Big Block in a 23' Tsunami ?

abl1111 · #1 09-09-2003, 03:29 PM

As many of you know, I am re-doing a '75, 23' Tsunami. Transom is done.

The conversion from (2) i/o's to (1); new motor beds and bulkhead are in. Old i/o holes structurally sealed ( not cosmetically yet ).

I am starting to think about which motor to put in - not to mention the drive. A book can be written about the different opinions of which drive to use !!!

I was leaning to the Mercruiser Horizon 5.7 - 300 HP. Would anyone recommend going larger, like a 454 ? Remember - the boat had (2) 4 cyl's in there originally... Any opinions here; pros and cons ?

Thx

gss036 · #2 09-10-2003, 12:50 AM

I would stay away from the GM motors. They have a real problem with piston slap. I have one in my new truck and they rebuilt the engine at 11000 miles, didn't stop it and at 15000 dropped in an out of the box factory engine. I now have 31000 on the truck and I am startting to get the slap back again. I have hear this story over and over and personally know of 3 friends who have had the same problem. Check the GM forums and read all the misery stories, a lot like the 1st stories on Mercury OPTIMAX's. GM now say's it is normal and will not do anything with the engines even though they slap. Sounds like a stuck hydrolic lifter on a cold start-up.

TUGBOAT · #3 09-10-2003, 06:03 PM

Gary,Take Your GM Truck back to the Dealership or another ,let them verify this condition (Must have proof) Then call 1-800-222-1020,at that point they(gm) will extend Your engines warranty to 1000,000 miles.They were doing engine replacements/changing to teflon topped pistons etc.Which neither fixed.There have been No real failures because of this problem.Just a Pain in the EARS !The warranty will only be applied to direct results of the clatter condition.Not bad /low oil etc.
A Siren told Ya this whilst fishing in the Fog !!
Scream'n reels'

gss036 · #4 09-10-2003, 08:48 PM

I managed to get the WARRANTY extended out to 5 years/60,000 wirh a letter from GM. If it gets where it is consistant I will definately get it back in before the 5 years are up. I don't drive enough to hit the 50k.

TUGBOAT · #5 09-10-2003, 11:31 PM

Gary Maybe Your area(NorthWest) is diff. from southEast(Warrantys).There is a 100,000 mile No Years attatchment.Maybe Your 31000 miles is added to the 60,000 which comes to 91000 .close enough?
It'll last that long ! [img]images/icons/cool.gif[/img]

John R · #6 09-11-2003, 08:53 AM

You guys are scaring the crap out of me, my 4.8 has had a "lifter" tap from time to time - I got 10K on it [img]images/icons/mad.gif[/img] - I knew some of the Fords had some piston slap, especially the Hi-Po motos )Lightening, Harley) but I'd just started to hear about the GMs

[ September 11, 2003, 07:55 AM: Message edited by: John R ]

ScottM · #7 09-11-2003, 10:21 AM

Alan,
Hopefully Chris Downey can give you his $0.02 on the subject. He's got a 454 in his Sceptre (sweet boat [img]images/icons/smile.gif[/img] ).

Water Rat · #8 09-11-2003, 11:08 AM

Alan:

My apologies for not responding to your post sooner - seems I always get interrupted every time I log onto ClassicSeaCraft.com. Also, Scott, thank you for your kind words.

I repowered my boat in 1989. Went from a single, old OMC 230hp V8 with the lousy OMC outrive to a MerCruiser 7.4 litre (454 c.i.) block, 330 h.p., with a Bravo 1 drive. At that time the Bravo 1 had been around about 2-3 years. Here is my list of pro's and con'son this set-up.

Pro's:
Though some may disagree with me, the installation is not all that tight. I do most of my own maintenance work, and only really wish I had better access to the bottom end of the motor (starter, plugs, etc.). Access to front, rear, and top is generally good, and should be especially so in your boat if you maintain the original cut-out for the twins. As for performance, at a 3000rpm cruise, light boat, calm conditions, I get approx. 24 knot cruise and 36 knot top. 3500 rpm will give 26-28 knot cruise in those conditions. I do not care so much about top end, but comfortable cruise and plenty of torque. Compared to my first motor, performance in that area is night and day. However, I still wish for more torque when riding the back of a large following sea. I am very pleased with the Bravo 1 - little to no cavitation, and boat responds well to trim adjustments. The boat is relatively fuel efficient; with my 2 tanks totaling 110 gallons, I get about 150 to 200nm range, depending on conditions. Also, noise levels are very good, even with no sound insulation. Overall reliability has been excellent. I now have about 1400 hours on this block and drive with no significant problems ever. Just make sure you are properly "zinced" and watch them carefully to prevent corrosion.

Con's:
Again, access to the lower end of the motor could be a lot better. My motor is carbureted, and I do wish for better efficiency. At low speeds (under 7-8 knots) the boat does "wander" a lot, like most single engine deep V hulls, but I have heard a Bravo 3 drive eliminates a lot of that (I have never run one). I am at the number of hours on this drivetrain now where I am looking at repower options and think that a Yanmar diesel I/O set-up (315 hp) will probably meet all of my needs the best. I believe there is another member on this site with that drivetrain, but forget his name. Weight aft is an issue with any of the old 23's; however, I only get really heavy "puddling" with an full load of fuel and 2 guys on the same side of the boat.

One last thought is that put Mercury Kiekhafer 280S "K-Plane" trim tabs on my boat a few years ago. They may be a bit overkill, and you can "overtab" with these if you get careless, but they mad a huge difference in the heavy water ride, and high speed smooth water handling of the boat.

Hope this helps with your decision. Please e-mail me if I can be of further help.

Chris

barnacle · #9 09-11-2003, 07:47 PM

We sell Volvo Penta and MerCruiser Packages. Both companys use GM engines. We have had no problems with the GM engines at all. IT must be a auto problem. As for which package to use is a hard call to make. If your boat came in we would try to push you on the MerCruiser 5.7 Horizon with the Bravo One Drive. The 454 is not offered anymore and is replaced by the 8.1 which is a great package but brings the price up. I like MerCruiser over Volvo due to there are plenty of MerCruiser dealers out there.You can always find a shop. Volvo does not have a large dealer base. This means when you need work done you may have a problem finding someone to work on it. Parts are also much more than MerCruier Parts. I would go the 5.7 but if you have the money be sure to check out the 8.1.

abl1111 · #10 09-11-2003, 08:42 PM

As usual, thx guys ! Joe, beleive it or not, I am still looking into the Bravo II drive...

The Bravo III scares me w/ electrolysis, especially since I will be keeping her in the water all the time. What can you tell me about the Mercathode system ? Does it need to be 'plugged in ' to electric when not at use and at the dock or is solely hooked to the boats batteries ?

Lastly, what motor and drive combo would a "351" be ? I know it's a Ford, but what do you guys think of that motor and what drive options are there ? Better than Mercriser/GM ?

As you can see - I'm all over the map - at least, at this point, I know it'll be an i/o !!!

- Alan