Thats some pretty good performance with the bravo drive. especially the gph. with my alpha gen 2 i burn 13 gph at 3400 rpms at about 20-21 kts. my prop is a 15x15.5 turning up 4600 rpms. I guess the outdrive makes the difference? Thanks the reply

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

jbf8728, the average of 6 gph is based on a 12-14 hour offshore trip. I would imagine that the rate of 9-10 gph while at cruise power might be a good flow for that power setting. The little 350 is a sipper at those lower power settings. We stop and fish in quite a few places in the course of the trip also. I usually burn around 70 gallons on one of these typical days which leaves me still holding 55 gallons. I believe the Bravo II is geared at 2.33-1. What is your engine and gearing? Based on your engine versus prop rpm it looks like you are geared differently than the Bravo II. 8)

Re: Repower 1988 25 ft. Grady trophy pro twin 180 hp. mercru

I have a 1981 Grady White Wahoo 256 with a 454 straight inboard. It has a 1.72:1 Borg Warner gear and 16" prop. I get around 1.5 gallons per hour at around 3800 rpm. Speed in that range with boat averagely loaded in freshwater is around 27 knots.

Like I said though, this is a straight inboard, not an inboard outboard.