Low Top End GT40

63 Skier wrote: [QUOTE=TRBenj] Prop down 1/2" and keep running it. I wouldn't touch it unless you really had the desire to do an engine rebuild. 43mph out of a 21' Sport does not seem out of family, especially since you are a little over propped.

From 63 Skier "Agree completely. Paul, in an earlier post you said "I really have no issues with how the boat runs". You are really so close to expected performance for that boat that it's possible you could do a full rebuild and not see any difference. If you read the props threads you probably saw that these boats seem to vary by 2-3 mph with no obvious mechanical reasons for it."


After reading this thread, what I get out of it is that you're
happy with the way the boat runs,
had a lot of good family time in it
it doesn't have any other issues
you're new to working on engines (comments like attempting to replace a distributor      cap and rotor make me think this)
you're saving for a new house

So like everybody says leave it alone and drive it.

If you want to get some first hand experience find a dirt cheap (hundred bucks or so) junkyard engine like a 302 or 351. It doesn't need to run. And get a book on rebuilding a small block Ford.

Get yourself an engine stand and have a blast taking it apart and doing plenty of hands on learning as you go. You might even want to put it back together again You gotta be careful though, things like this can get contagious and you'll be looking for more "projects"   

It's one thing to read about it and another to actually have all the pieces right in front of you.

You'll figure out what tools to buy along the way and be much more comfortable when you decide to tear into the boat engine sometime in the future

KenO

470, 1442 or 654 are all candidates with 15" pitch.

TRBenj wrote: Prop down 1/2" and keep running it.

Any prop suggestions? ACME 1442?

Don't touch it, meaning don't touch it. No snake oil (ever).

Propping down will ease the load on the engine and return better performance. Win/win.

63 Skier wrote: Also, I don't know how much you get out on the boat but there is nothing better than skiing on it as much as you can, putting a load on it and putting hours on it, to clean up a very mild ring problem.

This is the advice I got last year when I bought the boat. This season I have done about 50 hours, 20 of which were wakeboarding without any change, hence me trying to go with the snake oil.

I am mostly motivated to learn as much as possible. I have learnt so much this year thanks to this site. Mostly simple stuff but I knew nothing about it a year ago. I've change spark plugs, fuel filters, impellers, oil, Installed perfect pass, wet sanded and buffed gel coat. done gel coat repair, replaced relays and IACV, removed a stuck propeller, lapped a new prop, cleaned throttle body and spent loads of time with my family on the lake. It's been a great year and I guess I am just looking for some projects for the winter.

I would like to rebuild the engine next year after I have bought a new house (hopefully with room to work on the boat). I was hoping there were some thing worth working on this winter to see if I could get things running a little better.

TRBenj wrote: Prop down 1/2" and keep running it. I wouldn't touch it unless you really had the desire to do an engine rebuild. 43mph out of a 21' Sport does not seem out of family, especially since you are a little over propped.

Agree completely. Paul, in an earlier post you said "I really have no issues with how the boat runs". You are really so close to expected performance for that boat that it's possible you could do a full rebuild and not see any difference. If you read the props threads you probably saw that these boats seem to vary by 2-3 mph with no obvious mechanical reasons for it.

If you are trying snake oil, I'd put my vote in for Marvel Mystery Oil. Add a bit to the next few tanks of gas. Also, I don't know how much you get out on the boat but there is nothing better than skiing on it as much as you can, putting a load on it and putting hours on it, to clean up a very mild ring problem. I can't imagine with the compression numbers you listed that you have a cracked ring, seems more likely just some rust or cylinder wall scuffing. My usual disclaimer, I could very well be wrong!

Paul,
The obvious cheap simple way is to try a "snake oil" I don't think you have much to lose however, if the problem is broken rings, the stuff won't weld them back together!
Hey, even Autozone sells the Restore!!!

your outside of my pay grade with the GT-40 questions, but I assume that the intake manifold is the biggest difference, and all the rest is just bolt on stuff and sensors....   Mine has a carb, so no personal experience.

I am doing the install and swapping over the tin on my motor (intake, oil pan, timing cover and other external items)       - One of the Spokane builders I checked with could do the whole motor assembly and rebuild for 2500 (including tin), but it would not have been a roller motor, so I am not sure of the straight $ comparison, but if you can wrench, the accessory mounting part is not too difficult as long as you have the tools and time.


- deciding on how to proceed is a process of counting costs,   I figure if the bottom end needs work, you'll probably want to do a valve job on the heads, and make sure they are flat and not cracked...   reworking heads is expensive (~3-400 is a guess) so I am not sure that you're money ahead to save them when you can get a long block for a similar price, and all the work is done. One good thing about a long block is that all the calculations are done, you wont have to worry about compression ratios, rocker heights, cam durations etc, its done. You may be able to run the heads as they are, but that decision is money based, and I don't know your situation.   I too thought about the short block route, and the long block just made more sense to me.

Dreaming wrote: Engine should arrive today or tomorrow.     Since your on the right coast, you might check into Rapido Marine,   it looked like they could do a marine 351 long block for about 1500+ shipping.   Might be more with GT-40p heads, if they can do that. Michigan motors was another name that came up during my search, but I think they were more expensive.

Are you paying somebody to do the install?

What does that cost?

Dreaming wrote: cost is dependent on your local area rates, and the work that needs to be done.    you tackling the tear down and assembly will help your budget a good deal.    My Machine shop quoted me 1500+ parts for this work, I assume that is a bit on the steep side as they are well known around here for performance builds, and they had an 8 week backlog. (translation, they didn't need my one off 351 build to keep them busy, especially with the racing season coming to an end in the next few weeks)     All in, I spent 2300 (including shipping and tax) on a roller long block, gt-40.   While I was interested in doing the build work myself as well, time and cost were prohibitive to me, I figured I'd spend more than 800 in parts and tools to get this thing right in my garage, and many hours that I should be doing something else, so for me, experiencing the build didn't make sense.     If it runs now, and you can get another season out of the motor, I don't see a lot of reason not too, I would venture that you'll probably purchase a long block if you're budget conscious on getting the new engine.

Ah yes, I was reading your post as your situation was similar to mine. Do you have the engine yet? Have you installed it?

Dreaming wrote: I would certainly plan on an engine rebuild...   It seems to me that this is inevitable.

I definitely plan on rebuilding the engine but as stated above (unless I get a nice bonus from work) I'd rather wait until the end of next year to get this fixed. Hopefully I don't do anymore damage along the way.

Maybe I pull the engine at the end of the season and bring it home and see what I can get done. Apart from the cost my second biggest issue is find a place to work on the engine. I don't have much room in my current garage and I'd really like to try do this as much of the rebuild myself.

Ball park what would this cost for me to get somebody to fix this. I'd guess 2k to 3k does that sound about right?

Edit: Just to clarify, when i say do it myself, I mean the take apart and put it back together parts, with a machine shop doing the difficult work.

Yes, I did confirm it was 5 degrees at all RMP with the spout removed.

Compression numbers are as important as the difference between the numbers but the compression is low on all cylinders. I am sure I'd see great improvement from a rebuild.

Oil pressure is 60psi at both idle and speed.

I have VR1 20W-50 in there.

Thanks David, It's good to know I can keep running the engine, without doing major damage. For what I use the engine for it runs great. I haven't noticed any excessive oil burning or any other issue besides low top end discussed above.

I would like to fix the engine at some point and learning about all this and how to do it is a big reason I bought the boat but knowing I can put it off until I am ready is great.

I agree if I was going to do something I'd rather do it all then just try get the one piston done.