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I OWN A1989 27 LUHRS ALURA. I NEED TO KNOW WHAT THE

I OWN A1989 27...

I OWN A1989 27 LUHRS ALURA . I NEED TO KNOW WHAT THE REDUCTION RATIO IS ON O.E.M TRANSMISSION AND ORIGIONAL SIZE AND PITCH FOR THE PROP..SINGLE SCREW LH WHEEL..CAN YOU HELP ME?

Mechanic's Assistant: Sometimes things that you think will be really complicated end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Tell me a bit more about what's going on so the Marine Mechanic can help you best.

BOAT HAD BEEN REPOWERED W MERCRUISER 350 GM BEFORE PURCHASE IN 2011. I HIT A SUBMERGED LOG AND LOST PROP, SHAFT AND RUDDER BUT MANAGED TO KEEP HER AFLOAT..HAD HER REPAIRED AND HAVE HAVE HAD GREAT LUCK SINCE.YEAR BEFORE LAST I REPLACED CARB W 600CFM EDELBROCK AND SHE RAN GREAT. LAST SEASON SHE STARTED N RAN GREAT AT LOW RPM (UNDER 2000RPM) BUT STARTED TO BACKFIRE AND BLOW WHITE SMOKE FROM ONE SIDE OF EXHAUST THEN THE OTHER SIDE. NO RHYME NOR REASON AND SWITCHED SIDES SPORADICALLY..SHE ALSO CUT OUT AND STALLED WITHOUT WARNING. REPLACED DIST CAP N MODULE STILL CUT OUT N DIED. REPLACED DISTRIBUTOR, COIL, AND WIRES. RUNS GREAT TILL 1800-2000 RPM. THEN BACKFIRESN BLOW WHITE SMOKE. I SHOULD MENTION THAT I CHANGED THE HEAT EXCHANGER AND HOSES YEAR BEFORE THIS PROBLEM AROSE N RAN ALLYEAR WITHOUT ISSUE. I AM NOT LOSING ANY ANTIFREEZE AND OIL IS CLEAN AS A WHISTLE. THERE IS NO WATER IN OIL NOR OIL IN MY COOLING SYSTEM..MY MECHANIC,WHO HAS WORKED ON THE BOAT SINCE I BOUGHT IT THINKS MY PROP MAY BE PART OF THE PROBLEM SO IM DOING THE LEGWORK. HE ALSO THINKS MY ELBOWS MAY BE THE ISSUE I HAVE GOOD COMPRESSION HOWEVER THE ELBOWS ON THE MANIFOLDS DO RUN HOT. HE WANTS TO KNOW OEM SPEC FOR PROP N RATIO FOR TRANSMISSION TO RULE IT OUT. THANK YOU

Mechanic's Assistant: Sometimes boat issues seem like they'll be really complicated, but end up being easy to fix. The Marine Mechanic I'm going to connect you with knows all the tricks and shortcuts. Is there anything else the Marine Mechanic should be aware of?

THINK IVE COVERED ALL OF IT THANK YOU

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Answered in 1 day by:
1/21/2018
Boat Doc
Boat Doc, Boat Enthusiast
Category: Boat
Satisfied Customers: 244
Experience: Expert at Just Answer
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Hi, sorry for the delay. Normally the small block boats were rigged with a 1.5 to 1 gearbox and could usually run a 15X15 three blade wheel. If the boat has been repowered it may have had a different gearbox at the same time, but that was fairly standard.

Boat Doc
Boat Doc, Boat Enthusiast
Category: Boat
Satisfied Customers: 244
Experience: Expert at Just Answer
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Customer reply replied 6 months ago
Thanks boat Doc! Very helpful. Now, having read my entire email describing my boats symptoms, can you think any reasons she acts up as described other than prop issue? Why would it start n run great at low rpm n breakup at anything over 1500-1700 rpm? As stated carb was rebuilt, distributor, coil n wires replaced this year. Heat exchanger replaced year before. No oil in coolant and no coolant in oil. No loss of coolant or oil. Both are squeaky clean. When I put her in gear against the dock, I can get 3200 rpm without issue. Do it in open water and she starts breaking up and blowing white smoke at 15-1700 rpm?

B​ackfiring is normally indicative of a lean condition. Did this engine ever run well with the new carb?

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Customer reply replied 6 months ago
Ran great season before last when it was installed new. I did have backfire issue at the end of that year. Mechanic who installed it said it was a timing issue but changed jobs before it was put away for the year. Following spring I was told the backfire issue was due to bad modulator in distributor and it was replaced. That’s when I had dist, coil n wires. Prob persisted. Rebuilt carb. Problem persists.

I would then check all the valves for adjustment. One or more could be floating at higher loads.

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Customer reply replied 6 months ago
Thanks. I’m a month or so away from uncovering the boat. In order to get to valve train I need to pull floors risers n manifolds due to space constrictions. That said I’ll probably pull heads n do a valve job while we’re in there.
Is there anything I should look for when we pull elbows or any suggestions for eliminating the exhaust system as a partial cause for the poor performance I’m experiencing? Thank you

Well, if you see evidence of water leakage down the risers that would definitely be cause for concern. At that point I would perform a compression test to see if any cylinder is down (rusted valves). If you choose not to do the valve job at least carefully inspect all springs and make sure no valve is noticeably misadjusted ( a sticking lifter could cause your issue also).

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Customer reply replied 6 months ago
Ya. No sense in going thru all that n not doing a valve job, I’m thinking. Thanx again. Right now I’m pulling apart a microwave that fails to cook. I hate winter

I'm with ya!

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