Some advice for first Maxum owner 97 2700 scr

[JrJ01]

Hello, I am new here, first post, glad to have found this site!

I just bought a 97 2700 scr, 7.4 bravo II
I was not able to get an actual sea trial on the boat due to the particular issues of the sale, however I got this
boat on a trailer for a very low price. Its very clean and I am the 3rd owner. The 2nd owner had it for one year and
due to life situations had to sell it, used it a couple of times at most..

At this point I am less than satisfied with my great deal, but again got it for a price that I can actually afford to upgrade and take
care of issues.

No knocks, no ticking, very sound, no leaks cleanest engine compartment I have ever owned.. clean oil, starts right up everytime no problems..

so its running consistently around 180 degrees, climbs up maybe to 185 at times but goes back down..is this the correct
operating temp of this set up? My last boat with 7.4 bravo 1 was 150 -160 so I am thinking its running hotter than it should.. I thought that most marine thermostats were 160..

this boat is really hard to get on plane. the most I got out of it was maybe 30mph and I am afraid to say the RPMs it took to get it there assuming the guage is reading correctly..
I thought this boat being alot lighter than my last single engine 7.4 and having a newer engine, lower hours etc.. would hit at least the mid 30s if not upper at a reasonable RPM at WOT
of course basing this off my last 30ft boat weighing almost 1000 pounds more and much older..that easily gets 40 mph and on plane in a relatively short time..

I will replace seawater impellar this week to see how that goes.. is there an impellar in the outdrive as well on the bravo 2?
The prop is apparently the stock prop.. alum.. not sure of size but am told it is the stock prop. I can at this point afford to replace the lower unit on the drive and was thinking of going to a bravo 3 lower I am reading that the lower is interchangeable on Bravo drives.
Any thoughts on this?

I am looking to get the boat running a little more than 30 mph.. if this is all this model can do, I think the for sale sign is going on it
Its a beautiful boat and very clean but am used to being able to cruise at 28 to 30 not WOT .. so its pretty disappointing, but, was the risk I took on it.. hopefully someone here will have some good information.. I am not a marine mechanic.. can perform simple projects like impellars and pumps etc.. but do not know the details and specs that many here seem to know.
Thanks!! I hope this is of interest

[pascavone]

hey Jr sounds like my story 3 years ago, with receipts with a new engine and bravo III drive.

but, i had a electrical short, bad engine coupler, broken trim tab hinges, leaking toilet tank, and a smoked raw water pump.

my 28scr will go about 38mph and plans fine with trim tabs.

So,

raw water pump.... check.
engine couple..... stick your head back behind the motor and look for rubber grinding or aluminum grinding.
trim tabs... stick your hand under the water, with the engine off and have someone run the switches out.
my original carbon monoxide detector was shot and drawing too much juice, so that what was killing the batteries.
main transom pin seal was shot and dripping, look for white salt trails down the inside transom.
check your manifolds.... if they leak then the engine will get soaked.

[mmwjr]

JR I agree with Pas the boat should do better than 30 mph. How many passangers were on board? What was the rpm? Pull prop and check the part number to find pitch and diameter.

180 is a little hot. I would get a handheld IR thermoter and measure the manifolds and therostat housing as guage can be wrong. Replace the impellar and t-stat. You may want to pull risers and inspect them as well.

A B3 lower end will bolt to a B2 top end but not sure this will help top speed.

[cdhunter]

JR - My 1997 2700 SCR w/7.4 & BII will do 34.9 kts @ 4200 RPM on the GPS with the fuel and water tanks topped off and (2) adults on board. The engine temp usually runs between 150 and 160.
Congrats on your new boat and post up some pics when you get a chance.

[SRPATTON]

My 03 2400SE w/ carb. 5.0 runs 35 mph (31 knts) @ 4200 RPM. Put 6 people on it and with full tabs down it's a real dog on planing. Temp gauge was reading 190 but the IR gun shot the t'stat @ 160. Changed the gauge and they matched.

[JrJ01]

So I realised my prop was missing the diffuser ring? might this be the problem? I took it to a propeller service shop locally and he is convinced it is.
Wont have the prop back til Friday.. any thoughts on that?

Thanks for all the input and help on this!! I havent had time to do much since the post because of work.. but I am going down the check list above

[mmwjr]

I had this happen on my last boat and the result was the prop would blow out (lose bite) under load. In my case it was a brand new prop that failed so I was able to get a new one and that fixed my problem.

[JrJ01]

Got the reconditioned prop on the boat.. it seems to run a little better.. gets on plane much easier
still no top end speed comparable to others with this same boat and set up... top WOT 28/29 mph 46-4800 rpms
the prop is a 19 pitch, I have a 23 pitch for it, might change it out but dont think it will help top end other than maybe
slow the rpms.. hmm...

[mmwjr]

Going from a 19 to a 23 pitch prop will bring the rpms down and the top speed with it, however bottom performance (time to plane) will improve. How are you measuring the boats speed? Onboard speedo? If so it may be off, most smart phones have a gps function that will allow you to measure ground speed so you may want to try that and compare. Is the bottom and outdrive free of marine growth? How many people were onboard? No reason this boat should not be able to break 30 mph with ~4 people, fair seas.

