getrdunn

iTrader: (7)

Did you post hours yet. (Apprx if no or non working hour meters). As mentioned start with leak down when able. Even a simple compression test can red flag. Just depends on how far you want to go with your refresh but it sounds like it's about that time. What could be minimal cost now could easily turn into expensive down time when you want to enjoy your boat the most. You mentioned your not able to R&R engines. It's not as difficult as it might seem. I've used the old oak tree more than once. Not ideal considering twins... Just gotta be patient and a healthy hard wood tree with a woody. All depends on your budget but it kinda sounds like your trying to get a few more ponies with minimal cost. Understandable but not always reality once you start dissecting.

Helmwurst

About 560 hours. Very strict about maintenance. Considering the engines still seem to be running pretty strong, I am guessing, I have some valve stem seals gone, carbs in need of some attention to begin with. Will know more after testing. Oak tree wont work for me. If needed, will just find someone who has an inside shop to rent or hire out the R/R part. It would suck to do that at the beginning of the season, but it would only be for a month if machining can be turned around in a couple weeks. Besides, got a floating living room to chill out on until the motor work is done.

Baja Rooster

iTrader: (1)

You may do well to toss the current intakes for some Edelbrock air gaps and Quick Fuel carbs. I don't know what the stock manifolds are but you can search about the Air gaps, and just keeping the carbs cooler has benefits in themselves.

Griff

This time of year, its highly unlikely that you're going to find anybody that can do the machine work anytime soon.
In order to upgrade the cam, you will need to go with the Gil exhaust.

getrdunn

iTrader: (7)

560 hours on a well maintained marine engine is getting near that time for a refresh and not that costly assuming everything is straight and or round. If bearings, cylinders, pistons etc show no unusual wear the cost should be pretty reasonable. I've seen well maintained marine engines go many more hours before rebuild. My offshore experience has typically been around 400/450 hours. It's all kind of a gamble however you might get lucky with just having the heads refurbed and some aftermarket bolt parts including exhaust if considering much of a cam swap as griff mentioned. Doing it all can get quite costly in a hurry. You might get away with another season or two on bottom end. Ya it kinda sucks to spend a fair amount of money on a basic refresh/rebuild and see no gains but is what it is. You definately need to make that call but if it were me being 100% honest considering time of year I'd go for the HP and go have some fun and see the gains. Intakes, carbs, cams and some good used exhaust.

Assuming you have to pull engines for a cam swap at the very least pull the pan of one or both of the engines and check a couple of main and rod bearings for wear. Typically the bearings furthest from the pump wear first. Check the pan and oil for any unwanted goodies. That would determine what route you choose to go.

Ive had a couple boats I drilled holes in the rear bulkhead for cam removal and install. When it's all said and done it's easier to just pull engines but does come in handy. Heck I've changed cams on the water. Literally..

put an ad in on wanted section for some good used Gil's, EMI thunders, Stainless marines etc.
Ill probably get bashed a bit for not opting rebuild first but like I said you can always determine after oil pan removal.

thirdchildhood

iTrader: (6)

Can't an auto shop do the machining? They are very slow right now.

Helmwurst

I actually have a 2 near new sets of Gil/Mercruiser exhaust that came off of a pair HP450's same as the 500's. Been sitting under my stairwell in bubble wrap for several years. No need to cut holes in the firewall, you could pull the cams, install new bearing and cams, without pulling the engines, but I would never do that w/o doing a complete block inspection etc. We'll see how the diagnostics go and figure out from there. I really appreciate the input, gives me some talking point with the guy when he comes to test everything. I know of at least 4 boats in my cove that he has rebuilt the power in over the past 4 years.

getrdunn

iTrader: (7)

There you go OP. Snatch them up. Would be a great addition to your upgrading.

Griff

He is at LOTO, and the all shops in the area are pretty much marine and auto. Its Spring and everywhere will most likely be backed up.
Then you will have the surge of people who will have a failure on their first run or two in the Spring who flood the shops.

thirdchildhood

iTrader: (6)

Ah, everything here in Michigan is on lock down and mechanics are being laid off. The shops are still mostly open though but with no work.