310 Santego 5.0 liter twins

[Donald Claypoole]

Hi there and so I'm new and still investigating this boat, and may have a really STUPID question...I've just discovered that port is replaced and approx. 7 years newer than starboard. Starboard appears original and has a Rochester quadra-jet setup with spark arrestor. Port has a LARGE Holley double pumper and just a cleaner. The stupid question...this is not normal is it? I'm under the assumption that the setups should be identical. That stated, the engines perform differently and planing is difficult; synchronization is almost impossible. I thought the linkage needed adjusted. Am I on track in thinking I need to replace the port carb? If so, any thoughts/advice on the best setup? The stock(starboard Q-jet idles better and sounds better but doesn't have great response. Port is pretty jumpy and runs a little hotter(160). Advice? I'd like to get out and run, but don't feel safe. Thanks.

[tomschauer]

First, get a flame arrestor on that holley.
Second, I would look at one engine at a time. Start with the port, if its running rough. Not sure about your engine knowledge, but is it a rough idle or did some install a performance rebuild with a steep cam? If your not sure have someone do basic tune up procedure on both motors. Check the timing, and verify the firing order on the newer engine. They both should have electric ignition so no dwell to check, but timing advance would also keep you from planning.

[waybomb]

Oh boy.
Sounds like somebody was extra cheap and installed a non-marine engine.
And did a poor job of it.
If the other engine grenades, what will you put in? You have no idea what the po idiot installed on the other side.
If walk away from this one. Who knows what other stupid things they did.
Your call. If the vessel is cheap and you can buy a new reman like the original, install it, and still be at what the vessel done right is worth, may be worth a chance.

[Donald Claypoole]

Thanks for the replies. More info-the second owner paid a bill of 2,100 for Mercruiser engine to a dealer in UP Michigan back in 2001. Also by looking at it, it's a marine engine, stock, pulled from another unit.....I'm going to get block numbers and carb information tonight, but it looks like a dealer did the job. To answer Tom's comment-both engines start, run and idle really well, very smooth, but port wants to sound and rev faster. Timing is good and the idle isn't lopey at all. Both crankcase oils are spotless. Everything "looks" stock and very clean. Absolutely going to pull the Holley and put a spark arrestor on a new Q-jet even though it'll probably be a dog. Fred-I own this problem outright...the PO's needed to pay bills so I thought was stealing it from them. Wrote a good contract and everything was replaced or re-installed on their dime. And I'm fairly convinced they had NO mechanical knowledge but drove it anyway. As for me, I'm handy but not a mechanic. My concern is if one engine is slightly outperforming the other, am I safe to cruise? I'll find out tonight; I need to see if they'll sync up on plane. Maybe I'm just nitpicking? But I want both engines to perform the same. Thoughts on carb setups on these 5.0 mercs would be appreciated! And no idea what I've got for props..

[Donald Claypoole]

Well, the marina mechanic had the quickest and best solution to install a two barrel manifold and Rochester on port; waiting on the linkage now. The Morse Teleflex controls have been adjusted as best he can get. Port is most definitely newer and he says approx. 40 hp more. I should have been more thorough and had an engine survey done. Won't happen again.

[km1125]

What do you mean by the one engine having "just a cleaner"? If it was not a spark arrestor (perhaps just a different type?) then I'd be shocked if a marina mechanic actually put that engine in.

I would not replace a 4bbl with a 2bbl. You could lose a lot more performance than you think. I'd either replace the Holley (and perhaps intake) with a like-minded Rochester, or I'd replace the Rochester (and perhaps intake) with a similar Holley. Without specs on the engines though, you may never get them the same. Depending on how far they are really off... I might just deal with the difference until I opted to replace/rebuild one of the engines.

Where did he come up with the "approx 40 HP more" calc?