[JrJ01]

Hi Mike, I use my gps on my phone.. checked it against my wifes gps on her phone.. the onboard speedo seems to work and then not.. the bottom is painted and clean, the drive is free of all debris..
I just launched this boat when I originally posted. It was just me and wife , 3/4 tank of fuel.. I am thinking there is something wrong obviously.. if I was loosing compression would I still get high rpms? Local boat shop says might have a cylinder or cylinders with low compression? The opertaing temp has stabilized at 175-180 no higher.. I am pulling it out this weekend and leaving it at the shop til they can get a look at it.. its been a bummer though.. going from a 1987 30 foot boat 1000 pounds heavier.. same motor with bravo 1 drive that easily handles the river at a good clip.. to a smaller lighter boat newer engine bravo 2 and cant get itself moving.. I talked to a previous owner and hes says 30 the max he ever had on it.. will see what the shop has to say, thanks for the feedback!!!!

[mmwjr]

JrJ01, best of luck and report back on the findings from the shop.

[1994Maxum2700SCR]

Hey Jr,
I have a 1994 2700 SCR with the 7.4L and bravo 2. My boat with full water and fuel and about 4 people on board running a 19" pitch cruises around 3300 RPM at about 16 knots (18mph). WOT is around 4600 RPM and hits about 30 knots (34mph).
I forget my readings with the 21" pitch prop but top RMPs were only about 4200

Hope that helps,
- Joe

[JrJ01]

Took the mechanic out on it yesterday.. gonna pull it out this weekend it looks like.. the engine is performing
well. The timing is on.. compression good.. carb could use an overhaul but did a good cleaning while there.. so boat is running as it should and the
engine is strong.. so we get it out.. and it dogs as usual, he's telling me to trim it out.. I tell him I am.. its all it does.. so he then says this
boat feels like its pulling an anchor behind it.. so I am not halucinating.. says it has to be the outdrive.. we know its not the prop both are reconditioned..
says the lower unit may not be the right gear ratio for the boat if it was ever changed out,
does this sound reasonable? trying to find out what gear ratio this boat should be now.. engine OK166682 drive OK184680
calling around today

[1994Maxum2700SCR]

I think the gear ratio for our setup is 2:1.

[CountryME]

According to maxumcustomercare.com your 2 7.4l engine options for that boat were:
ET6 OPT. 300 M C/B2 (7.4L) 1.81:1
or EP9 OPT. 300 M C/2 (7.4L) 2:1

I know my sport boat is a different animal, but the engine and outdrive numbers match on mine. Any chance the previous owner cleaned off the original leg and replaced it with the wrong one? The mechanic's idea has great potential.

[JrJ01]

Hello thanks for letting me know!! still not sure what boat I have but I think its the 1.81 ratio. is there somewhere I can look on the boat to tell?
I am thinking that yes at some point the lower drive was replaced with the wrong lower.. so, I bought a full 1.81 geared upper and lower drive off my local
craigslist today.. gonna see if that works out tomorrow. I just hope mine is not the 2.1 engine..

[mmwjr]

Jr, buying another drive is a costly experiment. The ration of 2:1 means that for every 2 revolutions of the drive shaft (input to out drive) the prop shaft will rotate 1 time. If you have the wrong drive another way to tell would have been to try props with different pitches, while this may not yeild the best solution it is an easier way to determine if the performance will improve before changing drives. I would assume your mechanic would be able to provide some used lender props for this.

To see what ratio you have but a half inch drive on the crank pulley bolt and turn the engine clockwise 2 revolutions and have someone watch the prop to see if it make 1 revolution if so it's 2:1 if theprop makes more than 1 revolution that 1.8:1.

Good luck and keep us posted.

[JrJ01]

Thanks Mike!!! heading out to check today.. I have the new drive upper and lower complete for $750 with a 19p prop on it .. this prop is rated for the 1.81 gear ratio according to the maxum site that CountryME recommended.. this drive unit is a mercury marine reconditioned complete drive that came off a 28ft Rinker same engine I am told. The story behind this drive is that the father of the kid who sold me it bought it reconditioned before he got sick and eventually passed away.. the boat never got done so he is parting it out. Today I should have some news..

[CountryME]

JR, make sure you are getting what you need. http://bluewatermarinesvc.com/html/mercruiser_fyi.html lists info on how to tell that gear ratio the drive leg has inside it.

[mmwjr]

Jr, thisboat is no pocket rocket but if you are looking for a nice cruiser that will run low to mid 30's this boat should do the trick. What Country provided will definitely help. Only caution is ifthe unit is rebuilt there is no guarantee that the same gears ratio was used, hence my recommendation to check as I outlined in my last post.


BTY: It may help to make a chaulk mark on the crank puller at 12 o'clock and across th prop hub to outdrive housing as reference points.